tag:theconversation.com,2011:/ca-fr/topics/antigen-test-87648/articlesAntigen test – La Conversation2024-03-01T13:33:07Ztag:theconversation.com,2011:article/2216032024-03-01T13:33:07Z2024-03-01T13:33:07ZCOVID-19 rapid tests still work against new variants – researchers keep ‘testing the tests,’ and they pass<figure><img src="https://images.theconversation.com/files/575188/original/file-20240213-26-dfzfvf.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4707%2C2718&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rapid tests are inexpensive, easy to use and give fast results, usually within 10 to 15 minutes.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/negative-test-result-by-using-rapid-test-device-for-royalty-free-image/1322901789?phrase=rapid+home+testing+covid&adppopup=true">Violeta Stoimenova/E+ via Getty Images</a></span></figcaption></figure><p>By September 2020, just six months after COVID-19 triggered shutdowns across the U.S., it was clear that <a href="https://doi.org/10.1140/epjp/s13360-023-03719-6">SARS-CoV-2, the virus that causes COVID-19, had mutated</a> from its original form. </p>
<p>The question quickly arose whether <a href="https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/understanding-home-otc-covid-19-antigen-diagnostic-test-results">existing rapid antigen tests</a> could detect newly emerging variants.</p>
<p>Using clinical samples obtained from diagnostic labs throughout the U.S. from 2020 to 2023, the National Institutes of Health, through its <a href="https://doi.org/10.1109/OJEMB.2021.3116490">Variant Task Force</a>, analyzed the effectiveness of more than 100 rapid antigen test kits on over 300 variants. The vast majority of the kits were able to detect new as well as prior previously known variants.</p>
<p>We are a team of researchers who have spent the past few years <a href="https://www.nibib.nih.gov/covid-19/radx-tech-program">researching COVID-19 tests</a> for their accuracy and performance. We understand why the public may still have questions about whether these tests are reliable, particularly as new variants continue to appear. </p>
<p>Here are answers to some of those questions:</p>
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<figcaption><span class="caption">As of early March 2024, the JN.1 variant is responsible for nearly all COVID-19 cases nationwide.</span></figcaption>
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<h2>Do these tests work?</h2>
<p>There are <a href="https://theconversation.com/whats-the-difference-between-a-pcr-and-antigen-covid-19-test-a-molecular-biologist-explains-170917">two major types of tests</a> for the detection of SARS-CoV-2. </p>
<p>The first, called a <a href="https://www.mayoclinic.org/tests-procedures/covid-19-diagnostic-test/about/pac-20488900">RT-PCR test</a>, is more than 95% accurate for detecting the virus. These were the tests that most Americans were given at drive-through and walk-in testing sites early in the pandemic. The vast majority are now done at a doctor’s office or clinic, though there are <a href="https://cuehealth.com/">some home PCR tests</a>, which typically cost five to 10 times more than rapid antigen tests.</p>
<p>The other type is <a href="https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/understanding-home-otc-covid-19-antigen-diagnostic-test-results">an antigen test</a>, commonly known as a rapid test, with an accuracy rate of more than 80%. Most of these tests are sold over the counter at supermarkets and pharmacies. </p>
<p>Rapid antigen tests are relatively inexpensive, can be used without prior training and give quick results, typically within 10 or 15 minutes. One drawback is that they are less accurate than PCR tests, especially early in an infection when there is less virus present in the body.</p>
<p>Despite these inherent limitations, our team has demonstrated that these tests <a href="https://doi.org/10.7326/M22-0760">perform as well in 2024</a> as they did earlier in the pandemic, when different variants were circulating – even though our initial study was completed in January 2022. That’s because the virus protein detected by antigen tests has not changed much over the last two years, unlike other parts of the virus that have undergone many mutations. Another study, which tested the accuracy of rapid antigen tests from 2020 to 2022, <a href="https://doi.org/10.1016/j.isci.2022.103968">found similar results</a>. </p>
<p>That said, researchers like us continue to “test the tests,” both in computer simulations and in the lab, to detect new SARS-CoV-2 variants. </p>
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<a href="https://images.theconversation.com/files/578991/original/file-20240229-16-t016d9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Researchers wearing masks and other protective gear sit under tents collecting samples during a COVID-19 testing study." src="https://images.theconversation.com/files/578991/original/file-20240229-16-t016d9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578991/original/file-20240229-16-t016d9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578991/original/file-20240229-16-t016d9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578991/original/file-20240229-16-t016d9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578991/original/file-20240229-16-t016d9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578991/original/file-20240229-16-t016d9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578991/original/file-20240229-16-t016d9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">UMass Chan Medical School research staff members enroll participants in a COVID-19 testing study in Worcester, Mass., in the fall of 2020.</span>
<span class="attribution"><span class="source">Nathaniel Hafer</span></span>
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<h2>I have symptoms. When should I take a test?</h2>
<p>If you have symptoms, take a rapid test <a href="https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/testing.html">as soon as possible</a>. If you test positive, you can be reasonably certain that you’re infected. If you’re negative, wait two days and test again. </p>
<p>This waiting period is important because it takes a few days <a href="https://doi.org/10.1093/infdis/jiab337">for the virus to build up</a> to <a href="https://doi.org/10.1371/journal.pbio.3001216">levels that are detectable by the rapid test</a>. Recent research has shown that the time it takes for this to happen is <a href="https://doi.org/10.1093/cid/ciad582">slightly longer with the omicron family of variants</a> compared to variants from a few years ago.</p>
<h2>I was exposed, but have no symptoms. When do I test?</h2>
<p>If you’ve been exposed to somebody but don’t have symptoms, the current recommendation is to wait <a href="https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/testing.html#:%7E">four to five days before taking a rapid test</a>. If you’re negative, wait two days and then test again. </p>
<p>If you’re still negative, take a third test two more days later. This is the best way to <a href="https://doi.org/10.7326/M23-0385">detect COVID-19 infection without symptoms</a>.</p>
<p>It’s also recommended that you take a rapid test as close as possible to the time you’re visiting someone who is at risk for getting sick, especially if you think you may have been exposed.</p>
<h2>When am I contagious?</h2>
<p>Most people who have symptoms and test positive are contagious. If you no longer have symptoms and are no longer testing positive, it’s <a href="https://doi.org/10.1001/jamanetworkopen.2022.25331">likely that you’re not contagious</a>. </p>
<p>But there are some exceptions to this general rule. It’s possible to be infected, have no symptoms and be contagious. This is especially true early on in a person’s infection. </p>
<h2>Should I swab my nose or throat?</h2>
<p>The best advice is to follow the instructions that come with your test. For antigen tests in the U.S., this means taking a swab of your nose. </p>
<p>Although one study from Denmark reported that <a href="https://doi.org/10.1001/jamanetworkopen.2023.44295">antigen tests were more sensitive</a> when a health care provider swabbed the throat, the same study said that when a person swabbed themselves, nose samples were more accurate than throat samples. Other studies have shown <a href="https://doi.org/10.7326/M22-0202">that swabbing the throat</a> <a href="https://doi.org/10.1101/2022.02.08.22270685">was no better than swabbing the nose</a>. </p>
<p>A new program <a href="https://www.nih.gov/news-events/news-releases/home-test-treat-program-extends-nationwide">funded by the National Institutes of Health</a> and rolled out in late 2023 – the <a href="https://www.test2treat.org/">Home Test to Treat study</a> – offers free testing, telehealth and treatment for COVID-19 and the flu <a href="https://www.umassmed.edu/news/news-archives/2023/12/umass-chan-partners-with-expanded-federal-home-test-to-treat-program-for-covid-19-flu/">without leaving home</a>. To date, more than 60,000 people have enrolled. The study uses commercially available rapid tests and typically arrive a few days after they’re requested.</p>
<p>For those millions of Americans who are unable to travel, are without insurance, <a href="https://doi.org/10.1001/jamanetworkopen.2022.41144">don’t live near a clinic</a> or simply don’t want to expose others to their symptoms, this new program could help save lives.</p><img src="https://counter.theconversation.com/content/221603/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathaniel Hafer receives funding from the National Institutes of Health and the National Science Foundation. </span></em></p><p class="fine-print"><em><span>Anuradha Rao receives funding from the National Institute of Biomedical Imaging and Bioengineering and the National Center for Advancing Translational Sciences. </span></em></p><p class="fine-print"><em><span>Apurv Soni receives funding from the National Institutes of Health.</span></em></p>Research shows that rapid antigen tests are performing as well at detecting the most recent dominant variants as they did with the earliest strains in the COVID-19 pandemic.Nathaniel Hafer, Associate Professor of Molecular Medicine, UMass Chan Medical SchoolAnuradha Rao, Assistant Professor of Pediatrics, Emory UniversityApurv Soni, Assistant Professor of Medicine, UMass Chan Medical SchoolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2014062023-03-24T09:34:57Z2023-03-24T09:34:57ZCOVID testing led to new techniques of disease diagnosis: progress mustn’t stop now<figure><img src="https://images.theconversation.com/files/514637/original/file-20230310-142-f88cb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Covid-19 exposed critical shortcomings of existing diagnostic techniques</span> <span class="attribution"><span class="source">Michael Tewelde/Xinhua via Getty Images</span></span></figcaption></figure><p>In March 2020, weeks before the World Health Organization (WHO) declared COVID-19 a pandemic, its director-general Tedros Adhanom Ghebreyesus delivered <a href="https://www.who.int/director-general/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19---16-march-2020">a speech</a> in which he emphasised the importance of testing:</p>
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<p>… the most effective way to prevent infections and save lives is breaking the chains of transmission. And to do that, you must test and isolate. You cannot fight a fire blindfolded. And we cannot stop this pandemic if we don’t know who is infected. We have a simple message for all countries: test, test, test.</p>
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<p>The pandemic exposed critical shortcomings of existing diagnostic techniques. It revealed an urgent need for tests that are faster, simpler, cheaper and more scalable than existing methods, and just as accurate. </p>
<p>Three years on, the global face of diagnostics has changed. New techniques of disease diagnosis have been developed that can be applied to other emerging zoonotic pathogens such as “<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8367867/">disease X</a>” – a hypothetical infectious disease that has the potential to develop into a pandemic.</p>
<p>As a molecular scientist with a keen interest in veterinary disease diagnostics, I have closely followed developments in the diagnostic space since the start of the pandemic. These emerging technologies, together with conventional tests, have the potential to overcome bottlenecks in the current diagnostic procedures. By incorporating these tests into a country’s healthcare system, clinicians and policy makers are better equipped to practise precision medicine and to react to potential outbreaks.</p>
<h2>How the tests changed</h2>
<p>The first diagnostic tests for SARS-CoV-2 (the virus that causes COVID disease) used established molecular techniques such as reverse transcription polymerase reaction (RT-PCR). These techniques detect and identify organisms by amplifying their genetic material millions of times. Running the tests however requires trained technicians and expensive equipment.</p>
<p>As the pandemic became more severe, other ways to test for the virus had to be developed. Substances and compounds needed to effectively run diagnostic tests were in short supply and many countries did not have the kinds of sophisticated laboratories needed for the existing tests. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9178421/">Low- and middle-income countries</a> like those throughout the African continent had limited finances too and not enough trained specialists to handle the demand.</p>
<p>Isothermal amplification techniques helped to address the need. This is a simple process which rapidly and effectively amplifies DNA and RNA (genetic material) at constant temperature. </p>
<p>Immunological assays also helped. These tests can be used on-site or in the lab and are able to detect specific molecules such as antibodies and antigens. Antibodies are generated in a person’s body when a foreign molecule (antigen) invades the body.</p>
<p>These cost-effective tests provide rapid results and can be used on a big scale even where resources are scarce. The <a href="https://www.mdpi.com/2075-4418/11/2/182">major challenge</a> of these tests is that they are less accurate. Unlike molecular tests, which amplify the genetic material of the virus, immunological assays do not amplify their protein signal. This makes them <a href="https://www.science.org/content/article/coronavirus-antigen-tests-quick-and-cheap-too-often-wrong">less sensitive</a>. The risk is high that an infected person might incorrectly be told that they don’t have the virus.</p>
<p>The global diagnostic community realised it was time to look at methods that were as accurate as conventional molecular tests but could be used outside laboratories and on a large scale. </p>
<h2>Big strides</h2>
<p>Scientists needed a new generation of rapid, accurate, accessible and affordable diagnostic tests. The National Institutes of Health in the US set up the Rapid Acceleration of Diagnostics programme (<a href="https://www.nih.gov/research-training/medical-research-initiatives/radx/radx-programs">RADx</a>) in 2020 to fund innovative point-of-care and home-based tests and to speed up the development, validation and commercialisation of these tests.</p>
<p>One particularly interesting change in this space is the use of <a href="https://www.sciencedirect.com/science/article/pii/S1046202321000992">CRISPR</a>. The technology was previously known for its use in gene editing. But now it has revolutionised diagnostics with the launch of SHERLOCK and DETECTR, two innovative CRISPR-based kits used for the detection of SARS-CoV-2. These are particularly sensitive and specific and provide a visual colour readout using a commercially available paper dipstick, making them suitable for use as a point-of-care test. </p>
<p>The versatility of these techniques enables researches to apply the same principles to the detection of other infectious diseases too.</p>
<p>There have also been advances in using <a href="https://www.mdpi.com/1467-3045/44/10/325">biosensors</a>, <a href="https://luminostics.com/">nanotechnology</a>, <a href="https://nicoyalife.com/blog/nicoya-covid-19-diagnostic-test-2/?utm_campaign=COVID-19">smartphone-based tests</a> and <a href="https://www.nature.com/articles/s41591-020-1123-x">wearable technologies</a> for diagnostics.</p>
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Read more:
<a href="https://theconversation.com/what-is-crispr-the-gene-editing-technology-that-won-the-chemistry-nobel-prize-147695">What is CRISPR, the gene editing technology that won the Chemistry Nobel prize?</a>
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<p>Overall, in the past three years, the <a href="https://pubs.rsc.org/en/content/articlelanding/2023/lc/d2lc00662f">focus of disease testing</a> has moved from simple detecting and understanding to incorporating speed, efficiency and portability of the tests.</p>
<h2>Problems remain</h2>
<p>While there is a lot to celebrate in the diagnostic space, problems remain. There are barriers in developing and disseminating tests, particularly in poorer countries. <a href="https://www.finddx.org/wp-content/uploads/2022/12/20221210_rep_democratizing_testing_FV_EN.pdf">Fairer</a> access to quality testing and improved data sharing between countries is needed to eliminate the inequity in diagnostics.</p>
<p>The lack of resources to deliver a robust regulatory system in low- and middle-income countries also poses a serious challenge. Companies have less incentive to develop and commercialise products where there is weak regulation. Thus countries still depend on tests that are manufactured elsewhere. </p>
<p>As the world moves out of its pandemic response phase, it is likely that investment in diagnostics will fall. With a reduced need for tests, the economic return of investing in developing tests will diminish.</p>
<p>This is unfortunate as there are still so many healthcare challenges worldwide and unless disease surveillance is proactive, it won’t be possible to predict where the next pandemic might emerge from. The momentum created by the COVID pandemic offers an opportunity and should be used to build on the things that worked well in the diagnostic industry and to improve on the things that didn’t.</p><img src="https://counter.theconversation.com/content/201406/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Angelika Loots does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The pandemic spurred the diagnostics industry to consider aspects like scale, affordability, speed and portability of tests.Angelika Loots, Postdoctoral Fellow, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1766162022-02-17T13:58:04Z2022-02-17T13:58:04ZCOVID-19 self-testing: it’s time developing countries took the leap<figure><img src="https://images.theconversation.com/files/445655/original/file-20220210-19-xve0n8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">COVID self-testing is widespread in developed countries. </span> <span class="attribution"><span class="source">George Frey/Getty Images</span></span></figcaption></figure><p>Laboratory testing plays a critical role for diagnosis of COVID-19. It’s the cornerstone of the global public health response, informing control measures and preventing transmission of SARS-CoV-2. </p>
