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Juan Lama
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Rapid Antigen Tests (RAT) have become an invaluable tool for combating the COVID-19 pandemic. However, concerns have been raised regarding the ability of existing RATs to effectively detect emerging SARS-CoV-2 variants. We compared the performance of eight commercially available, emergency use authorized RATs against the Delta and Omicron SARS-CoV-2 variants using individual patient and serially diluted pooled clinical samples. The RATs exhibited lower sensitivity for Omicron samples when using PCR Cycle threshold (CT) value (a proxy for RNA concentration) as the comparator. Interestingly, however, they exhibited similar sensitivity for Omicron and Delta samples when using quantitative antigen concentration as the comparator. We further found that the Omicron samples had lower ratios of antigen to RNA, which offers a potential explanation for the apparent lower sensitivity of RATs for that variant when using CT value as a reference. Our findings underscore the complexity in assessing RAT performance against emerging variants and highlight the need for ongoing evaluation in the face of changing population immunity and virus evolution. Preprint available in medRxiv (Feb. 10, 2023): https://doi.org/10.1101/2023.02.09.23285583
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Juan Lama
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If you have symptoms but get a negative home test result, you may need to keep taking precautions and test again (and again). What does a negative result on a home Covid-19 test really mean That’s the question that has confounded many people who have reached for a home test because they have a sore throat, cough or runny nose. After swabbing their nose and waiting an anxious 15 minutes, the result is negative. While there’s relief in getting a negative result, there’s also uncertainty. Am I really free of Covid? Or did the test just not detect it? Should I test again? Can I spend time with other people. The confusion is justified, say testing and public health experts. It stems from a lack of understanding about how the tests work. Rapid home antigen tests look for pieces of viral proteins from a swab of your nose, and they are designed to identify whether you have an infectious level of the virus. But a negative test is not a guarantee you don’t have Covid. It could be that your symptoms are an immune response signaling the arrival of Covid or another invader. The harder your immune system is working to tamp down the virus, particularly an immune system supercharged by vaccine antibodies, the more likely you are to get an early negative result on a rapid test, even if you’re infected. “It may be that the virus in your body is having a tug of war with your immune system,” said Dr. Michael Mina, chief science officer for eMed, a company that helps rapid test users get treatment from home. “If you test negative and you have symptoms, don’t assume you’re negative. Assume that the virus has not had an opportunity to grow up yet. The symptoms might mean your immune system is just triggering a very early warning.” Dr. Mina advises people to take a rapid test on the first day of symptoms. A positive result means you almost certainly have Covid. If the result is negative and your symptoms continue, you should still take precautions, wear a mask and avoid close contact with other people. If you can’t test daily, then wait 48 hours and test again. If you’re still negative but your symptoms persist or are getting worse, you should take another test on Day 4. Or you may want to go to a testing center to take a P.C.R. test, which can sometimes detect Covid a little sooner than a home test, although you may have to wait a day or two for the results. Experts say that if you have symptoms and continue to get negative results on home tests, it may be that your immune system is doing a good job beating the virus. Or it could be that you have another illness. Either way, you should try to avoid infecting others. “If you have symptoms and continue to test negative, the chances that you’re infectious with Covid have gone down a lot,” said Dr. Robert Wachter, the chair of the medicine department at the University of California, San Francisco. “But you probably should wear a mask that day because you have something.” And, remember, the result of your home test is just one piece of information. If you haven’t left the house in weeks, your negative result after a few tests is probably accurate. If you have symptoms and you’ve been spending time in bars or a family member has been exposed to Covid, you should be more cautious, even if the initial results are negative. It may be that you tested too early and that your viral load isn’t high enough to be detected. When Dr. Jillian Horton, an internal medicine doctor in Winnipeg, started feeling ill, she was pretty sure she had Covid. Her husband had been exposed and had symptoms, too. She decided to conduct an experiment of one, testing herself several times over the course of a few days to track the dynamics of the virus. “With my husband testing positive and myself very symptomatic, I was sure I had Covid,” Dr. Horton said. “I was curious to see what I could pinpoint in terms of when I might flip positive.” Dr. Horton’s husband