<p>The basis of infectious disease testing depends on the pathophysiology of the infection and the disease that it causes, the clinical course as well as the host immune response. </p>
<p>There are two types of tests for acute SARS-CoV-2 infection whether it is symptomatic or asymptomatic: COVID-19 PCR and antigen tests also called “lateral flow tests”. Both detect viral components, but differ in design and complexity. </p>
<p>COVID-19 antigen tests are a game-changer, even at this stage of the pandemic when the world is no longer hoping to achieve containment of SARS-CoV-2 but rather looking at mitigating strategies to prevent infection in those who face the biggest threat from the virus. </p>
<p>Antigen tests are cheap and quick. They can help identify infected individuals and interrupt viral transmission by quarantining infected individuals immediately. In South Africa the proportion of COVID-19 antigen tests compared to PCR remains low. In <a href="https://www.nicd.ac.za/wp-content/uploads/2022/01/COVID-19-Testing-Summary-Week-3-2022.pdf">week 3</a> of January 191,510 COVID-19 tests were done. Only 22.8% of these were antigen tests. None of these tests were done by individuals – this <a href="https://www.groundup.org.za/article/covid-19-it-time-allow-home-testing/">isn’t allowed</a> under the country’s regulations. </p>
<p>It is difficult to discern why countries in Africa have not taken up COVID-19 antigen testing. Access and price don’t seem to be the issue. The <a href="https://africacdc.org/news-item/new-guidance-to-expand-rapid-antigen-testing-for-covid-19-response-in-Africa-released/">Africa Centres for Disease Control</a> has even published clear guidelines on how to use them. But there is a lingering mistrust in test quality that has limited their use. </p>
<p>It is true that there are concerns about <a href="https://www.who.int/publications/i/item/antigen-detection-in-the-diagnosis-of-sars-cov-2infection-using-rapid-immunoassays">self-testing</a>. But, in my view, the benefits are substantial. Individuals are able to access cheaper and faster tests. This, in turn, helps limit exposure to those at risk of infection. Public health specialists in developing countries are putting <a href="https://t.co/1OWMfQWFY2">pressure</a> on authorities for greater use of antigen tests – particularly for self-testing to be allowed. </p>
<h2>The two tests</h2>
<p>COVID-19 <a href="https://link.springer.com/article/10.1007/s10096-020-03913-9">PCR tests</a> amplify viral gene targets and are very sensitive. Over 1000 commercial ones are now <a href="https://www.theglobalfund.org/media/9629/covid19_diagnosticproducts_list_en.pdf">available</a>. They are able to detect viral components slightly before symptoms start in infected individuals and many weeks after infection – even when there is no longer any risk of transmissibility. </p>
<p>The COVID-19 PCR tests have their drawbacks. For example, measures have been put in place – such as hospital admissions and travel bans – on the basis of positive results even though this hasn’t been strictly necessary. </p>
<p>COVID-19 PCR test performance depends on several factors. These include design, the clinical characteristics of the patient, timing of the sample, sample type and transport conditions and laboratory techniques. They are also expensive, technically difficult, require specialised staff and reagents, specimen transport and processing.</p>
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Read more:
<a href="https://theconversation.com/antibody-tests-arent-a-covid-19-panacea-but-theyre-a-useful-additional-tool-142516">Antibody tests aren't a COVID-19 panacea. But they're a useful additional tool</a>
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<p>For their part, COVID-19 antigen tests are immunoassay rapid diagnostic tests that have different viral antigenic targets and designs. </p>
<p>Rapid diagnostic tests are used extensively for the diagnosis of other respiratory infectious diseases like influenza in clinics, community settings and home-based self-testing. Most use a nitrocellulose membrane embedded in a plastic cassette which contains two lines. The one is a control line to inform that the test is working and the second is a detection line to indicate the presence of the virus. The reaction is based on coloured labels (nanoparticles) that change colour when they encounter the target.</p>
<p>COVID-19 antigen tests perform better when there is a high viral load and in patients that are symptomatic. They are usually positive from 5 and up to 12 days after onset of symptoms. They correlate with competent <a href="https://journals.asm.org/doi/10.1128/JCM.00469-21">viral replication</a> and thus transmission potential. </p>
<h2>Self-testing</h2>
<p>Self-testing with COVID-19 antigen tests was first <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-first-covid-19-test-self-testing-home">authorised</a> by the US Food and Drug Administration in November 2020 to allow symptomatic people and those that had COVID-19 contacts to test themselves. </p>
<p>By 2021 antigen tests and <a href="https://ec.europa.eu/info/live-work-travel-eu/coronavirus-response/public-health/high-quality-covid-19-testing_en">self testing</a> was firmly entrenched in most <a href="https://www.healthdirect.gov.au/blog/what-are-covid-19-rapid-antigen-tests">developed countries</a>. Their widespread use for self-testing has sparked a range of <a href="https://www.nature.com/articles/d41586-021-00332-4">debates</a>. They hinge on three issues: </p>
<p><strong>Is the test sensitive enough?</strong> </p>
<p>A test’s sensitivity is its ability to identify the infection if it is present and also not to miss infections. Sensitivity depends on the test design which in turn impacts its level of detection. Antigen tests differ in sensitivities. Some are excellent compared to PCR tests. </p>
<p><strong>Is the sample adequate?</strong> </p>
<p>Simplifying the sample type to include saliva – which is an easier and more standardised sample to access – has increasingly been the direction of <a href="https://www.medrxiv.org/content/10.1101/2021.02.17.21251863v1">most COVID-19 antigen tests</a>. </p>
<p><strong>Is the test result easy to read and interpret?</strong> </p>
<p>Reading a rapid COVID-19 antigen test visually may sometimes be difficult. Sometimes faint lines appear in the detection window and it is difficult to work out if the test is positive or negative.</p>
<p>Interpretation is also critical. This is particularly true with negative results. These may not definitively exclude infection. A retest may then be necessary. </p>
<p>In addition, interpreting the result correctly is complex even if clear instructions are provided.</p>
<p>In a large US <a href="https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2788656">study</a> on self-testing showed that 1 in 3 individuals misinterpreted their COVID-19 antigen result. The study found that clarity of the information given to the patients doing the self-testing via a variety of different formats was extremely important to a good test outcome. </p>
<p>Individuals in the study drew false reassurance from a negative results. </p>
<p>A recent study also showed that trained <a href="https://www.medrxiv.org/content/10.1101/2021.01.13.21249563v2.full.pdf">laboratory personnel</a> do the tests better than individuals. </p>
<h2>What next?</h2>
<p>It’s clear that there are a number of caveats to self-testing with antigen tests.</p>
<p>However, on balance, I still believe that they should be allowed more widely in countries like South Africa.</p>
<p>One reason is that the failure to authorise the tests is driving a thriving <a href="https://www.businesslive.co.za/fm/features/2022-02-03-why-covid-home-tests-remain-illegal-in-sa/">black market</a> in them. Many are of unknown quality. </p>
<p>Secondly, if used widely they could help control transmission risks as more people would know their status. </p>
<p>However, governments need to issue national guidelines and provide appropriate instructions.</p><img src="https://counter.theconversation.com/content/176616/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eftyhia Vardas does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>One of the consequences of the failure of developing countries like South Africa to authorise self-testing is that it is driving a thriving black market.Eftyhia Vardas, Clinical specialist Virology, Stellenbosch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1741482021-12-22T13:13:16Z2021-12-22T13:13:16ZBiden to expand access to at-home COVID kits: 4 essential reads on the critical role of rapid tests<figure><img src="https://images.theconversation.com/files/438738/original/file-20211221-19-pe5c55.jpg?ixlib=rb-1.1.0&rect=10%2C120%2C6699%2C4345&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Reflecting on the growing demand for at-home rapid COVID-19 tests.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/woman-performing-a-covid-19-antigen-self-test-at-royalty-free-image/1338929267?adppopup=true">Corinna Kern/Getty Images</a></span></figcaption></figure><p>President Joe Biden has <a href="https://www.nytimes.com/live/2021/12/21/world/omicron-covid-vaccine-tests">outlined plans</a> to massively ramp up COVID-19 testing in an effort to curb – or at least slow – the spread of the highly infectious omicron variant across the U.S.</p>
<p>In a <a href="https://www.cbsnews.com/news/biden-omicron-variant-speech-covid-19-watch-live-today-2021-12-21/">speech on Dec. 21, 2021</a>, Biden said he aimed to get out “as many tests, as quickly as possible” and said free at-home kits would be sent out to Americans beginning in January.</p>
<p>At the forefront of the push against the omicron variant will be new federal testing sites and the distribution of <a href="https://apnews.com/article/coronavirus-pandemic-joe-biden-health-jen-psaki-08ee41d8e7c0af1ad8b4dfb7b434ea61">500 million rapid tests</a>, free of charge, to the public. To enable the speedy rollout of tests, the White House committed to using the <a href="https://www.militarytimes.com/news/your-military/2020/03/19/what-exactly-is-the-defense-production-act/">Defense Production Act</a>, which allows the federal government to “allocate materials, services and facilities” from the private sector to meet the demands of the nation.</p>
<p>The focus on testing comes at a time of <a href="https://www.nbcnews.com/news/us-news/covid-testing-demand-spikes-ahead-christmas-lines-sites-rcna9140">high demand for kits</a> that diagnose infection. The arrival of the omicron variant has coincided with a desire by many to get tested before meeting up with loved ones over the holiday period, resulting in <a href="https://www.cnn.com/2021/12/19/health/covid-omicron-testing/index.html">long lines outside test sites</a> and a <a href="https://www.axios.com/coronavirus-testing-biden-omicron-christmas-8f8270d8-e192-40fd-ad40-b6391869f577.html">run on home kits</a> being sold at pharmacies.</p>
<p>Throughout the coronavirus pandemic, The Conversations’s team of health experts has been on hand to explain why testing is such a crucial part of the response. </p>
<h2>1) What exactly is a rapid COVID-19 test?</h2>
<p>The type of test that Biden is hoping to get into the hands of Americans is a <a href="https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html">rapid antigen test</a>. </p>
<p>Rapid antigen tests look for proteins from the virus that may be present in samples collected via saliva or a swab up the nostrils.</p>
<p>The tests are relatively cheap and quick, with results known in around 15 minutes. They are, however, not 100% reliable and can miss the early stages of COVID-19 infection. </p>
<p><a href="https://www.fda.gov/consumers/consumer-updates/coronavirus-disease-2019-testing-basics">PCR tests</a>, which are better at detecting low levels of the virus, are usually performed by a doctor or health practitioner – although some are available for home use – after which the samples are sent to a lab.</p>
<p>Like the rapid test, the first step in a PCR test is the collection of genetic material – again, saliva or nostril swab.</p>
<p>After that initial procedure, the sample is amplified through a sophisticated process that causes the test DNA to replicate until there are a billion copies of the original piece.</p>
<p>This allows for a very high level of accuracy, with the test being able to detect the tiniest presence of SARS-CoV-2, the virus that causes COVID-19.</p>
<p>But as <a href="https://profiles.umassmed.edu/display/14945561">Nathaniel Hafer</a>, an expert in molecular medicine at UMass Chan Medical School, notes, the <a href="https://theconversation.com/whats-the-difference-between-a-pcr-and-antigen-covid-19-test-a-molecular-biologist-explains-170917">PCR test has weaknesses</a> – a PCR test can cost up to US$100 or more, and results can take several days to come through.</p>
<p>It’s important to note that all tests are a snapshot at the time of sample collection and are much more likely to be accurate when a person is infectious. So people are encouraged to take multiple tests 24 hours apart.</p>
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<strong>
Read more:
<a href="https://theconversation.com/whats-the-difference-between-a-pcr-and-antigen-covid-19-test-a-molecular-biologist-explains-170917">What's the difference between a PCR and antigen COVID-19 test? A molecular biologist explains</a>
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<h2>2. Why rapid tests are important – especially now</h2>
<p>Despite PCR tests being better at detecting low levels of the virus, the antigen tests can be particularly useful at a time when many people need to get tested.</p>
<p>As Hafer notes in a separate article for The Conversation, <a href="https://theconversation.com/rapid-tests-play-a-crucial-role-in-curbing-covid-19-infections-especially-as-people-gather-for-the-holidays-173207">rapid tests are</a> “a welcome tool in society’s fight against the COVID-19 pandemic.”</p>
<p>He advises readers to take a test, be it PCR or antigen, as soon as they show symptoms of COVID-19. And the same holds true whether someone is vaccinated or not.</p>
<p>“The faster you can determine if you have COVID-19, the sooner you can isolate yourself, which helps prevent transmission to others,” he writes.</p>
<p>And even if someone gets a negative antigen result, it shouldn’t be assumed that they are in the clear. Anyone showing symptoms would be advised to have a follow-up rapid or PCR test.</p>
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Read more:
<a href="https://theconversation.com/rapid-tests-play-a-crucial-role-in-curbing-covid-19-infections-especially-as-people-gather-for-the-holidays-173207">Rapid tests play a crucial role in curbing COVID-19 infections – especially as people gather for the holidays</a>
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<h2>3) So how do you use a home testing kit?</h2>
<p>One of the big benefits of the rapid test is that it can be performed at home – no need for a lab setting or skilled lab technicians.</p>
<p>Zoë McLaren, <a href="https://publicpolicy.umbc.edu/zoe-m-mclaren/">a public health policy expert at the University of Maryland, Baltimore County</a>, explained how readers should <a href="https://theconversation.com/over-the-counter-rapid-antigen-tests-can-help-slow-the-spread-of-covid-19-heres-how-to-use-them-effectively-166869">go about using their home test</a>.</p>
<p>First off, plan ahead. </p>
<p>“It’s important to have a plan for what to do based on the test results. If you get a positive result, immediately take precautions to slow transmission, such as self-isolating, letting close contacts know about the test result and reporting the case to health authorities,” McLaren writes. Even when presented with a negative result, caution is advised, “and, if you have symptoms or a known exposure, it’s a good idea to do a follow-up rapid antigen or PCR test just in case the first test was a false negative.”</p>
<p>A second rapid test performed 24-36 hours after the initial test can help detect coronavirus cases that may have been missed the first time around due to an insufficient viral load, writes McLaren.</p>
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<strong>
Read more:
<a href="https://theconversation.com/over-the-counter-rapid-antigen-tests-can-help-slow-the-spread-of-covid-19-heres-how-to-use-them-effectively-166869">Over-the-counter rapid antigen tests can help slow the spread of COVID-19 -- here's how to use them effectively</a>
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<h2>4) And if you still can’t get your hands on a rapid test?</h2>
<p>Despite the massive planned rollout of rapid tests announced by Biden, there may well still be difficulties finding a kit. </p>
<p>Loss of smell or taste can be an indicator of COVID-19 infection. <a href="https://foodscience.psu.edu/directory/jeh40">John Hayes</a> and <a href="https://www.nursing.psu.edu/directory/rice/">Cara Exten</a>, both of Penn State, recount how a graduate student’s mother discovered recently that she could neither smell nor taste her habitual cup of coffee. She quarantined and got a rapid test, which came back positive.</p>
<p>The fact that she confirmed her suspicions by use of an antigen test underscores a key point: If you have the slightest inkling that you may have COVID-19, or been in contact with someone who has, it is advisable to get tested to know for sure.</p>
<p>“Using loss of smell as a COVID-19 test is far from perfect. But because a daily smell check is very specific, instantaneous and quite literally free, it is a highly useful screening tool,” write Hayes and Exten.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/daily-diy-sniff-checks-could-catch-many-cases-of-covid-19-150717">Daily DIY sniff checks could catch many cases of COVID-19</a>
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<p>.</p>
<p><em>Editor’s note: This story is a roundup of articles from The Conversation’s archives.</em></p><img src="https://counter.theconversation.com/content/174148/count.gif" alt="The Conversation" width="1" height="1" />
The Biden administration intends to distribute an additional 500 million at-home rapid COVID tests starting in January.Matt Williams, Senior International EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1727352021-12-12T14:46:19Z2021-12-12T14:46:19ZHow to use rapid testing to keep you and your family safe during the 2021 holiday season<figure><img src="https://images.theconversation.com/files/435754/original/file-20211206-23-1b6c5g4.jpg?ixlib=rb-1.1.0&rect=183%2C404%2C7627%2C5052&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rapid antigen tests are easy to use and detect whether your body is shedding the SARS-CoV-2 virus.</span> <span class="attribution"><span class="source">(AP Photo/Tsafrir Abayov) </span></span></figcaption></figure><iframe style="width: 100%; height: 175px; border: none; position: relative; z-index: 1;" allowtransparency="" src="https://narrations.ad-auris.com/widget/the-conversation-canada/how-to-use-rapid-testing-to-keep-you-and-your-family-safe-during-the-2021-holiday-season" width="100%" height="400"></iframe>