became ill on a Friday night, and that evening she tested negative. On Saturday, she began to feel sick and tested herself three times throughout the day. All three results were negative. By Sunday morning, she woke up and was feeling worse. At 6 a.m. she tested and saw a faint line on the test — what she called a “weak positive.” She took two more tests on Sunday and both were negative. On Monday morning, she tested again, and the test rapidly turned positive. What is notable about Dr. Horton’s experiment is that if she had tested at a different time on Sunday, she may never have discovered the weak positive. Her immune system was clearly battling the virus, as evidenced by her two negative test results later in the day. Dr. Horton noted that testing at the right time to catch a high viral load was similar to putting a net in a stream. If the fish aren’t there, you won’t catch anything. But if you time it so that the fish are plentiful, you’ll catch your dinner. Dr. Horton said she was concerned that too many people think the tests aren’t working when, in fact, they are a useful tool if you understand how to use them. They are ideal for “ruling in” Covid, but you have to consider more information when evaluating a negative test. “So often I hear people say, ‘The test is useless,’” Dr. Horton said. “What my experience illustrated is that when you have symptoms, the tests are really ‘rule-in’ tests. I think of those two days when I was so symptomatic. I had one positive test and five negative tests. There was only one moment in there where I was more infectious.” Linsey Marr, a professor of civil and environmental engineering at Virginia Tech and one of the world’s leading experts on viral transmission, said she assumed her daughter had Covid even after a rapid test came back negative. The child had a fever and sore throat, and she had been exposed to Covid through her gymnastics team. But testing proved useful for knowing that her daughter wasn’t highly contagious, which helped Dr. Marr’s family know how to manage the risk. “We knew we needed to be careful,” Dr. Marr said. “But we didn’t have to totally put her in jail. The test told us that the viral load was not high enough that we had to lock her in her room and be that worried about all of us getting it.” Instead, the family wore masks and opened windows to improve ventilation. Kristina Kasparian, who works from home in Montreal, believes she may have gotten Covid from her husband, who is a schoolteacher. They disagreed on whether a home test he took showed a faint positive. But a few days later she woke up with tightness in her chest and a sore throat. Her test was positive, and her husband has continued to test negative. “It’s great to have this tool, but it’s such a variable snapshot in time,” she said. Dr. Mina said that despite the limitations, people would benefit from frequent testing any time they suspect they have been exposed, have symptoms or want to be sure they are not infectious before spending time with a person at high risk. He also recommends testing before you start interacting with others again to be sure you’re not still infectious. “These are tools that have massive benefit during a pandemic like this,” Dr. Mina said. “They will catch you when you’re most infectious. They will even catch you most of the time when you’re just slightly infectious. They will catch almost everyone when they have a high enough viral load to spread. But it won’t be perfect.”
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Juan Lama
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The emergence of the SARS-CoV-2 Omicron variant has motivated a re-evaluation of the test characteristics for lateral flow immunochromatographic assays (LFIAs), commonly referred to as rapid antigen tests. To address this need, we evaluated the analytic sensitivity of one of the most widely used LFIAs in the US market, the Abbott BinaxNOW COVID-19 Ag At-Home Card using 32 samples of Omicron and 30 samples of the Delta variant. Samples were chosen to intentionally over-represent the range of viral loads where differences are most likely to appear. We found no changes in the analytic sensitivity of the BinaxNOW assay by variant even after controlling for variation in cycle threshold values in the two populations. Similar to prior studies, the sensitivity of the assay is highly dependent on the amount of virus present in the sample. While the analytic sensitivity of the BinaxNOW LFIA remains intact versus the Omicron variant, its clinical sensitivity is influenced by the interaction between viral replication, the dynamics of tissue tropism and the timing of sampling. Further research is necessary to optimally adapt current testing strategies to robustly detect early infection by the Omicron variant to prevent transmission. Preprint available in medRxiv (Jan. 11, 2022): https://doi.org/10.1101/2022.01.10.22269033