<p>This holiday season, we are all itching for a little bit of normalcy. For many, this means spending time with family and friends, and dropping the masks to drink eggnog. But even if you are fully immunized against COVID-19 (<a href="https://doi.org/10.1016/S0140-6736(21)02249-2">whether that’s defined as two or three vaccines is currently under debate</a>), the infectiousness of SARS-CoV-2, the virus responsible for COVID-19, means that you can still transmit the virus to others.</p>
<p>Vaccination is the <a href="https://theconversation.com/i-work-at-a-covid-19-vaccine-clinic-heres-what-people-ask-me-when-theyre-getting-their-shot-and-what-i-tell-them-167046">best way to protect yourself against COVID-19</a>. Even if infected, vaccinated people are less likely to have symptoms and more likely to have a mild course of infection. However, this means that you may not even know that you have SARS-CoV-2 (whether the Delta variant <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/variant.html">or Omicron</a>) and could unwittingly pass it on to someone else.</p>
<p>To protect the most vulnerable — including those who are immunocompromised, the elderly and kids who have yet to be vaccinated — rapid antigen testing (rapid testing) is an extra measure that can help you have a more normal holiday, if used correctly. As health-care professionals, we have been involved in rapid testing research and clinical use during the pandemic. Here are some common questions and answers.</p>
<h2>1. What is a rapid test?</h2>
<p><a href="https://www.ontariohealth.ca/sites/ontariohealth/files/2021-03/Panbio%20Onboarding%20Guide%20V1%20Feb%2017%202021%20EnglishTM.pdf">Rapid antigen tests</a> detect whether your body is shedding the SARS-CoV-2 virus. Rapid tests are very easy to use — so easy that an eight-year-old can become well-versed in the correct procedure and teach adults how to do it. </p>
<p>For most tests, you insert a stick resembling a cotton swab into each nostril for five seconds, roll it around and then mix it with a liquid solution. Then, using a dropper, you place the solution on a test kit (it looks like a pregnancy test). The result is ready in about 15 minutes. </p>
<figure class="align-center ">
<img alt="Components of a rapid antigen test: a swab, vial of reagent liquid and a test device." src="https://images.theconversation.com/files/435760/original/file-20211206-27-150t5rn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435760/original/file-20211206-27-150t5rn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435760/original/file-20211206-27-150t5rn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435760/original/file-20211206-27-150t5rn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435760/original/file-20211206-27-150t5rn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435760/original/file-20211206-27-150t5rn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435760/original/file-20211206-27-150t5rn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A rapid antigen test kit includes a nasal swab, a vial of reagent fluid and a test device.</span>
<span class="attribution"><span class="source">(Pixabay)</span></span>
</figcaption>
</figure>
<p>A rapid test differs from the PCR (polymerase chain reaction) test, which <a href="https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/medical-devices/testing/nucleic-acid-devices.html">measures amplified viral RNA</a>. PCR tests are generally more invasive. The sample is collected by a nasopharyngeal swab that requires sampling of nasal and pharyngeal pathways near the back of the throat. It takes longer to get results (hours to days versus minutes) and typically needs to be administered and processed by a health-care professional. However, the PCR test is the only choice if you are symptomatic and require a diagnosis at hospital or clinics. </p>
<h2>2. What does a rapid test actually tell you?</h2>
<p>A rapid antigen tests tells you if you have the SARS-CoV-2 virus and are infectious in the moment — even when you are showing no symptoms (asymptomatic).</p>
<figure class="align-center ">
<img alt="A hand dropping test solution onto a COVID-19 testing device." src="https://images.theconversation.com/files/435764/original/file-20211206-23-w66noa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435764/original/file-20211206-23-w66noa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435764/original/file-20211206-23-w66noa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435764/original/file-20211206-23-w66noa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435764/original/file-20211206-23-w66noa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435764/original/file-20211206-23-w66noa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435764/original/file-20211206-23-w66noa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">After mixing the nasal swab in the liquid solution, place the solution onto the test kit. Results will be ready in about 15 minutes.</span>
<span class="attribution"><span class="source">(Pixabay)</span></span>
</figcaption>
</figure>
<h2>3. How long before an event should I take a rapid test?</h2>
<p>A rapid test result is considered valid for the day you receive the results. So, it is most useful if you take the test shortly before you plan to attend an event or be in close quarters with others.</p>
<p>But you should be strategic about when you do it. For example, if you’re travelling four hours to see grandma for Christmas you likely want to take the test before you get in the car, because if you show up at grandma’s, take the test and find you’re positive, human nature might make you both want to bend the rules and have just a quick visit. </p>
<p>With the <a href="https://theconversation.com/will-omicron-the-new-coronavirus-variant-of-concern-be-more-contagious-than-delta-a-virus-evolution-expert-explains-what-researchers-know-and-what-they-dont-169020">infectiousness of the Delta variant and, possibly, Omicron</a>, this is not a safe choice.</p>
<p>If you have access to multiple tests and can test regularly — before you travel, before you interact with different groups of people on the same day — that is ideal.</p>
<h2>4. When should I not use it?</h2>
<p>Rapid tests should not be used when you are symptomatic and require a clinical diagnosis. Why? Because if you are symptomatic, you should self-isolate and/or get a PCR test, depending on <a href="https://www.canada.ca/en/public-health/services/diseases/2019-novel-coronavirus-infection/symptoms/provincial-territorial-resources-covid-19.html">your local guidelines</a> and your personal vaccine status.</p>
<p>Your symptoms might not be related to COVID-19. They could also be due to the influenza virus, which could still be harmful to pass on to the immunocompromised. If you’re feeling unwell, stay home and get a PCR test in accordance with your local guidelines. Period.</p>
<h2>5. How much does it cost? Where can I find one?</h2>
<p>In Canada, many small businesses have cropped up to provide rapid tests for travel with costs ranging from $75-130. But tests can also be purchased individually or by the box starting at $10 per test. </p>
<p>Publicly funded tests are harder to come by, and availability varies by jurisdiction. The <a href="https://www.canada.ca/en/public-health/services/diseases/2019-novel-coronavirus-infection/symptoms/testing/increased-supply.html">federal government</a> gave rapid tests to each province, but how these are being shared varies widely. </p>
<figure class="align-center ">
<img alt="Two COVID-19 test devices, one with a negative reading and one positive, against a black background" src="https://images.theconversation.com/files/435766/original/file-20211206-15-1chn159.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435766/original/file-20211206-15-1chn159.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=391&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435766/original/file-20211206-15-1chn159.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=391&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435766/original/file-20211206-15-1chn159.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=391&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435766/original/file-20211206-15-1chn159.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435766/original/file-20211206-15-1chn159.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435766/original/file-20211206-15-1chn159.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A negative rapid antigen test on the left and a positive test on the right.</span>
<span class="attribution"><span class="source">(Pixabay)</span></span>
</figcaption>
</figure>
<p>Pop-up rapid test distribution centres have emerged in B.C. communities with high rates of COVID-19 through the <a href="https://www.fraserhealth.ca/health-topics-a-to-z/coronavirus/testing/rapid-point-of-care-testing#.YaVTnlN6ppQ">Fraser Health Authority</a>. Saskatchewan has been distributing rapid tests through business-lobby groups and schools, but has found that many people <a href="https://www.cbc.ca/news/canada/saskatchewan/rapid-antigen-self-tests-saskatoon-1.6262224">don’t know how to use the tests correctly</a>. In Nova Scotia, infectious disease expert Dr. Lisa Barret has led a number of successful efforts to distribute rapid tests in the community, including <a href="https://www.cbc.ca/news/canada/nova-scotia/nova-scotia-covid-rapid-test-condom-packages-1.6196889">giving out condoms and COVID tests to university students</a>. </p>
<h2>The bottom line</h2>
<p>The best ways to protect yourself and your family from COVID-19 are to get vaccinated, wear a mask, keep your distance and gather outside when possible. If you choose to gather in person, rapid tests are one more tool in our toolbox to stay safe for the holidays. Remember, rapid tests aren’t for those with symptoms — they are only for people who are asymptomatic.</p><img src="https://counter.theconversation.com/content/172735/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kristen Haase receives funding from Health Canada and Roche to study rapid testing.</span></em></p><p class="fine-print"><em><span>Don D. Sin receives funding from Westjet/YVR to evaluate the feasibility of implementing rapid testing at airports. </span></em></p>Rapid testing for COVID-19 is an extra safety measure that can help prevent spread of infection, and help you have a more normal holiday, especially if you are visiting vulnerable people.Kristen Haase, Assistant Professor, Nursing, University of British ColumbiaDon D. Sin, Professor of Medicine, University of British ColumbiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1709172021-11-08T13:42:29Z2021-11-08T13:42:29ZWhat’s the difference between a PCR and antigen COVID-19 test? A molecular biologist explains<figure><img src="https://images.theconversation.com/files/430344/original/file-20211104-22364-c879nc.jpg?ixlib=rb-1.1.0&rect=160%2C171%2C6548%2C4295&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">All COVID-19 tests start with a sample, but the scientific process goes very differently after that.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/doctor-nurse-with-swab-test-sample-in-hospital-pcr-royalty-free-image/1296010648?adppopup=true"> Morsa Images/Digital Vision via Getty Images</a></span></figcaption></figure><p>At this point in the pandemic, you or someone you know has probably received at least one COVID-19 test. But do you know which kind of test you got and the strengths and weaknesses of these different tests?</p>
<p><a href="https://scholar.google.com/citations?user=OJ3tLoQAAAAJ&hl=en&oi=ao">I’m a molecular biologist</a>, and since April 2020 I’ve been part of a team <a href="https://www.nih.gov/research-training/medical-research-initiatives/radx">working on a National Institutes of Health-funded program called RADx</a> that is helping innovators develop rapid tests to detect when a person is infected with SARS-CoV-2, the virus that causes COVID-19. </p>
<p>Two major types of tests are used to diagnose infection with SARS-CoV-2: molecular tests – better known as <a href="https://www.fda.gov/consumers/consumer-updates/coronavirus-disease-2019-testing-basics">PCR tests</a> – and <a href="https://theconversation.com/antigen-tests-for-covid-19-are-fast-and-easy-and-could-solve-the-coronavirus-testing-problem-despite-being-somewhat-inaccurate-137977">antigen tests</a>. Each detects a different part of the virus, and how it works influences the test’s speed and relative accuracy. So what are the differences between these types of tests?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/430518/original/file-20211105-10546-1gy5rvp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A person in a white coat with gloves placing samples into a red laboratory device." src="https://images.theconversation.com/files/430518/original/file-20211105-10546-1gy5rvp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/430518/original/file-20211105-10546-1gy5rvp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430518/original/file-20211105-10546-1gy5rvp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430518/original/file-20211105-10546-1gy5rvp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430518/original/file-20211105-10546-1gy5rvp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430518/original/file-20211105-10546-1gy5rvp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430518/original/file-20211105-10546-1gy5rvp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">PCR tests are extremely accurate but require special lab equipment – like the PCR heating machine seen here – and can take hours or days to perform.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:PCR_masina_kasutamine.jpg#/media/File:PCR_masina_kasutamine.jpg">Karl Mumm via Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Looking for genetic evidence</h2>
<p>The first step for either kind of test is to get a sample from the patient. This can be a nasal swab or a bit of saliva. </p>
<p>For PCR tests, the next step is amplification of genetic material so that even a small amount of coronavirus genes in the patient’s sample can be detected. This is done using a technique called a <a href="https://www.genome.gov/about-genomics/fact-sheets/Polymerase-Chain-Reaction-Fact-Sheet">polymerase chain reaction</a>. A health care worker takes the sample and treats it with an enzyme that converts RNA into double-stranded DNA. Then, the DNA is mixed with a solution containing an enzyme called a polymerase and heated, causing the DNA to separate into two single-stranded DNA pieces. The temperature is lowered, and polymerase, with the help of a small piece of guide DNA called a primer, binds to the single-stranded DNA and copies it. The primers ensure that only coronavirus DNA is amplified. You’ve now created two copies of coronavirus DNA from the original one piece of RNA. </p>
<p>Laboratory machines <a href="https://www.jove.com/v/5056/pcr-the-polymerase-chain-reaction">repeat these heating and cooling cycles 30 to 40 times</a>, doubling the DNA until there are a <a href="https://www.thermofisher.com/us/en/home/life-science/cloning/cloning-learning-center/invitrogen-school-of-molecular-biology/pcr-education/pcr-reagents-enzymes/pcr-basics.html">billion copies of the original piece</a>. The amplified sequence contains fluorescent dye that is read by a machine. </p>
<p>The amplifying property of PCR allows the test to successfully detect even the smallest amount of coronavirus genetic material in a sample. This makes it a <a href="https://medlineplus.gov/lab-tests/pcr-tests/">highly sensitive and accurate test</a>. With <a href="https://www.finddx.org/covid-19/sarscov2-eval-molecular/">accuracy that approaches 100%</a>, it is the gold standard for diagnosing SARS–CoV–2.</p>
<p>However, PCR tests have some weaknesses too. They require a skilled laboratory technician and special equipment to run them, and the amplification process can take <a href="https://dx.doi.org/10.1016%2Fj.bdq.2017.05.002">an hour or more from start to finish</a>. Usually only large, centralized testing facilities – like hospital labs – can conduct many PCR tests at a time. Between sample collection, transportation, amplification, detection and reporting, it can take <a href="https://my.clevelandclinic.org/health/diagnostics/21462-covid-19-and-pcr-testing">from 12 hours to five days for a person to get results back</a>. And finally, they aren’t cheap at <a href="https://questdirect.questdiagnostics.com/products/covid-19-active-infection/">$100 or more per test</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/430526/original/file-20211105-10546-tm86ng.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two small white plastic tests with single lines showing negative tests results and a circular depression to place a sample." src="https://images.theconversation.com/files/430526/original/file-20211105-10546-tm86ng.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/430526/original/file-20211105-10546-tm86ng.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430526/original/file-20211105-10546-tm86ng.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430526/original/file-20211105-10546-tm86ng.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430526/original/file-20211105-10546-tm86ng.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430526/original/file-20211105-10546-tm86ng.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430526/original/file-20211105-10546-tm86ng.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Rapid antigen tests – like the two seen here showing negative results – are much faster and easier to perform but are less sensitive than PCR tests.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:COVID-19_rapid_test.jpg#/media/File:COVID-19_rapid_test.jpg">Lennardywlee via Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Antigen tests</h2>
<p><a href="https://theconversation.com/over-the-counter-rapid-antigen-tests-can-help-slow-the-spread-of-covid-19-heres-how-to-use-them-effectively-166869">Rapid, accurate tests are essential</a> to contain a highly contagious virus like SARS-CoV-2. PCR tests are accurate but can take a long time to produce results. Antigen tests, the other major type of coronavirus test, while much faster, are less accurate.</p>
<p>Antigens are substances that cause the body to produce an immune response – they trigger the generation of antibodies. These tests use lab-made antibodies to search for antigens from the SARS-CoV-2 virus.</p>
<p>To run an antigen test, you first treat a sample with a liquid containing salt and soap that breaks apart cells and other particles. Then you apply this liquid to a test strip that <a href="https://theconversation.com/antigen-tests-for-covid-19-are-fast-and-easy-and-could-solve-the-coronavirus-testing-problem-despite-being-somewhat-inaccurate-137977">has antibodies specific to SARS-CoV-2 painted on it in a thin line</a>. </p>
<p>Just like antibodies in your body, the ones on the test strip will <a href="https://labtestsonline.org/tests/covid-19-antigen-test">bind to any antigen in the sample</a>. If the antibodies bind to coronavirus antigens, a colored line appears on the test strip indicating the presence of SARS-CoV-2. </p>
<p>Antigen tests have a number of strengths. First, they are so easy to use that people with no special training can perform them and interpret the results – <a href="https://theconversation.com/rapid-screening-tests-that-prioritize-speed-over-accuracy-could-be-key-to-ending-the-coronavirus-pandemic-143882">even at home</a>. They also produce results quickly, <a href="https://theconversation.com/will-the-new-15-minute-covid-19-test-solve-us-testing-problems-145285">typically in less than 15 minutes</a>. Another benefit is that these tests can be relatively inexpensive at <a href="https://www.cvs.com/shop/home-health-care/home-tests/home-covid-test">around $10-$15 per test</a>. </p>
<p>Antigen tests do have some drawbacks. Depending on the situation, they can be <a href="https://doi.org/10.1093/infdis/jiab337">less accurate than PCR tests</a>. When a person is symptomatic or has a lot of virus in their system, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7799021/">antigen tests are very accurate</a>. However, unlike molecular PCR tests, antigen tests don’t amplify the thing they are looking for. This means there needs to be enough viral antigen in the sample for the antibodies on the test strip to generate a signal. When a person is in the early stages of infection, not a lot of virus is in the nose and throat, from which the samples are taken. So, antigen tests can <a href="https://doi.org/10.1038/d41586-021-00332-4">miss early cases of COVID-19</a>. It’s also <a href="https://www.cdc.gov/coronavirus/2019-ncov/faq.html#Symptoms-&-Emergency-Warning-Signs">during this stage that a person has no symptoms</a>, so they are more likely to be unaware they’re infected.</p>
<p>[<em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>.]</p>
<h2>More tests, better knowledge</h2>
<p>A few antigen tests are already available over the counter, and on Oct. 4, 2021, the Food and Drug Administration <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-additional-otc-home-test-increase-access-rapid-testing">granted emergency use authorization to another at-home antigen test</a>. The U.S. government is also pushing to <a href="https://www.hhs.gov/about/news/2021/10/25/new-hhs-actions-add-biden-administration-efforts-increase-access-easy-use-over-counter-covid-19-tests.html">make these tests more available to the public</a>. </p>
<p>At RADx, the project I am a part of, we are <a href="https://www.covid19testus.org/research-studies/test-us-at-home/">currently conducting clinical studies</a> to get a better understanding of how antigen tests perform at various stages of infection. The more data scientists have on how accuracy changes over time, the more effectively these tests can be used.</p>
<p>Understanding the strengths and limitations of both PCR and antigen tests, and when to use them, can help to bring the COVID-19 pandemic under control. So the next time you get a COVID-19 test, choose the one that is right for you.</p><img src="https://counter.theconversation.com/content/170917/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathaniel Hafer receives funding from the National Institutes of Health via awards UL1TR001453 and U54HL143541.</span></em></p>The two types of COVID-19 tests – antigen and PCR – work in very different ways, which is why one is fast but less accurate and the other is slow and precise.Nathaniel Hafer, Assistant Professor, Program in Molecular Medicine, UMass Chan Medical SchoolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1523042020-12-22T16:12:42Z2020-12-22T16:12:42ZEven though mass testing for COVID isn’t always accurate, it could still be useful – here’s why<p>The mass testing of asymptomatic people for COVID-19 in the UK was thrown into question by a recent study. In a pilot in Liverpool, <a href="https://www.bmj.com/content/371/bmj.m4848">over half the cases</a> weren’t picked up, leading some to question whether using tests that perform poorly is the best use of resources. </p>
<p>The tests involved in this study were antigen tests. These see whether someone is infected with SARS-CoV-2 by identifying structures on the outside of the virus, known as antigens, using antibodies. If the coronavirus is present in a sample, the antibodies in the test bind with the virus’s antigens and highlight an infection. </p>
<p>Antigen tests are cheap and provide results quickly. However, they are not always accurate. But what do we mean when we say that a test is inaccurate? And is it <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/878121/coronavirus-covid-19-testing-strategy.pdf">really the case</a> that “an unreliable test is worse than no test”?</p>
<h2>Sensitivity vs specificity</h2>
<p>When testing, one thing we’re interested in is how good a test is at detecting the virus in people who are actually infected. The more <em>sensitive</em> a test is, the less likely it is to deliver a false negative result to someone who has the virus.</p>
<p>False negatives can have significant costs. If people receiving them are also infectious, this may <a href="https://www.bmj.com/content/371/bmj.m4916">increase the risk</a> of viral transmission, as they’ll behave as if they don’t have the virus – what’s known as “false reassurance”.</p>
<p>But sensitivity is not the only kind of accuracy that matters – we’re also interested in how good the test is at providing positive results only to those who are actually infected. The more <em>specific</em> a test is, the less likely it is to deliver false positives to those without the virus. False positives also have costs – a person’s liberty might be restricted even though they pose no risk of transmission.</p>
<h2>The Liverpool data</h2>
<p><a href="https://www.gov.uk/government/publications/innova-lateral-flow-sars-cov-2-antigen-test-accuracy-in-liverpool-pilot-preliminary-data-26-november-2020">Preliminary data</a> from the Liverpool pilot suggests that the test used was 48.89% sensitive. That translates into a very high false negative rate, risking widespread false reassurance. The test cannot robustly confirm that someone isn’t infected.</p>
<p>However, there are other relevant points to consider from the Liverpool pilot. First, the study found that the specificity of the test was 99.93%. That means that only a small proportion of participants who weren’t infected were given a positive result by the test. This specificity is a good thing, but we shouldn’t overstate its importance; high specificity alone does not entail that a positive result is likely to be a true positive. This likelihood, or the test’s “positive predictive value”, is also partly determined by <a href="https://www.bmj.com/content/371/bmj.m4460">how prevalent the virus is</a> in the tested population. </p>
<p>For instance, say you test 100,000 people with a test that is 99.93% specific, yet the rate of COVID-19 in this group is relatively low – only 70 cases per 100,000 people. Among the 99,930 people who are uninfected, the test would still return a false positive result to 0.07% of them – roughly 70 people. So in this scenario, assuming the test is perfectly sensitive and picks up all the true positives, there would only be a 50% chance of a positive result being true.</p>
<p>Interestingly, the Liverpool data also suggests that the majority of true positive results were in individuals who had higher viral loads. If – and it is an <em>if</em> – higher viral loads are strongly associated with <a href="https://journals.plos.org/plosone/article/comments?id=10.1371/journal.pone.0243597">greater infectivity</a>, then these will be the <a href="https://www.nejm.org/doi/full/10.1056/NEJMp2025631">most important asymptomatic cases</a> to identify. </p>
<p>The upshot of this is that antigen testing has some features in its favour for identifying positive cases. The problem is that these benefits may be small if the virus is not prevalent, and they may be massively outweighed by the costs of false reassurance if it is widespread.</p>
<h2>Can we avoid false reassurance?</h2>
<p>There might be some measures that could potentially reduce these costs. The current messaging that increased testing can “<a href="https://www.bmj.com/content/370/bmj.m3558">provide reassurance</a>” amplifies the risk of false reassurance, but it could be changed. The advertised purpose of antigen testing could instead be to identify more of the asymptomatic carriers currently flying under the radar.</p>
<p>Some context is important here. In the UK, <a href="https://www.gov.uk/get-coronavirus-test">more accurate</a> testing is currently freely available only for symptomatic individuals and a small number of other groups. This strategy means that many asymptomatic carriers are being missed, and that’s a problem – <a href="https://www.acpjournals.org/doi/10.7326/M20-3012">approximately 40-45%</a> of infections are estimated to be asymptomatic.</p>
<p>It might also be possible to clarify to people that positive results are robust in a way that the negative results are not. We could also impose further restrictions on people with positive results without similarly using negative results as justification for releasing individuals from other existing restrictions. </p>
<p>One problem with all of these strategies is that they are difficult public health messages to communicate. However, the extent of the problem of false reassurance is also determined by the proportion of infectious people among the false negative cases. The Liverpool data suggests an avenue of further study here. </p>
<p>If we could establish firstly that people with low viral loads pose an acceptably low risk of transmission, and secondly that the false negatives generated by antigen tests were restricted to individuals with such low viral loads, then the harm of these false negatives would also be low. We currently lack crucial data to definitively establish these things. However, if we could, then it would support <a href="https://www.nejm.org/doi/full/10.1056/NEJMp2025631">the argument</a> that these tests could still be used as an effective containment strategy, based around highly frequent testing.</p>
<p>There are significant challenges for mitigating the harms of inaccurate mass antigen testing, and a number of <a href="https://blogs.bmj.com/bmj/2020/12/08/mike-gill-liverpools-pilot-of-mass-asymptomatic-testing-for-sars-cov-2-for-what-purpose-and-at-what-cost/">other questions</a> remain. But it’s still possible that some form of mass antigen testing could yet be useful in the future.</p><img src="https://counter.theconversation.com/content/152304/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Pugh currently receives funding from the UKRI, and has previously received funding from the Wellcome Trust</span></em></p>The pilot of mass testing people in Liverpool failed to pick up over half of cases, but this isn’t the end of the road for antigen testing.Jonathan Pugh, Research Fellow, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1522082020-12-17T19:54:50Z2020-12-17T19:54:50ZFDA authorized first over-the-counter COVID-19 test – useful but not a game changer<figure><img src="https://images.theconversation.com/files/375614/original/file-20201217-17-13f8w1f.png?ixlib=rb-1.1.0&rect=161%2C877%2C5344%2C3267&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The new rapid test is available without a prescription, but only 20 million are set to be sold by the middle of next year. </span> <span class="attribution"><a class="source" href="https://apnews.com/press-release/globenewswire-mobile/business-technology-pandemics-public-health-alabama-539d72db8cbf0f5666bcd58223a537a1">Ellume/AP</a></span></figcaption></figure><p>Soon, people in the U.S. will be able to pick up a <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-antigen-test-first-over-counter-fully-home-diagnostic">rapid antigen test</a> for COVID-19 from their local drugstore without a prescription, test themselves and process the results at home. </p>
<p>The Ellume COVID-19 Home Test that was granted an <a href="https://www.fda.gov/emergency-preparedness-and-response/mcm-legal-regulatory-and-policy-framework/emergency-use-authorization">emergency use authorization</a> from the Food and Drug Administration is expected <a href="https://www.nytimes.com/2020/12/15/health/rapid-covid-test-ellume.html">to cost US$30</a>, is easy to use and produces results within 20 minutes. </p>
<h2>How does the test work?</h2>
<p>The Ellume test is currently the most versatile rapid antigen test because it is authorized for testing anyone age 2 or over, <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-antigen-test-first-over-counter-fully-home-diagnostic">whether they have symptoms or not</a>. It is an antigen test that detects viral proteins, as opposed to the gold-standard PCR tests that detect viral genetic material.</p>
<p>The Ellume test includes a <a href="https://www.ellumehealth.com/2020/12/15/fda-authorizes-ellume-covid-19-home-test-as-first-over-the-counter-fully-at-home-diagnostic-test/">smartphone app</a> that provides step-by-step instructions explaining how to take a nasal swab and place it into the small analyzer that processes the sample. The app connects to the analyzer via Bluetooth to display the test results on the user’s phone. It is also possible to <a href="https://www.nytimes.com/2020/12/15/health/rapid-covid-test-ellume.html">transmit test results</a> securely and anonymously to public health authorities via the app, which helps provide data to guide COVID-19 policy decisions.</p>
<h2>How does the Ellume test compare to other rapid tests?</h2>
<p>Independent testing by the National Institutes of Health confirmed that the Ellume COVID-19 Home Test <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-antigen-test-first-over-counter-fully-home-diagnostic">successfully identified 96%</a> of PCR-confirmed COVID-19 positive cases in people with symptoms and <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-antigen-test-first-over-counter-fully-home-diagnostic">91% of PCR-confirmed cases</a> in <a href="https://theconversation.com/can-people-spread-the-coronavirus-if-they-dont-have-symptoms-5-questions-answered-about-asymptomatic-covid-19-140531">people without symptoms</a>. This is comparable to the <a href="https://theconversation.com/will-the-new-15-minute-covid-19-test-solve-us-testing-problems-145285">Abbott BinaxNOW rapid test</a>, another commonly used rapid antigen test, that reported agreement with PCR testing for 97.1% of COVID-19 positive cases with symptoms. </p>
<p>Health care providers have been using the <a href="https://theconversation.com/will-the-new-15-minute-covid-19-test-solve-us-testing-problems-145285">Abbott BinaxNOW</a> test for months, and it was <a href="https://www.forbes.com/sites/brucejapsen/2020/12/16/fda-clears-abbott-25-rapid-test-for-use-at-home/?sh=3748ab495210">also authorized for home use this week</a>. However, it is less versatile than the Ellume test since the Abbot test requires a prescription and is currently only authorized for home use in people within seven days of the onset of COVID-19 symptoms.</p>
<p>[<em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>.]</p>
<h2>How can this test be useful?</h2>
<p><a href="https://theconversation.com/rapid-screening-tests-that-prioritize-speed-over-accuracy-could-be-key-to-ending-the-coronavirus-pandemic-143882">Widespread rapid antigen testing</a> to slow COVID-19 transmission remains an important goal even though the FDA has already authorized a COVID-19 vaccine. At-home tests could boost testing rates by offering a quick and convenient alternative to testing at a doctor’s office or public testing site. Since the Ellume test is authorized for everyone, it should help identify COVID-19 cases in people without symptoms, which might otherwise go undetected.</p>
<h2>Are there enough tests to make a difference?</h2>
<p>Home-based antigen testing is one way to improve access to testing. While this test will help identify COVID-19 cases, the planned production of <a href="https://www.nytimes.com/2020/12/15/health/rapid-covid-test-ellume.html">20 million Ellume tests by mid-2021</a> still falls <a href="https://theconversation.com/rapid-covid-19-tests-can-be-useful-but-there-are-far-too-few-to-put-a-dent-in-the-pandemic-148429">far short of meeting the overall need</a> for testing in the U.S. to bring the pandemic under control. Some experts estimate that number could be as high as <a href="https://www.npr.org/sections/health-shots/2020/10/01/915793729/can-the-u-s-use-its-growing-supply-of-rapid-tests-to-stop-the-virus">14 million tests per day</a>.</p>
<p>Additionally, the $30 cost of the test poses a potential barrier to widespread and frequent use. Ideally, screening tests should <a href="https://theconversation.com/rapid-screening-tests-that-prioritize-speed-over-accuracy-could-be-key-to-ending-the-coronavirus-pandemic-143882">cost $1-$5 to achieve the high testing rates</a> needed to control the spread of the virus. Ultimately, the FDA may need to authorize more rapid screening tests if the U.S. is to meet the demand for testing.</p>
<p>Even though there <a href="https://theconversation.com/rapid-covid-19-tests-can-be-useful-but-there-are-far-too-few-to-put-a-dent-in-the-pandemic-148429">aren’t enough of these tests</a> to dramatically change the testing landscape, rapid testing can still help identify contagious cases early so infected people can avoid spreading the virus. This type of easy-to-use rapid antigen testing could also be used to screen travelers entering the U.S.</p>
<p>It will take months for the U.S. to reach the <a href="https://www.jhsph.edu/covid-19/articles/achieving-herd-immunity-with-covid19.html">vaccine-driven herd immunity threshold</a>. In the meantime, rising vaccination rates and rapid antigen testing can work together to slow transmission and suppress the virus. The Ellume test is not a game changer, but every little bit helps.</p><img src="https://counter.theconversation.com/content/152208/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Zoë McLaren does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A new over-the-counter COVID-19 test has been authorized by the FDA. Though it can be used to test people with and without symptoms, moderate cost and limited production mean it isn’t a game-changer.Zoë McLaren, Associate Professor of Public Policy, University of Maryland, Baltimore CountyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1484292020-12-01T13:24:23Z2020-12-01T13:24:23ZRapid COVID-19 tests can be useful – but there are far too few to put a dent in the pandemic<figure><img src="https://images.theconversation.com/files/372068/original/file-20201130-17-1elf41t.jpg?ixlib=rb-1.1.0&rect=254%2C0%2C3354%2C2223&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rapid tests for COVID-19 are easy to administer and give fast results. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/ExchangeCollaborativeTestingStrategy/cd621b49cd784744a268b9e648ecccdf/photo?Query=covid%20rapid%20test&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=463&currentItemNo=28">AP Photo/Julio Cortez, File</a></span></figcaption></figure><p>Since September, the Food and Drug Administration has <a href="https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/vitro-diagnostics-euas#individual-antigen">approved seven COVID-19 tests</a> that yield results in 30 minutes or less, offering hope for vast improvements in test access and efficiency throughout the U.S. Most of these are <a href="https://theconversation.com/antigen-tests-for-covid-19-are-fast-and-easy-and-could-solve-the-coronavirus-testing-problem-despite-being-somewhat-inaccurate-137977">antigen tests</a> that look for viral proteins and can be processed on portable machines or cards. </p>