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A new study raises significant doubts about whether at-home rapid antigen tests can detect the Omicron variant before infected people can transmit the virus to others. The study looks at 30 people from settings including Broadway theaters and offices in New York and San Francisco where some workers were not only being tested daily but were, because of rules at their workplaces, receiving both the antigen tests and a daily test that used the polymerase chain reaction, or PCR, which is believed to be more reliable. On days 0 and 1 following a positive PCR test, all of the antigen tests used produced false-negative results, even though in 28 of the 30 cases, levels of virus detected by the PCR test were high enough to infect other people. In four cases, researchers were able to confirm that infected people transmitted the virus to others during the period before they had a positive result on the rapid antigen test. “I think that with every new variant that comes, scientists have to question whether the things that were previously true are still true,” said Blythe Adamson, the lead author of the paper and the principal epidemiologist at Infectious Economics in New York. “This one has a different way it travels, a different mechanism of action of symptoms, it has different windows of transmission.” Adamson, who is also an employee of Flatiron Health, an affiliate of Roche, said that it was also possible there were more cases of transmission than the authors were able to confirm. “It’s absolutely likely there were many more than four transmissions,” Adamson said. “We named four because there were four that were confirmed through contact tracing and epidemiology investigation. There were likely many more.” The study included both the Abbott BinaxNOW and Quidel QuickVue rapid antigen tests, both of which are authorized by the Food and Drug Administration. The results were published in a preprint, meaning they have not yet been reviewed by outside researchers. The results mean that rapid tests — both Abbott BinaxNOW and Quidel QuickVue — aren’t catching people during their first couple days of infection. “We know that PCR tests are more sensitive than antigen tests — this is not new information,” Abbott Laboratories said in a statement. “We also know that PCR tests are so sensitive that they do not indicate infectiousness and thus are not a practical tool for keeping the workforce and economy moving.” Despite its small size, the results in the study are remarkably consistent. Not a single rapid antigen test detected the virus until nearly two days after the initial positive PCR result. Additionally, the cases of infection from people who had received false negative results could raise alarm bells. Daniel Larremore, an assistant professor of computer science at the University of Colorado Boulder who has studied Covid testing, said the results show rapid tests are not catching cases during the first days of infection. Meanwhile, people are facing hour-long lines for PCR tests and multiple-day waits for results. “[The] results strongly suggest that we will be unable to effectively test our way out of the current surge, even if we each had a week’s supply of rapid tests on the counter,” Larremore said. He was not involved with this study. Other data from the group indicate that viral loads peaked in saliva one to two days before they peaked in tests taken from nasal swabs, adding to evidence that swabs taken from the mouth or throat may detect the SARS-CoV-2 that causes Covid better than the nasal swabs used for many PCR and antigen tests. “The major unknown is what it has been for weeks now: Are the [rapid antigen tests] inherently less able to detect Omicron, or is there less Omicron to detect on nasal swabs?” asked John Moore, a professor of microbiology and immunology at Weill Cornell Medical College. He noted that a paper from South Africa had also shown that there was more virus in saliva than in the nose. “Does it replicate more in the throat/mouth and hence accumulates in saliva, more than it does in the nose and is present on nasal swabs?” Moore asked. “Remember that Omicron infections are not generally causing loss of smell, which happens when the virus damages nasal tissue and the nerves within the tissues. Is that another indicator of less replication in the nose?” At this point, researchers see riddles, not solutions. However, many emphasize, this does not mean that rapid antigen tests are not useful. The tests also detected the virus in every case – it just took longer than with PCR. So while the tests may not work as an early warning, a positive test result at home does likely mean that the person taking the test has Covid-19. Anne Wyllie, a researcher at the Yale School of Public Health and a co-author on the paper, said that the reports she is seeing from the general public on social media also raise her level of concern. “If the general public is seeing this and reporting on it, you know, this is also a lot of evidence for me,” Wyllie said. “Like they’re actually seeing it. This is a lot more widespread than just this one outbreak that we were observing.” During the pandemic, Adamson and Infectious Economics became consultants to many Broadway productions that were trying to keep their staffs safe from Covid. The risk to audiences was relatively easy to control, but cast and crew members worked in cramped quarters where lots of safety precautions, including vaccination, masking, and the use of rapid tests were all necessary to keep people safe. She said that as soon as Omicron hit, there were anecdotes about rapid antigen tests remaining negative until days after the infected people had already developed symptoms. She said she started to feel anxiety about whether precautions to keep cast members safe would be enough. Since then, numerous Broadway shows, including “Waitress” and “Jagged Little Pill,” have announced Covid-related closures. Cited Findings Available at medRxiv (Jan. 5, 2022): https://doi.org/10.1101/2022.01.04.22268770