<p>The idea behind these rapid tests is to detect symptomatic, pre-symptomatic and asymptomatic infectious people before they can spread the coronavirus. But despite massive distribution of these tests by federal officials – including <a href="https://www.hhs.gov/coronavirus/testing/rapid-test-distribution/index.html">to date over 40 million</a> of <a href="https://www.cbsnews.com/news/covid-rapid-test-abbott-labs-150-million/">150 million rapid tests ordered from the medical company Abbott</a> – COVID-19 transmission has been surging in every state since early November. </p>
<p>This calls into question whether the current influx of rapid tests can actually slow the spread of COVID-19. </p>
<p>In some targeted applications – and if people take other precautions including mask wearing and social distancing – rapid tests can be a valuable tool. But the current state of availability and accuracy of these tests greatly limit how effective they are at slowing the spread of the virus in communities.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/372069/original/file-20201130-13-1q24h4i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A healthcare worker placing a sample into a the small Abbott ID Now processing machine." src="https://images.theconversation.com/files/372069/original/file-20201130-13-1q24h4i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/372069/original/file-20201130-13-1q24h4i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/372069/original/file-20201130-13-1q24h4i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/372069/original/file-20201130-13-1q24h4i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/372069/original/file-20201130-13-1q24h4i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/372069/original/file-20201130-13-1q24h4i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/372069/original/file-20201130-13-1q24h4i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Rapid tests like the Abbott ID Now require only small, portable machines and can give results in 15 minutes, but they sacrifice accuracy.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakCalifornia/2b7302f66ad440708223cfdb75dc12e9/photo?Query=covid%20rapid%20test&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=463&currentItemNo=53">AP Photo/Jeff Chiu</a></span>
</figcaption>
</figure>
<h2>Speed over accuracy</h2>
<p>Rapid antigen tests are an attractive option because in addition to their speed, they are <a href="https://theconversation.com/rapid-screening-tests-that-prioritize-speed-over-accuracy-could-be-key-to-ending-the-coronavirus-pandemic-143882">cheap and easy to produce</a> and therefore more broadly available than the <a href="https://theconversation.com/how-does-the-coronavirus-test-work-5-questions-answered-133118">more commonly used gold-standard PCR tests</a> in theory. But these attributes come with a trade-off: <a href="https://www.theatlantic.com/health/archive/2020/10/do-rapid-antigen-tests-have-accuracy-problem/616681/">less diagnostic accuracy</a>. This makes them an excellent candidate for <a href="https://theconversation.com/will-the-new-15-minute-covid-19-test-solve-us-testing-problems-145285">use as a screening tool</a>, though less useful for accurately diagnosing SARS-CoV-2 infection. </p>
<p>One-time testing does not mean that a person can <a href="https://www.nytimes.com/2020/11/21/upshot/coronavirus-test-thanksgiving-plans.html">safely travel or mingle without precautions</a>. And while no test is perfectly accurate, there are real questions about the performance of the new rapid tests. </p>
<p>A few test manufacturers <a href="https://www.quidel.com/sites/default/files/product/documents/EF1438903EN00.pdf">reported accuracy</a> between 84.0% and 97.6% in individuals who are tested within five days after developing COVID-19 symptoms. There is, however, an apparent gap between the reported performance of these tests and <a href="https://www.nytimes.com/2020/11/02/health/coronavirus-testing-quidel-sofia.html">what is achieved in the real world</a>. Anecdotally, these tests seem to <a href="https://www.nytimes.com/2020/11/02/health/coronavirus-testing-quidel-sofia.html">miss recent, mild and asymptomatic infections</a> – in fact, rapid tests are authorized by the U.S. Centers for Disease Control and Prevention only for <a href="https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html">use in symptomatic COVID-19 patients</a>. And of course, people can still be infected soon after getting tested. </p>
<p>For rapid tests to effectively limit spread of the coronavirus, experts suggest that they must be <a href="http://doi.org/10.1001/jamanetworkopen.2020.16818">conducted with high frequency</a> – you might miss some cases, but if everyone were getting tested all the time, you would catch a lot of cases too. But even frequent testing is not a panacea. It’s only one part of an approach that must also include social distancing, mask wearing and other precautions.</p>
<p>A highly publicized example of how a rapid testing strategy can go wrong occurred when President Trump and many in his inner circle contracted COVID-19, likely stemming from a single superspreading event. Everyone was reportedly getting daily rapid tests, but they were largely ignoring other measures like face masks and social distancing. It is likely that someone was <a href="https://www.technologyreview.com/2020/10/07/1009636/rapid-covid-tests-can-work-white-houses-mistakes-trump-abbott/">infected and asymptomatic, tested negative, and then started the outbreak</a>. </p>
<h2>Widespread, repeat testing</h2>
<p>Detecting pre-symptomatic and asymptomatic individuals who are infectious is critical to controlling the coronavirus. <a href="https://dx.doi.org/10.1101%2F2020.06.22.20136309">Rapid tests can do this</a>, but only if people are screened repeatedly on a schedule – much as what has been <a href="https://www.bostonglobe.com/2020/11/02/sports/with-careful-planning-total-commitment-nba-constructed-safest-place-earth/">happening in some professional</a> and intercollegiate sports. </p>
<p>The idea is that by testing people early and often – perhaps even <a href="https://www.nytimes.com/2020/07/03/opinion/coronavirus-tests.html">as much as every day</a> – rapid tests <a href="https://theconversation.com/will-the-new-15-minute-covid-19-test-solve-us-testing-problems-145285">can catch infected people before they spread the coronavirus to others</a>. But on a national scale, that is a huge number of tests.</p>
<p>Researchers have estimated that the U.S. would need to perform at least 20 million rapid tests per day to <a href="https://www.rapidtests.org/">drive down infections</a>. The 150 million rapid tests ordered by the government in late August were earmarked for high-risk populations, but would barely cover one week for the population at large. And don’t forget that logistic capabilities, compliance to frequent testing and the infrastructure to act quickly on results all need to happen as well.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/372071/original/file-20201130-17-b1ufyk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A healthcare worker administering a rapid test to an elderly man." src="https://images.theconversation.com/files/372071/original/file-20201130-17-b1ufyk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/372071/original/file-20201130-17-b1ufyk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/372071/original/file-20201130-17-b1ufyk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/372071/original/file-20201130-17-b1ufyk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/372071/original/file-20201130-17-b1ufyk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/372071/original/file-20201130-17-b1ufyk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/372071/original/file-20201130-17-b1ufyk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Nursing homes were some of the first places to receive rapid tests.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakNursingHomeTesting/92040888c49f470bac9c060c1a90a047/photo?Query=nursing%20home%20covid&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=617&currentItemNo=33">AP Photo/Ted S. Warren</a></span>
</figcaption>
</figure>
<h2>A targeted approach</h2>
<p>There simply aren’t enough rapid tests being produced for the general public to get repeat testing, so the federal government has <a href="https://www.kff.org/coronavirus-covid-19/issue-brief/state-reporting-of-cases-and-deaths-due-to-covid-19-in-long-term-care-facilities/">prioritized deployment of rapid tests to the high-risk population of nursing homes</a>. Federal guidelines for rapid test use in long-term care facilities are a great example of what a testing program might look like – but also illustrate the <a href="https://www.nytimes.com/2020/10/07/health/nevada-covid-testing-nursing-homes.html">current challenges in the use of rapid tests</a>.</p>
<p>If even one person in a nursing home tests positive, all staff and residents must be <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/nursing-homes-antigen-testing.html">tested every three to seven days</a> until the facility has been free of COVID–19 for 14 days. When a facility has no cases, all staff are required to get tested <a href="https://www.cdc.gov/coronavirus/2019-ncov/downloads/hcp/nursing-home-testing-algorithm-508.pdf">according to their county’s test-positivity rate</a> – the <a href="https://www.cms.gov/files/document/qso-20-38-nh.pdf">higher the rate, the more testing is needed</a>.</p>
<p>[<em>The Conversation’s science, health and technology editors pick their favorite stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-favorite">Weekly on Wednesdays</a>.]</p>
<p>Yet nursing homes have had problems with <a href="https://www.nytimes.com/2020/09/29/health/covid-nursing-homes-testing.html">accuracy, staffing and costs</a> while using these tests and find themselves <a href="https://khn.org/news/article/nursing-homes-still-see-dangerously-long-waits-for-covid-test-results/">again in crisis during the current surge</a>. While the rapid tests certainly helped catch many cases and should be used in these settings, they cannot single-handedly overcome <a href="https://www.npr.org/sections/health-shots/2020/10/26/927841874/they-work-in-several-nursing-homes-to-eke-out-a-living-and-that-spreads-the-virus">larger issues that contribute to spread in these settings</a>. </p>
<p>Rapid tests can be effective in highly controlled settings where people are tested frequently and other mitigation measures are in place. Look to the <a href="https://www.latimes.com/science/newsletter/2020-10-12/coronavirus-today-nba-bubble-success-covid-lakers-coronavirus-today">success of the NBA bubble</a> as proof. But in other settings where isolation, mask wearing and social distancing are hard to implement or not followed – like nursing homes or the White House – rapid tests have not kept the virus at bay. </p>
<p>Current testing capacity is nowhere near the hundreds of millions of tests per week required to protect the general population. To date, the promise of cheap and convenient COVID-19 tests being the sole means of controlling disease transmission has not been realized.</p><img src="https://counter.theconversation.com/content/148429/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr. Bonnie LaFleur receives funding from NIH, NCI, NIA. She is affiliated with Cofactor Genomics as a consultant. </span></em></p><p class="fine-print"><em><span><a href="mailto:kellingson@arizona.edu">kellingson@arizona.edu</a> receives funding from Centers for Disease Control and Prevention, Arizona Biomedical Research Commission, Arizona Area Health Education Centers, National Association for City and County Health Officials. </span></em></p>In September, production of rapid tests really ramped up in the US. But due to low accuracy and massive numbers needed, these tests alone are unlikely to have much of an effect on the pandemic.Bonnie LaFleur, Professor of Biostatistics, University of ArizonaKatherine Ellingson, Assistant Professor of Epidemiology and Biostatistics, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1471542020-10-23T12:23:10Z2020-10-23T12:23:10ZHow to use COVID-19 testing and quarantining to safely travel for the holidays<figure><img src="https://images.theconversation.com/files/364823/original/file-20201021-15-l4nww4.jpg?ixlib=rb-1.1.0&rect=128%2C98%2C4907%2C3238&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">For anyone thinking about traveling during the pandemic, COVID-19 testing can be an important, but not all-powerful, tool. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakMemorialDayTravel/1766cbc5f60b4d94ba5c484b49591712/photo?Query=COVID%20airport%20family&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=13&currentItemNo=11">AP Photo/Charlie Riedel</a></span></figcaption></figure><p>With the holidays approaching, many people are considering whether to visit relatives or friends in the coming weeks. At the same time, cases of COVID-19 are surging toward the highest levels since the beginning of the pandemic. As <a href="https://chmfamilymedicine.msu.edu/people/claudia-finkelstein/">a physician</a>, daughter of vulnerable seniors and mother of young adults, I have been thinking a lot about whether testing will help me decide if it’s safe to see my family. </p>
<p>Testing may help you to make sure you and your loved ones stay healthy, but COVID-19 testing is not as simple as yes or no, infected or safe. There are many factors to keep in mind when using a coronavirus test to plan your holiday travels safely.</p>
<h2>Some tests are better than others</h2>
<p>Broadly speaking, there are two categories of tests. </p>
<p><a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/testing-overview.html">Antibody tests</a> – which look for evidence of previous infection – can’t tell you whether you currently have COVID-19 and aren’t useful for planning to visit family.</p>
<p>The other category of tests look for evidence of the <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/testing-overview.html">virus in your body</a>. There are two types of these viral tests available – <a href="https://www.cdc.gov/coronavirus/2019-ncov/lab/testing.html">RT–PCR tests</a> and <a href="https://theconversation.com/antigen-tests-for-covid-19-are-fast-and-easy-and-could-solve-the-coronavirus-testing-problem-despite-being-somewhat-inaccurate-137977">rapid antigen tests</a> – and these are the ones to use when trying to prevent the spread of the coronavirus.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/364825/original/file-20201021-13-1uxg0t0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A medical professional inserting a nasal swab into an older man's nose." src="https://images.theconversation.com/files/364825/original/file-20201021-13-1uxg0t0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/364825/original/file-20201021-13-1uxg0t0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364825/original/file-20201021-13-1uxg0t0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364825/original/file-20201021-13-1uxg0t0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364825/original/file-20201021-13-1uxg0t0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364825/original/file-20201021-13-1uxg0t0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364825/original/file-20201021-13-1uxg0t0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The gold standard viral test is an RT–PCR test that looks for viral genetic material.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakVaccineDiversity/c85cfe10d1aa46658a8d072beeda56bb/photo?Query=COVID%20testing%20swab&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=1125&currentItemNo=7">AP Photo/Taimy Alvarez</a></span>
</figcaption>
</figure>
<p>No lab test for COVID-19 is 100% accurate. Although false positives are certainly not a good thing, a false negative result – testing negative when you actually have the virus – is the bigger danger if you plan on seeing family. The false negative rates for RT-PCR tests <a href="https://doi.org/10.1136/bmj.m1808">range from 2%-29%</a>. Much of that range is due to different manufacturers and user error. While fairly accurate, these tests often involve a visit to a health care provider and are somewhat expensive – <a href="https://www.cnn.com/2020/07/15/health/coronavirus-test-cost/index.html">around US$100</a>, though <a href="https://www.castlighthealth.com/wp-content/uploads/2020/03/Costs-of-COVID-19.pdf">costs vary widely by state</a> – and it can take <a href="https://www.kateto.net/covid19/COVID19%20CONSORTIUM%20REPORT%2017%20TEST%20OCT%202020.pdf">up to three days to get results</a>. RT-PCR tests are the best tests available, but for some people, especially if you’ll be seeing someone in a vulnerable age group, the high-end 29% false negative rate might leave more uncertainty than you are comfortable with. </p>
<p>Rapid antigen tests, in comparison, are <a href="https://www.sciencemag.org/news/2020/08/milestone-fda-oks-simple-accurate-coronavirus-test-could-cost-just-5">faster and cheaper</a>, but less accurate than RT–PCR tests. You can usually get results within a day of taking the test, but false negative rates can be <a href="https://www.sciencemag.org/news/2020/05/coronavirus-antigen-tests-quick-and-cheap-too-often-wrong">as high as 50%</a>. They are most likely to be accurate when they are <a href="https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html">given to people with symptoms</a> within a week of symptom onset, but rapid tests are not meant to be diagnostic tests for an individual. They are much better at <a href="https://theconversation.com/rapid-screening-tests-that-prioritize-speed-over-accuracy-could-be-key-to-ending-the-coronavirus-pandemic-143882">monitoring whole populations where people can be tested repeatedly</a>, and quite frankly have little use as a one-time test.</p>
<p>With a rapid test you may get results instantaneously at a lower price, but they should not be the only thing to inform a travel decision. When the health of a family member is on the line, accuracy is your friend. RT–PCR tests are generally considered to be more accurate.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364826/original/file-20201021-17-b8xxrj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Crowds of people walking on sidewalks in Las Vegas, some wearing masks, some not." src="https://images.theconversation.com/files/364826/original/file-20201021-17-b8xxrj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364826/original/file-20201021-17-b8xxrj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364826/original/file-20201021-17-b8xxrj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364826/original/file-20201021-17-b8xxrj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364826/original/file-20201021-17-b8xxrj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364826/original/file-20201021-17-b8xxrj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364826/original/file-20201021-17-b8xxrj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Any potential exposure, like walking in a crowded area or being in an enclosed indoor space, can reset the 14-day quarantine period.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreak-Nevada/58804eaa0ab34c3da4482b26c3800060/photo?Query=crowd%20covid%20mask&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=38&currentItemNo=13">AP Photo/John Locher,File</a></span>