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Juan Lama
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Unlike similar at-home tests, Ellume’s does not require a prescription. The Food and Drug Administration on Tuesday issued an emergency authorization for the country’s first coronavirus test that can run from start to finish at home without the need for a prescription. People as young as 2 years old are cleared to use the test, which takes just 15 to 20 minutes to deliver a result. Unlike many similar products, which are only supposed to be used by people with symptoms of Covid-19, this test is authorized for people with or without symptoms. The test, developed by the Australian company Ellume, detects bits of coronavirus proteins called antigens. It’s slightly less accurate than gold standard laboratory tests designed to look for coronavirus genetic material with a technique called polymerase chain reaction, or P.C.R. But in a clinical study of nearly 200 people, Ellume’s product was able to detect 95 percent of the coronavirus infections found by P.C.R., regardless of whether the infected people felt sick. It also correctly identified 97 percent of the people who received negative laboratory test results. Ellume, which was awarded a $30 million grant from the National Institutes of Health, said it planned to manufacture and deliver about 20 million home coronavirus tests to the United States within the first half of 2021. Each kit, which tests a single swab sample, is expected to cost about $30 or less, said Bella Zabinofsky, a spokeswoman for the company. In a statement, the F.D.A. commissioner Dr. Stephen M. Hahn called Ellume’s authorization “a major milestone in diagnostic testing for Covid-19” in light of the coronavirus’s persistent grip on the nation. The product will be available in drugstores, Dr. Hahn noted, and gives Americans “more testing options from the comfort and safety of their own homes.” Ellume’s test works best in people with Covid symptoms. In people without symptoms, the product’s accuracy dropped a bit, finding 91 percent of the coronavirus infections discovered by P.C.R. Dr. Valerie Fitzhugh, a pathologist at Rutgers University, noted that all of the study’s false positives occurred in the asymptomatic group. That “does make me a little nervous,” Dr. Fitzhugh said. False positives could send people into unnecessary periods of isolation or erode trust in testing, among other issues. In a statement announcing Ellume’s emergency clearance, the F.D.A. underscored the importance of recognizing false positive and false negative results, both of which are more common with antigen tests. People without symptoms who test positive, the agency said, should confirm their results with another test, especially if the coronavirus is scarce in their community. When very few people in a region are infected, the number of false positives yielded by tests can outnumber true positives. Still, in broad strokes, “the performance looks better than what we’ve seen for other antigen tests,” said Susan Butler-Wu, a clinical microbiologist at the University of Southern California’s Keck School of Medicine. The test’s price tag — compared with some competitors that cost just $5, for example — and limited availability will likely restrict it from very frequent use, Dr. Butler-Wu said. But in single-use contexts, “what’s really exciting is, it allows me to get a really quick answer if I’m feeling unwell. To me, that’s the most powerful thing.” FDA EUA Letter (Dec. 15, 2020): https://www.fda.gov/media/144457/download
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Juan Lama
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In a small study in San Francisco, Abbott’s BinaxNOW identified infectious people nearly as accurately as a P.C.R. test. A $5 rapid test for the coronavirus may be nearly as effective as the slower, more complex polymerase chain reaction test for identifying people who may spread the coronavirus, a novel experiment has found. The study, conducted by scientists at the University of California, San Francisco, is among the first head-to-head comparisons of a rapid test and the P.C.R. diagnostic tool under real-world conditions. But the number of participants was comparatively small, and the data have not been peer-reviewed or published. A rapid test still cannot conclusively determine that an individual is not infected; the tests are intended primarily to detect the presence of high levels of the virus, rather than its absence, and are authorized only to evaluate symptomatic people. At the moment, anyone who has been exposed to the virus should be tested by P.C.R., said Joseph DeRisi, an infectious disease expert at U.C.S.F. and a co-leader of the project. At the moment, anyone who has been exposed to the virus should be tested by P.C.R., said Joseph DeRisi, an infectious disease expert at U.C.S.F. and a co-leader of the project. The new test, Abbott’s BinaxNOW, offers results in 15 minutes, compared with the days or weeks people may have to wait for a P.C.R. result. The Trump administration already has purchased 150 million BinaxNOW