</figcaption>
</figure>
<h2>Timing matters</h2>
<p>Regardless of which viral test you use, the results are accurate only for the moment when you were tested and reflect only the ability of the test to detect the virus. A negative result today of course doesn’t prevent you from getting infected tomorrow.</p>
<p>But with the coronavirus, neither does a negative test mean you haven’t been exposed to the virus. The time between coming in contact with the virus and beginning to shed infectious virus particles – the incubation period – varies anywhere <a href="https://www.health.harvard.edu/diseases-and-conditions/if-youve-been-exposed-to-the-coronavirus#:%7E:text=The%20time%20from%20exposure%20to,before%20starting%20to%20experience%20symptoms">between two and 14 days</a>. For example, it’s possible you could get exposed today, test negative tomorrow and then go on to be infectious a few days later.</p>
<p>Additionally, it is possible to <a href="https://doi.org/10.1073/pnas.2008373117">spread the virus before you show symptoms</a> – when you are presymptomatic – or even if you <a href="https://theconversation.com/can-people-spread-the-coronavirus-if-they-dont-have-symptoms-5-questions-answered-about-asymptomatic-covid-19-140531">never develop any symptoms at all</a>. </p>
<h2>Minimize risk, accept uncertainty</h2>
<p>First off, if you have any symptoms at all, stay home. If you do not have symptoms, then you can start to think about travel for the holidays.</p>
<p>Knowing that tests are imperfect, the safest thing you can do is to <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/duration-isolation.html">strictly self-quarantine for 14 days before your visit</a>. Testing can offer a helpful data point, but a quarantine is the more foolproof option.</p>
<p>If you can’t quarantine for a full 14 days, the next best thing is to limit potential exposure to the virus, isolate as much as possible as long as possible before you travel and get tested.</p>
<p>If you are worried about being an asymptomatic carrier and are unable to isolate, consider getting tested at least five days after your last possible exposure. This <a href="https://www.aamc.org/news-insights/your-covid-19-testing-questions-answered">maximizes the chance of a test detecting the virus</a> if you are infected. </p>
<p>Remember that traveling itself carries risk of exposure too. Driving with appropriate precautions – wear a mask, wash your hands and social distance – seems to be <a href="https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-safe-travel-advice/art-20486965">safer than flying</a>.</p>
<p>The process of flying – the crowded airports, bus rides and close seating on the plane – is a <a href="https://wwwnc.cdc.gov/eid/article/26/11/20-3299_article">serious exposure risk</a>. Ideally, after flying you would self–isolate again at your destination for as long as possible and consider getting tested. That is a lot of time alone and waiting for test results, but I can think of no higher stakes than the safety of loved ones.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/365066/original/file-20201022-16-vlsda9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A flowchart from the CDC showing when to delay travel." src="https://images.theconversation.com/files/365066/original/file-20201022-16-vlsda9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/365066/original/file-20201022-16-vlsda9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=776&fit=crop&dpr=1 600w, https://images.theconversation.com/files/365066/original/file-20201022-16-vlsda9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=776&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/365066/original/file-20201022-16-vlsda9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=776&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/365066/original/file-20201022-16-vlsda9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=976&fit=crop&dpr=1 754w, https://images.theconversation.com/files/365066/original/file-20201022-16-vlsda9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=976&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/365066/original/file-20201022-16-vlsda9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=976&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There are a lot of reasons to delay travel, and during a pandemic, caution is wise.</span>
<span class="attribution"><a class="source" href="https://www.cdc.gov/coronavirus/2019-ncov/travelers/when-to-delay-travel.html">Centers for Disease Control</a></span>
</figcaption>
</figure>
<h2>You’re not in it alone</h2>
<p>Maintaining health is a group effort, and it takes only one infected person to cause an outbreak. Openly discuss the precautions that the people you are visiting are taking and the possibilities of social distancing during the visit. </p>
<p>[<em>Get facts about coronavirus and the latest research.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=coronavirus-facts">Sign up for The Conversation’s newsletter.</a>]</p>
<p>Remember that one negative test in a party of travelers is only that, one negative test. Just because you test negative doesn’t mean you can assume that other people in your household are negative too. Everyone needs to get tested and follow the same isolation measures, as much of the spread occurring <a href="https://www.cnn.com/2020/10/14/health/us-coronavirus-wednesday/index.html">is happening at smaller private gatherings in close quarters</a>.</p>
<p>Many people want to see our loved ones during the holidays. But there are enormous, life-and-death reasons to plan the visit carefully and to use information, isolation and testing wisely. You may decide that the risk is too high, and that is OK. But, if you decide to visit for the holidays, the safest option is a strict 14-day quarantine. Testing can help inform your decision, but is not the only thing that you should rely on.</p><img src="https://counter.theconversation.com/content/147154/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Claudia Finkelstein does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Over the approaching holidays, people around the world will want to travel to see friends and family. Getting tested for the coronavirus can make this safer, but testing alone is not a perfect answer.Claudia Finkelstein, Associate Professor of Family Medicine, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1468442020-09-25T07:36:02Z2020-09-25T07:36:02ZThe new 15-minute test has potential, but standard tests are still the best way to track COVID-19<p>Testing remains a vital component of Australia’s success in managing COVID-19. </p>
<p>We need to diagnose people infected with SARS-CoV-2, the virus that causes COVID-19, as early as possible so they can be isolated from others and their contacts quarantined. Testing also helps us understand to what degree the virus is present in the population, so we can tailor public health measures accordingly.</p>
<p>If you’ve had a COVID-19 test, in all likelihood you received a PCR test. That’s the one with the throat and nose swabs, and is regarded as the “gold standard” in COVID-19 testing.</p>
<p>But now the Therapeutic Goods Administration (TGA) has approved <a href="https://www.theguardian.com/australia-news/2020/sep/24/australias-drug-regulator-tga-approves-covid-tests-that-deliver-results-in-15-minutes">a new kind of COVID-19 test</a>, which can produce results in as little as 15 minutes, as opposed to a day or more for standard tests. </p>
<p>So is this new rapid test set to revolutionise COVID-19 testing in Australia? Not quite yet.</p>
<h2>The traditional tests</h2>
<p>Nucleic acid tests, or PCR tests, can detect ribonucleic acid (RNA) of SARS-CoV-2 from a day or two before symptoms start, and for a week or more afterwards, as symptoms resolve. Of course, some people will test positive without ever having symptoms.</p>
<p>PCR tests have been the backbone of SARS-CoV-2 testing worldwide. Because of the vast global experience with PCR tests and their high performance, they’re considered <a href="https://www.health.gov.au/resources/publications/phln-guidance-on-laboratory-testing-for-sars-cov-2-the-virus-that-causes-covid-19">the most reliable</a> COVID-19 test.</p>
<p>PCR tests require specialised laboratory equipment and trained scientists and technicians to test the specimens; processing and testing take several hours.</p>
<p>Since January, we’ve performed an astonishing <a href="https://www.health.gov.au/sites/default/files/documents/2020/09/coronavirus-covid-19-at-a-glance-23-september-2020.pdf">7.4 million</a> SARS-CoV-2 PCR tests in Australia, which has needed a massive upscaling of capacity in laboratories nationally. </p>
<figure class="align-center ">
<img alt="An illustration of SARS-CoV-2, the coronavirus that causes COVID-19." src="https://images.theconversation.com/files/359948/original/file-20200925-20-1g0i3oy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359948/original/file-20200925-20-1g0i3oy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=382&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359948/original/file-20200925-20-1g0i3oy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=382&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359948/original/file-20200925-20-1g0i3oy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=382&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359948/original/file-20200925-20-1g0i3oy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=480&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359948/original/file-20200925-20-1g0i3oy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=480&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359948/original/file-20200925-20-1g0i3oy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=480&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">PCR tests detect SARS-CoV-2 viral RNA.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>At times, demand for PCR testing has exceeded capacity, occasionally resulting in delays of <a href="https://theconversation.com/got-a-covid-19-test-in-victoria-and-still-havent-got-your-results-heres-what-may-be-happening-and-what-to-do-142821">up to several days</a> in getting results back to patients. Meanwhile, laboratories swamped with COVID-19 tests may be limited in their capacity to perform their routine business, including diagnostic testing for other infectious diseases.</p>
<p>As people are required to isolate until they <a href="https://www.health.gov.au/news/health-alerts/novel-coronavirus-2019-ncov-health-alert/what-you-need-to-know-about-coronavirus-covid-19#testing">receive a negative test result</a> and their symptoms resolve, these delays may come at a cost to the person waiting, their family, and the economy.</p>
<p>Recognising these costs may lead some people to choose not to be tested, Victoria has offered <a href="https://www.dhhs.vic.gov.au/covid-19-worker-support-payment">financial compensation</a> for people without leave entitlements awaiting test results. </p>
<p>But delayed case confirmation also increases the time to identification and quarantine of contacts, undermining public health efforts. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australias-coronavirus-testing-rates-are-some-of-the-best-in-the-world-compare-our-stats-using-this-interactive-142289">Australia's coronavirus testing rates are some of the best in the world – compare our stats using this interactive</a>
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</em>
</p>
<hr>
<h2>What can we expect from the antigen test?</h2>
<p>Rapid antigen tests can diagnose COVID-19 <a href="https://www.theage.com.au/national/victoria/15-minutes-to-diagnosis-the-quick-covid-test-that-could-change-the-game-20200923-p55yk1.html">in 15 minutes</a>. They’re relatively inexpensive and require a swab from the nose.</p>
<p>These tests detect viral antigens, proteins on the surface of SARS-CoV-2. The immune system recognises these proteins as foreign, and responds by making antibodies to SARS-CoV-2 (“<a href="https://theconversation.com/antigen-tests-for-covid-19-are-fast-and-easy-and-could-solve-the-coronavirus-testing-problem-despite-being-somewhat-inaccurate-137977">anti-gen</a>” means antibody generator). </p>
<p>Antigen tests perform best early in the infection when the amount of virus in a person’s system is highest. For a person with symptomatic COVID-19, this would be in the first week of symptoms. So they only pick up current infections – <a href="https://www.tga.gov.au/covid-19-testing-australia-information-health-professionals">unlike antibody tests</a>, which can detect if a person was previously infected with SARS-CoV-2.</p>
<p>Four SARS-CoV-2 rapid antigen tests have been <a href="https://www.tga.gov.au/covid-19-test-kits-included-artg-legal-supply-australia">licensed for use</a> in Australia in the past two months.</p>
<p>Unfortunately, rapid antigen tests for COVID-19 appear to be less sensitive than PCR tests, meaning they may give a negative result in someone who does actually have COVID-19. One of the recently licensed rapid antigen tests may give a false negative result in <a href="https://www.finddx.org/wp-content/uploads/2020/09/Bionote_Ag-INTERIM-Public-Report_20200918.pdf">up to 18.3%</a> of people with COVID-19 diagnosed by PCR.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-whats-the-new-coronavirus-saliva-test-and-how-does-it-work-141877">Explainer: what's the new coronavirus saliva test, and how does it work?</a>
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</em>
</p>
<hr>
<p>While a positive rapid antigen test result is more reliable, widespread use of these tests in asymptomatic people will result in some <a href="https://theconversation.com/the-positives-and-negatives-of-mass-testing-for-coronavirus-137792">false positive</a> results — that is, a positive test result in someone who doesn’t have COVID-19.</p>
<p>At this stage, <a href="https://www1.health.gov.au/internet/main/publishing.nsf/Content/cdna-song-novel-coronavirus.htm">national COVID-19 guidelines</a> don’t include information on antigen tests. So a person with a positive antigen test would need to undergo a PCR test to be counted in Australia’s official COVID-19 case numbers.</p>
<h2>Considering the pros and cons</h2>
<p>We’re faced with a trade-off between the potential benefits of the rapid antigen tests — the ability to test larger numbers of people, consuming fewer laboratory resources, and quicker results — and the potential to miss a few cases because of the lower test sensitivity.</p>
<p>Despite the lower sensitivity, increasing testing rates might result in an overall net increase in the proportion of COVID-19 cases diagnosed, and therefore a <a href="https://www.medrxiv.org/content/10.1101/2020.06.22.20136309v3">public health benefit</a> by preventing onward transmission from these cases.</p>
<p>One possible strategic use of these tests may be in screening people without symptoms to detect asymptomatic and pre-symptomatic infection that might otherwise go undetected. This <a href="https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html">could include</a> people in workplaces where ongoing exposure to colleagues and the public is unavoidable, including sectors of the food supply chain or other essential services.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-cant-we-use-antibody-tests-for-diagnosing-covid-19-yet-138519">Why can't we use antibody tests for diagnosing COVID-19 yet?</a>
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</em>
</p>
<hr>
<p>Because of the lower test sensitivity for the rapid antigen test, a PCR test remains most appropriate for people with symptoms, those at greater risk of poor outcomes from COVID-19, and people working in high-risk settings like aged care and health care.</p>
<p>While rapid antigen tests show promise, we’ll need to evaluate their efficacy in Australia before we can determine their role in our fight against COVID-19.</p><img src="https://counter.theconversation.com/content/146844/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katherine Gibney receives funding from the NHMRC / MRFF, the University of Melbourne, MCRI, the Royal Australasian College of Physicians, and the Isabel & John Gilbertson Charitable Trust. </span></em></p><p class="fine-print"><em><span>Deborah Williamson receives funding from the National Health and Medical Research Council.</span></em></p><p class="fine-print"><em><span>Jodie McVernon receives funding from The Australian Government Department of Health Office of Health Protection, The Australian Government Department of Foreign Affairs and Trade Indo-Pacific Centre for Health Security and the National Health and Medical Research Council</span></em></p>A new test, which can diagnose COVID-19 in 15 minutes, has been approved by the TGA. But it’s no silver bullet.Katherine Gibney, NHMRC early career fellow, The Peter Doherty Institute for Infection and ImmunityDeborah Williamson, Professor of Microbiology, The Peter Doherty Institute for Infection and ImmunityJodie McVernon, Professor and Director of Doherty Epidemiology, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1452852020-09-01T12:39:29Z2020-09-01T12:39:29ZWill the new 15-minute COVID-19 test solve US testing problems?<figure><img src="https://images.theconversation.com/files/355644/original/file-20200831-22-1tkm5yq.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4912%2C3551&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Easy, fast coronavirus testing is critical to controlling the virus.</span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Virus-Outbreak-Washington/079818634ad24a938d8488056c56be83/35/0">AP Photo/Elaine Thompson</a></span></figcaption></figure><p>On Aug. 26, the <a href="https://www.fda.gov/home">Food and Drug Administration</a> granted an <a href="https://www.fda.gov/media/141567/download">Emergency Use Authorization</a> to a new rapid <a href="https://theconversation.com/antigen-tests-for-covid-19-are-fast-and-easy-and-could-solve-the-coronavirus-testing-problem-despite-being-somewhat-inaccurate-137977">antigen test</a> for COVID-19 called the <a href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">BinaxNOW test</a>.</p>
<p>I <a href="https://scholar.google.com/citations?hl=en&user=t6ZtGJwAAAAJ">study public health policy</a> to combat infectious disease epidemics. Testing is one of the most powerful tools available to fight the spread of COVID-19. The new test is <a href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">inexpensive, rapid and easy to use</a>. It will <a href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">massively scale up</a> access to testing, but hurdles remain in achieving widespread, frequent COVID-19 testing.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/355579/original/file-20200831-21-vfnu2i.jpeg?ixlib=rb-1.1.0&rect=60%2C80%2C1226%2C916&q=45&auto=format&w=1000&fit=clip"><img alt="A digital results page for the BinaxNOW test." src="https://images.theconversation.com/files/355579/original/file-20200831-21-vfnu2i.jpeg?ixlib=rb-1.1.0&rect=60%2C80%2C1226%2C916&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/355579/original/file-20200831-21-vfnu2i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/355579/original/file-20200831-21-vfnu2i.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/355579/original/file-20200831-21-vfnu2i.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/355579/original/file-20200831-21-vfnu2i.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/355579/original/file-20200831-21-vfnu2i.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/355579/original/file-20200831-21-vfnu2i.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Abbott BinaxNOW rapid antigen test claims to give results in 15 minutes.</span>
<span class="attribution"><a class="source" href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">Abbott</a></span>
</figcaption>
</figure>
<h2>What type of test is BinaxNOW?</h2>
<p>The credit-card-sized test is an antigen test that detects a <a href="https://blogs.sciencemag.org/pipeline/archives/2020/08/27/thoughts-on-a-new-coronavirus-test-and-on-testing">specific viral protein</a> from SARS-CoV-2. It <a href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">costs US$5</a> and doesn’t require a lab or a machine for processing. </p>
<p>Performing the test is simple. A health care worker or technician would use a swab to collect a sample from <a href="https://www.fda.gov/media/141570/download">less than 1 inch inside the nostril</a>. They would then combine the sample with a <a href="https://www.fda.gov/media/141570/download">few drops of chemicals</a> inside the test card. Within 15 minutes, the test strip would show a positive or negative result. The <a href="https://www.abbott.com/BinaxNOW-Test-NAVICA-App.html">test is also paired with an app</a> that produces a digital code that can be scanned to show proof of a recent negative COVID-19 test.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/355586/original/file-20200831-18-x9b4ak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sign showing the FDA logo with the FDA headquarters in the background." src="https://images.theconversation.com/files/355586/original/file-20200831-18-x9b4ak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/355586/original/file-20200831-18-x9b4ak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/355586/original/file-20200831-18-x9b4ak.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/355586/original/file-20200831-18-x9b4ak.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/355586/original/file-20200831-18-x9b4ak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/355586/original/file-20200831-18-x9b4ak.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/355586/original/file-20200831-18-x9b4ak.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The FDA granted emergency use authorization for the test, but only for use on patients with symptoms of COVID-19.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Right-To-Try-Q-And-A/c43323a9a1a94f8eab13bdb3ec0f95d6/6/0">AP Photo/Andrew Harnik, File</a></span>
</figcaption>
</figure>
<h2>What does the Emergency Use Authorization allow for?</h2>
<p>The BinaxNOW test is currently only authorized for patients who have had <a href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">COVID-19 symptoms for seven days or less</a>, which is when virus levels in the body are <a href="https://doi.org/10.1038/s41591-020-0869-5">likely to be high</a>. It must be <a href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">prescribed by a physician and performed by a trained technician</a> or other health care worker. </p>
<p>The PCR test for COVID-19 is currently widely used and <a href="https://theconversation.com/coronavirus-tests-are-pretty-accurate-but-far-from-perfect-136671">considered the gold standard</a>, but requires patient samples to be sent to a lab and can <a href="https://theconversation.com/making-coronavirus-testing-easy-accurate-and-fast-is-critical-to-ending-the-pandemic-the-us-response-is-falling-far-short-142366">take days to provide results</a>. The new antigen test is designed to be a <a href="https://www.sciencemag.org/news/2020/08/milestone-fda-oks-simple-accurate-coronavirus-test-could-cost-just-5#">cheap and quick alternative to PCR testing</a> for diagnostic purposes in a medical setting. It would add critical capacity to an <a href="https://theconversation.com/making-coronavirus-testing-easy-accurate-and-fast-is-critical-to-ending-the-pandemic-the-us-response-is-falling-far-short-142366">overstretched testing system</a>.</p>
<p>The emergency use authorization provides <a href="https://www.fda.gov/emergency-preparedness-and-response/mcm-legal-regulatory-and-policy-framework/emergency-use-authorization">preliminary authorization</a> for doctors to prescribe the antigen test while the full FDA approval process is ongoing. The authorization could be <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-revokes-emergency-use-authorization-chloroquine-and">revoked</a> if the test is not as accurate or reliable as expected.</p>
<p>[<em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>.]</p>
<h2>How accurate is this test?</h2>
<p><a href="https://www.abbott.com/about-abbott.html">Abbott, the health technology company</a> that produces the test, reports that when patients had symptoms the test was in agreement with PCR testing for <a href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">97.1% for COVID-19 positive cases and 98.5% for COVID-19 negative cases</a>. This is <a href="https://www.hcplive.com/view/comparing-rt-pcr-and-chest-ct-for-diagnosing-covid19">high enough for diagnostic settings</a> where accuracy is critical. </p>
<p>However, the true accuracy could be lower because the <a href="https://www.fda.gov/media/141570/download">performance testing group was only 102 people</a> and the accuracy hasn’t been validated by the FDA as part of the full approval process. There will inevitably be some false negatives and false positives with the BinaxNOW test since accuracy isn’t 100%, but the <a href="https://www.fda.gov/regulatory-information/search-fda-guidance-documents/emergency-use-authorization-medical-products-and-related-authorities#monitoring">FDA will monitor the data</a> to make sure the test meets the reported accuracy.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/355590/original/file-20200831-15-kdff8h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="People waiting in a line of cars with health care workers standing under pop-up shade structures." src="https://images.theconversation.com/files/355590/original/file-20200831-15-kdff8h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/355590/original/file-20200831-15-kdff8h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/355590/original/file-20200831-15-kdff8h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/355590/original/file-20200831-15-kdff8h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/355590/original/file-20200831-15-kdff8h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/355590/original/file-20200831-15-kdff8h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/355590/original/file-20200831-15-kdff8h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Long lines and slow turnaround times have limited access to testing, but the new Abbott test should be far easier and faster.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Virus-Outbreak-Nebraska/d964fe543d76489c88a96924b8d02738/72/0">AP Photo/Nati Harnik</a></span>
</figcaption>
</figure>
<h2>Can this test be used for widespread screening?</h2>
<p>The BinaxNOW test is cheap, rapid, able to be mass-produced and easy to use outside a lab. This makes it a promising candidate for <a href="https://theconversation.com/rapid-screening-tests-that-prioritize-speed-over-accuracy-could-be-key-to-ending-the-coronavirus-pandemic-143882">widespread screening</a>. However, the test is currently only authorized for people with COVID-19 symptoms.</p>
<p>This is an obstacle because an estimated <a href="https://theconversation.com/can-people-spread-the-coronavirus-if-they-dont-have-symptoms-5-questions-answered-about-asymptomatic-covid-19-140531">40% of all COVID-19 cases are asymptomatic</a> and these people likely don’t know that they’re contagious. To maximize the effectiveness of any COVID-19 screening program, it is important to test people whether they have symptoms or not.</p>
<p>Health care providers are able to prescribe the BinaxNOW test for asymptomatic patients for <a href="https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/faqs-testing-sars-cov-2?utm_campaign=2020-08-14%20August%2014%20Update:%20New%20Information%20on%20Testing%20for%20SARS-CoV-2&utm_medium=email&utm_source=Eloqua#general-screening-asymptomatic">off-label use</a>, but health officials <a href="https://www.cnbc.com/2020/08/28/abbott-has-trial-of-its-rapid-coronavirus-test-for-asymptomatic-people.html">don’t yet know how accurate the test is</a> when performed on asymptomatic people.</p>
<h2>Is this test a game-changer?</h2>
<p>The massive expansion of testing access made possible by the BinaxNOW test will almost surely outweigh the downsides of a small number of inaccurate results. Abbott plans to manufacture <a href="https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month">50 million tests per month</a> starting in October. This will quickly exceed the <a href="https://covidtracking.com/data/national/tests">76 million COVID-19 tests</a> the U.S. has performed over the last six months.</p>
<p>Widespread, frequent testing is <a href="https://doi.org/10.1101/2020.06.22.20136309">effective at slowing the spread</a> of the coronavirus. The new testing capacity made possible by the authorization of this rapid antigen test represents a major advance in bringing the pandemic under control.</p><img src="https://counter.theconversation.com/content/145285/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Zoë McLaren does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The new BinaxNOW antigen test is quick, easy, accurate and cheap. It could solve the US testing problem, but the emergency use authorization only allows people with COVID-19 symptoms to get tested.Zoë McLaren, Associate Professor of Public Policy, University of Maryland, Baltimore CountyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1438822020-08-14T12:14:45Z2020-08-14T12:14:45ZRapid screening tests that prioritize speed over accuracy could be key to ending the coronavirus pandemic<figure><img src="https://images.theconversation.com/files/352808/original/file-20200813-24-1bm5ubb.jpg?ixlib=rb-1.1.0&rect=48%2C41%2C4535%2C3007&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Broad and frequent screening could catch coronavirus cases before they can spread to others</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/virus-epidemic-concept-biotechnology-research-royalty-free-image/1210724057?adppopup=true"> Vaidas Bucys/EyeEm via Getty Images</a></span></figcaption></figure><p><a href="https://www.nbcnews.com/think/opinion/trump-s-coronavirus-testing-blueprint-isn-t-enough-let-s-ncna1197326">Broad access to testing</a> is one of the most powerful tools to keep the COVID-19 pandemic under control until there’s an effective vaccine in use. <a href="https://www.fda.gov/consumers/consumer-updates/coronavirus-testing-basics">Diagnostic testing</a>, which is used in medical settings to determine whether someone is infected with the coronavirus, is <a href="https://theconversation.com/making-coronavirus-testing-easy-accurate-and-fast-is-critical-to-ending-the-pandemic-the-us-response-is-falling-far-short-142366">costly, slow and overstretched</a> in the U.S. But that’s not the only type of test that can be used.</p>
<p>I <a href="https://scholar.google.com/citations?hl=en&user=t6ZtGJwAAAAJ">study public health policy</a> to combat infectious disease epidemics. To slow the spread of the virus, public health programs need to catch more COVID-19 cases and catch them before they spread. Innovative <a href="https://www.who.int/cancer/prevention/diagnosis-screening/screening/en/">screening tests</a> offer promise because they are inexpensive, rapid, easily mass produced and don’t require laboratory processing. They can be implemented at large scale for frequent testing in schools, workplaces, airports and even at home. With screening tests, huge numbers of people could be tested regularly and contagious people would be identified before they could spread the virus far and wide.</p>
<h2>What is screening testing?</h2>
<p>Ideally, the U.S. could provide frequent, accurate diagnostic testing to the whole population, but diagnostic capacity is <a href="https://theconversation.com/making-coronavirus-testing-easy-accurate-and-fast-is-critical-to-ending-the-pandemic-the-us-response-is-falling-far-short-142366">struggling to keep up with demand</a>. Screening tests make it possible to test large groups of people frequently, including those without any symptoms.</p>
<p>Screening tests are designed to work in a similar way to the X-ray screening of carry-on baggage at airports. X-ray screening is imperfect – some harmless items may prompt a more thorough search and some dangerous items might slip through – but it is fast enough to screen every bag and good enough to catch the majority of potential weapons.</p>
<p>The key, for any screening test, is that it must have a consistent rate of false positives and false negatives. If the user knows exactly how accurate it is, then they can correctly interpret their likelihood of having COVID-19. The Food and Drug Administration generally <a href="https://www.fda.gov/news-events/fda-voices/fdas-ongoing-work-support-and-advance-covid-19-diagnostic-test-accuracy-and-availability">verifies the test accuracy</a> during the approval process, but it could also be done by another government agency.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/352812/original/file-20200813-24-9thpxm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two teachers standing with masks on checking students for fever with temperatures guns" src="https://images.theconversation.com/files/352812/original/file-20200813-24-9thpxm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/352812/original/file-20200813-24-9thpxm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352812/original/file-20200813-24-9thpxm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352812/original/file-20200813-24-9thpxm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352812/original/file-20200813-24-9thpxm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352812/original/file-20200813-24-9thpxm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352812/original/file-20200813-24-9thpxm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=467&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Temperature checks are one form of screening, but miss many COVID-19 cases since 40% of infected people are asymptomatic.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Virus-Outbreak-Texas/5a196377b2d746f4821c0a30f4415600/19/0">AP Photo/LM Otero, File</a></span>
</figcaption>
</figure>
<p>Many fields of public health employ screening test strategies. For example, thermometer-based screening was used during the SARS and Ebola epidemics. Unfortunately, temperature checks miss a lot of COVID-19 cases because an estimated 40% of people with COVID-19 show <a href="https://theconversation.com/can-people-spread-the-coronavirus-if-they-dont-have-symptoms-5-questions-answered-about-asymptomatic-covid-19-140531">no symptoms at all</a>. Many <a href="https://www.washingtonpost.com/powerpost/congress-coronavirus-testing/2020/08/06/716e1ad0-d66d-11ea-aff6-220dd3a14741_story.html">COVID-19 reopening plans</a> incorporate temperature checks since they will catch some cases, but a better screening method is needed.</p>
<h2>Which tests work for COVID-19 screening?</h2>
<p>Several COVID-19 screening tests that <a href="https://www.nytimes.com/2020/08/06/health/rapid-Covid-tests.html">cost $1 to $5 each</a> and <a href="https://theconversation.com/antigen-tests-for-covid-19-are-fast-and-easy-and-could-solve-the-coronavirus-testing-problem-despite-being-somewhat-inaccurate-137977">give a result in around 15 minutes</a> have been developed, and many more are <a href="https://www.nytimes.com/2020/08/06/health/rapid-Covid-tests.html">in the pipeline</a>. These tests don’t require a laboratory and can be processed on-site. Many use <a href="https://www.sciencemag.org/news/2020/08/radical-shift-testing-strategy-needed-reopen-schools-and-businesses-researchers-say">antigen-based testing</a>, which <a href="https://www.fda.gov/consumers/consumer-updates/coronavirus-testing-basics">detects specific proteins</a> on the surface of the virus.</p>
<p>Screening tests come in many different forms. The FDA recently granted <a href="https://www.fda.gov/emergency-preparedness-and-response/mcm-legal-regulatory-and-policy-framework/emergency-use-authorization">Emergency Use Authorization (EUA)</a> to <a href="https://www.quidel.com/sites/default/files/product/documents/EF1439004EN01.pdf">Quidel</a> and <a href="https://www.bd.com/en-us/company/news-and-media/press-releases/bd-launches-portable-rapid-point-of-care-antigen-test-to-detect-sars-cov-2-in-15-minutes-dramatically-expanding-access-to-covid-19-testing">BD</a> for antigen tests that use a small portable point-of-care machine to process samples. Though <a href="https://www.quidel.com/immunoassays/rapid-sars-tests/sofia-sars-antigen-fia">Quidel reports accuracy rates above 95%</a>, the <a href="https://www.fda.gov/media/137884/download">FDA cautions</a> that the rate could be lower because the test hasn’t undergone the full FDA approval process.</p>
<p>One of the most versatile options for testing is the <a href="https://www.fiercebiotech.com/medtech/3m-pairs-mit-to-develop-a-paper-based-coronavirus-diagnostic-test">saliva-based paper-strip test</a>, which only requires a paper strip and a test tube. It could easily be used at home. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/352811/original/file-20200813-24-1fyanga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A man inserting a swab into his mouth while holding tube to contain the sample." src="https://images.theconversation.com/files/352811/original/file-20200813-24-1fyanga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/352811/original/file-20200813-24-1fyanga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352811/original/file-20200813-24-1fyanga.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352811/original/file-20200813-24-1fyanga.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352811/original/file-20200813-24-1fyanga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352811/original/file-20200813-24-1fyanga.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352811/original/file-20200813-24-1fyanga.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A good screening test could be done at home and give results within minutes.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/coronavirus-home-test-royalty-free-image/1254876072?adppopup=true">Circle Creative Studio/E+ via Getty Images</a></span>
</figcaption>
</figure>
<h2>Moderately accurate screening tests still reduce transmission</h2>
<p>Many <a href="https://www.sciencemag.org/news/2020/08/radical-shift-testing-strategy-needed-reopen-schools-and-businesses-researchers-say">inexpensive COVID-19 screening tests</a> <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-posts-new-template-home-and-over-counter-diagnostic-tests-use-non">may not be as accurate</a> as diagnostic tests. But screening tests with even moderate levels of accuracy can actually still <a href="https://doi.org/10.1101/2020.06.22.20136309">effectively slow the spread of the virus</a>, as long as the results are interpreted correctly.</p>
<p>Here’s how this works.</p>
<p>First, frequent testing catches the vast majority of cases. Someone who is infected but gets a false-negative and slips through the cracks is likely to be caught the next time they’re tested. For a test that misses 20% of positive cases, the chance of an infected person getting two false negatives in a row may be as low as 4%. It’s like bailing a boat with a leaky bucket: You just have to bail more quickly to get the job done.</p>
<p>Second, most people who get <a href="https://theconversation.com/coronavirus-tests-are-pretty-accurate-but-far-from-perfect-136671">false-negative results</a> are <a href="https://dx.doi.org/10.1093%2Fcid%2Fciaa619">unlikely to be contagious</a>. Antigen-based screening tests are good at <a href="https://www.sciencemag.org/news/2020/08/radical-shift-testing-strategy-needed-reopen-schools-and-businesses-researchers-say">detecting</a> the <a href="https://dx.doi.org/10.1093%2Fcid%2Fciaa619">high virus levels</a> needed to be contagious. By design, screening tests sacrifice accuracy where it matters least to achieve low costs, speed and ease of use.</p>
<p>Finally, those who get a screening test need to know how to interpret the results. Diagnostic tests can tell you whether you’re infected with a high level of certainty. An inexpensive screening test is not as certain, but is still useful. For example, a positive result would mean that you have a high chance of being contagious, in which case you may want to take a diagnostic test for confirmation and quarantine if possible in the meantime. A negative result would mean that you have a low chance of being contagious, but it couldn’t be ruled out. In this case, it would still be important to stay vigilant about COVID-19 transmission. </p>
<p>While screening tests are not as accurate as diagnostic tests, they are a big improvement over flying blind because they provide useful information about whether someone is contagious. The weather report may not be able to tell you with certainty whether it will rain or not, but it can tell you whether it’s a good idea to bring an umbrella.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/352813/original/file-20200813-18-11nd3l0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A view of a pane of glass with the FDA logo on it with the FDA building in the background" src="https://images.theconversation.com/files/352813/original/file-20200813-18-11nd3l0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/352813/original/file-20200813-18-11nd3l0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352813/original/file-20200813-18-11nd3l0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352813/original/file-20200813-18-11nd3l0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352813/original/file-20200813-18-11nd3l0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352813/original/file-20200813-18-11nd3l0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352813/original/file-20200813-18-11nd3l0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Currently, the FDA has few approval pathways for COVID-19 screening tests, which is a barrier to widespread use.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Virus-Outbreak-New-Testing-Option/a25fb94a759d409bb7054f8281bc49e7/1/0">AP Photo/Jacquelyn Martin, File</a></span>
</figcaption>
</figure>
<p>[<em>Research into coronavirus and other news from science</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-corona-research">Subscribe to The Conversation’s new science newsletter</a>.]</p>
<h2>What’s preventing widespread use of screening tests?</h2>
<p>Several companies are <a href="https://www.nytimes.com/2020/07/03/opinion/coronavirus-tests.html">ready to scale up production of screening tests</a>. The primary barrier is the delay in government approval. It’s difficult for screening tests like <a href="https://www.nytimes.com/2020/07/03/opinion/coronavirus-tests.html">saliva-based paper-strip tests</a> to achieve the performance required for approval as a COVID-19 diagnostic test while remaining inexpensive and easy enough to allow for widespread and frequent testing. By creating <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-posts-new-template-home-and-over-counter-diagnostic-tests-use-non">new approval pathways</a> specifically for screening tests, the FDA or another government agency could quickly put more of these tests into use.</p>
<p>Those who see the potential of rapid screening tests are already taking action. A <a href="https://governor.maryland.gov/2020/08/04/governors-of-maryland-louisiana-massachusetts-michigan-ohio-and-virginia-announce-major-bipartisan-interstate-compact-for-three-million-rapid-antigen-tests/">group of governors</a> plan to secure rapid tests that have been granted an Emergency Use Authorization without waiting for full FDA approval. This will make it easier for those states to get back to in-person school and work safely. It is no exaggeration to say that innovative screening tests are a game-changing tool to fight the coronavirus and keep it at bay.</p><img src="https://counter.theconversation.com/content/143882/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Zoë McLaren does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Testing large numbers of people regularly would reduce the spread of the coronavirus in the US. Laboratory testing is slow and expensive, but rapid screening tests could be the answer.Zoë McLaren, Associate Professor of Public Policy, University of Maryland, Baltimore CountyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1379772020-05-29T12:29:48Z2020-05-29T12:29:48ZAntigen tests for COVID-19 are fast and easy – and could solve the coronavirus testing problem despite being somewhat inaccurate<figure><img src="https://images.theconversation.com/files/338382/original/file-20200528-51445-14cmsye.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5973%2C4365&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Antibodies are incredibly good at finding the coronavirus. Antigen tests put them to work. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/antibodies-responding-to-coronavirus-royalty-free-illustration/1220604943?adppopup=true"> Sergii Iaremenko/Science Photo Library via Getty Images</a></span></figcaption></figure><p>In late February, I fell ill with a fever and a cough. As a biochemist who <a href="https://biology.richmond.edu/faculty/ewu/">teaches a class on viruses</a>, I’d been tracking the outbreak of COVID-19 in China. Inevitably I wondered: Did I have COVID-19, or did I have the flu? </p>
<p>At the time, COVID-19 testing was very restricted but I knew I could get quickly tested for the flu. I drove myself to an urgent care clinic, the nurse easily checked my temperature and took a throat swab and 30 minutes later I got the results: positive for influenza.</p>
<p>The flu test I took is a type of viral screening called a rapid antigen test that looks for viral proteins. For the flu, these antigen tests are <a href="https://www.cdc.gov/flu/professionals/diagnosis/clinician_guidance_ridt.htm">easy to administer, decently accurate and give results almost immediately</a>.</p>
<p>Widespread testing for SARS–CoV–2, the virus that causes COVID-19, is critical to knowing if, when and how people can start to return to their normal lives. An antigen test for the coronavirus could be a huge help in expanding testing.</p>
<p>On May 9, the U.S. Food and Drug Administration approved the <a href="https://www.nytimes.com/2020/05/09/health/antigen-testing-fda-coronavirus.html">first antigen test for emergency use</a> in the U.S. These tests are starting to be available across the country and could dramatically change the COVID-19 testing landscape when they become widely available.</p>
<h2>What is an antigen?</h2>
<p>The human immune system, and in fact the immune systems of most vertebrates, work on a simple idea: Any protein in your body that isn’t encoded by your own genes is probably from a pathogen and should be captured and destroyed. </p>
<p>When the immune system detects a foreign protein, your white blood cells, specifically your <a href="https://www.niaid.nih.gov/research/immune-response-features">B-cells</a>, create antibodies to trap and destroy these proteins. Antibodies are Y-shaped proteins that use their arms as grabbers for foreign proteins. The first round of antibodies aren’t particularly well matched to the shape of a new invading protein, but every time white blood cells make new antibodies, they <a href="https://www.niaid.nih.gov/research/immune-response-features">tweak the shape of the antibody grabber</a> until it fits the protein very well.</p>
<p>The foreign protein that triggers this process is referred to as an “anti–gen” because it is an antibody generator. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/338384/original/file-20200528-51449-1kq0eqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/338384/original/file-20200528-51449-1kq0eqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338384/original/file-20200528-51449-1kq0eqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338384/original/file-20200528-51449-1kq0eqy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338384/original/file-20200528-51449-1kq0eqy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338384/original/file-20200528-51449-1kq0eqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338384/original/file-20200528-51449-1kq0eqy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338384/original/file-20200528-51449-1kq0eqy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The sampling process for an antigen test is easy and fast. A simple throat swab is all that is needed.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Virus-Outbreak-Russia/849081665f854b7eac25593396f2ddfc/16/0">Kirill Zykov, Moscow News Agency photo via AP</a></span>
</figcaption>
</figure>
<h2>How does an antigen test work?</h2>
<p>Antigen tests are well named: They look for antigens. To identify these antigens, antigen tests use antibodies.</p>
<p>You may have performed one yourself if you’ve ever used a home pregnancy test, which uses tests for an antigen called human chorionic gonadotropin in urine that is produced by the cells that surround a fetus when a woman becomes pregnant. </p>
<p>Like the test that diagnoses influenza, the SARS–CoV–2 antigen test uses antibodies that are <a href="https://www.thermofisher.com/us/en/home/life-science/antibodies/antibodies-learning-center/antibodies-resource-library/antibody-methods/introduction-antibody-production-purification.html">produced in animals</a> to hunt for proteins embedded in the coronavirus’s surface. If the antibodies detect viral proteins in a sample, the person most likely has the coronavirus. </p>
<p>An antigen test for SARS-CoV-2 starts with a medical professional collecting a sample of mucus from the back of a persons throat or nose <a href="https://www.cdc.gov/coronavirus/2019-ncov/lab/guidelines-clinical-specimens.html">using a swab</a>. They then dip the swab into a liquid to dissolve the mucus and release the virus. </p>
<p>The liquid is then applied to the surface of the test slide that is coated with antibodies. These antibodies are stuck to the slide and “grab onto” any coronavirus proteins that are in the sample. </p>
<p>A second mixture of antibodies is then applied to the slide. These antibodies have been chemically modified with a dye that makes them visible to the naked eye or detectable by fluorescent light.</p>
<p>If the sample contains viral antigen proteins, those antigens are now sandwiched by two antibodies: one that attaches them to the test kit and another that makes them visible. The more coronavirus antigen there is, the more dye will be visible, indicating that the patient is infected with SARS-CoV-2.</p>
<p>If there is no detectable dye, this would mean the person does not have SARS-CoV-2 or that the sample did not have enough viral proteins.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/338385/original/file-20200528-51496-f37154.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/338385/original/file-20200528-51496-f37154.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338385/original/file-20200528-51496-f37154.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338385/original/file-20200528-51496-f37154.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338385/original/file-20200528-51496-f37154.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338385/original/file-20200528-51496-f37154.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338385/original/file-20200528-51496-f37154.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338385/original/file-20200528-51496-f37154.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Evolution is the greatest engineer in history. By using the immune system itself to search for evidence of a SARS-CoV-2 infection, antigen tests are much faster than normal RNA tests. Antibodies (in blue) binding to a surface protein of SARS-CoV-2 (red).</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/antibodies-binding-to-coronavirus-protein-royalty-free-illustration/1220619673?adppopup=true">Juan Gaertner/Science Photo Library via Getty Images</a></span>
</figcaption>
</figure>
<h2>What are the strengths of antigen tests?</h2>
<p>The main selling points of antigen tests are that they are far faster and easier to perform than reverse transcriptase-polymerase chain reaction (PCR) tests. PCR tests – the swab tests that look for viral RNA – are currently the <a href="https://ourworldindata.org/coronavirus-testing">most common way</a> to test for an active SARS-CoV-2 infection and can take up to <a href="https://www.labcorp.com/tests/139900/2019-novel-coronavirus-covid-19-naa">four days</a> to perform.</p>
<p>By contrast, the most time-consuming part of the antigen test process is waiting for the antibody mixtures and the sample to mix completely. This process takes mere minutes, given the small volumes typically used in an antigen test. A <a href="https://www.quidel.com/immunoassays/rapid-sars-tests/sofia-2-sars-antigen-fia">COVID-19 antigen test</a> might take only 15-30 minutes to complete and requires very little expertise. </p>
<p>Similar tests are done routinely in clinics for influenza all the time. In contrast, PCR tests swabs must be sent to diagnostic laboratories to be performed by experienced technicians as of right now. </p>
<h2>What are the weaknesses?</h2>
<p>What antigen tests gain in speed and ease of use, they lose in accuracy. </p>
<p>Because they look directly for evidence of the virus, there need to be a lot virus proteins available to stick to the antibodies to produce a detectable result. Depending on the virus, qualitative antigen tests likely need a sample to contain <a href="http://www.annclinlabsci.org/content/46/3/282.full.pdf">many thousands of viral proteins</a> in order to produce a positive test. If a sample doesn’t have enough virus or a person has a low-grade infection, the test might give a false negative result – and a sick person would get told they are uninfected.</p>
<p>The Food and Drug Administration <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-first-antigen-test-help-rapid-detection-virus-causes">granted emergency use</a> authorization to a SARS–CoV–2 antigen test made by the pharmaceutical company Quidel Corporation. Quidel reports that their antigen test produces about a <a href="https://www.quidel.com/sites/default/files/product/documents/EF1438900EN00_0.pdf">20% false negative rate</a>. That means that 1 in 5 people who actually are infected will receive a result saying they are not. At a large scale, this may result in missing many infected individuals.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/338386/original/file-20200528-51509-7txv4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/338386/original/file-20200528-51509-7txv4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338386/original/file-20200528-51509-7txv4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=323&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338386/original/file-20200528-51509-7txv4u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=323&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338386/original/file-20200528-51509-7txv4u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=323&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338386/original/file-20200528-51509-7txv4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=406&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338386/original/file-20200528-51509-7txv4u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=406&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338386/original/file-20200528-51509-7txv4u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=406&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Antigen tests are already used to test for the flu and pregnancy. Why not for COVID-19?</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/doctor-holding-a-test-kit-for-viral-disease-covid-royalty-free-image/1218593811?adppopup=true">TravelCouples/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>Can I get one?</h2>
<p>The Quidel test is not currently widely available due to <a href="https://www.investors.com/news/technology/coronavirus-test-quidel-antign-appoach-game-changer/">production capacity</a>. As production ramps up and other companies begin to produce antigen tests, they will become more available. Once laboratories around the country begin processing the antigen tests, public health officials will also get a better sense of the real-world false negative rate. </p>
<p>A COVID-19 antigen test can fill an important gap in the testing landscape by providing fast diagnoses in the clinic, but they’re not perfect. Because of the somewhat high false negative rate, individual patients should be careful with how they interpret the results. But when combined with more accurate PCR tests and blood tests that look for antibodies, antigen testing has a large role to play in helping public health officials better understand and fight the spread of the coronavirus. </p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-understand">Subscribe to The Conversation’s new science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/137977/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eugene Wu does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>An antigen test was given emergency use authorization by the FDA in early May. A biochemist explains how COVID-19 antigen tests work.Eugene Wu, Associate Professor of Biology and Biochemistry, University of RichmondLicensed as Creative Commons – attribution, no derivatives.