tests and plans to ship them to states for use in schools, nursing homes and meatpacking plants. The tests could also be used to screen people in communities where time, trust and resources are in short supply. The study assessed the BinaxNOW in one such community, a largely Latino neighborhood in San Francisco. On three mornings in late September, as commuters emerged from a BART train station in the Mission District, they were offered two nasal swabs: one for a P.C.R. test, the other for the rapid test with a simple readout. The commuters received only the P.C.R. result, by text, but the researchers compared both tests. Of the 878 people who took the tests at the train station, only 26 tested positive on the researchers’ P.C.R. BinaxNOW identified only 15 of them. But many experts have argued that the P.C.R. test is too sensitive, picking up fragments of the coronavirus lingering in the body long after people have recovered and are no longer infectious. A study by the company Becton Dickinson recently showed that rapid tests correlated better with live virus than P.C.R. But when they only considered P.C.R. results that corresponded to high viral loads, the researchers found that the BinaxNOW test detected 15 of the 16 people who were most likely to transmit the virus... Preprint available at medRxiv (October 5, 2020): https://doi.org/10.1101/2020.10.02.20205708
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The Food and Drug Administration has approved the first antigen test that can rapidly detect whether a person has been infected by the coronavirus, a significant advancement that promises to greatly expand the nation’s testing capacity. The test, by the Quidel Corporation of San Diego, was given emergency use authorization late Friday by the F.D.A., according to a notice on the agency’s website. Unlike commonly available coronavirus tests that use polymerase chain reaction, or PCR, antigen diagnostics work by quickly detecting fragments of virus in a sample. The newly approved Quidel test will rely on specimens collected from nasal swabs, according to the F.D.A., and they can only be processed by the company’s lab instruments. “Diagnostic testing is one of the pillars of our nation’s response to Covid-19, and the F.D.A. continues to take actions to help make these critical products available,” the agency said in a statement on Saturday. “One of the main advantages of an antigen test is the speed of the test, which can provide results in minutes.” The F.D.A. said it expects to grant emergency clearance for other antigen tests in the near future. FDA Letter of Emergency Use Authorization (May 8, 2020) : https://www.fda.gov/media/137886/download
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WASHINGTON, Dec 15 (Reuters) - U.S. households can order four free at-home COVID-19 tests from the government website COVIDTests.gov beginning on Thursday as part of the Biden administration's efforts to tackle coronavirus infections over the winter. The White House said it would use existing funding to pay for the tests since it has been unsuccessful so far in getting Congress to pass a bill to put more money toward the U.S. COVID-19 response. The free tests program was paused because officials wanted to make sure there were enough tests available for a likely spike in COVID cases in the winter, White House COVID-19 response coordinator Ashish Jha said. "We knew there will be a moment later in the year when COVID cases would rise again. So we preserved the tests so we could have them on hand for exactly this moment," White House COVID-19 response coordinator Ashish Jha said on Thursday. "And if we don't get more funding, we won't be able to send more tests out to the American people." White House Press Release (Dec. 15, 2022): https://www.whitehouse.gov/briefing-room/statements-releases/2022/12/15/fact-sheet-biden-administration-announces-covid-19-winter-preparedness-plan/
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In 731 persons seeking COVID-19 testing at a walk-up San Francisco community site in January 2022, simultaneous nasal rapid antigen testing (BinaxNOW(TM)) and RT-PCR testing was performed. There were 296 (40.5%) positive tests by RT-PCR; 98.5% of a random sample (N=67) were the omicron variant. Sensitivity of a single antigen test was 95.2% (95% CI 92-98%); 82.1% (95% CI 77-87%) and 65.2% (95% CI 60-71%) for Ct threshold of < 30, < 35 and no threshold, respectively. We also compared BinaxNOW(TM) to RT-PCR from oral cheek swabs to nasal swabs (N=75); oral cheek specimen was significantly less sensitive than nasal swab. A single BinaxNOW(TM) oral cheek rapid antigen test failed to detect 91% (20 of 22) of specimens that were BinaxNOW(TM) positive from the standard nasal sampling. In a separate direct comparison of BinaxNOW(TM) between specimens collected from nasal or throat (tonsillar) swab (N=115), sensitivity was 97.7% for nasal and 48.8% for throat swabs that were PCR-positive on nasal swab with a Ct threshold < 30. Among persons with either a nasal or throat RT-PCR positive swab with Ct<30, BinaxNOW(TM) sensitivity was 85.7% for nasal and 89.8% for nasal plus throat swabs. BinaxNOW continues to be a very useful diagnostic during the omicron surge; oral (throat or cheek swab) should not replace nasal swabs due to significantly reduced sensitivity compared to nasal. As currently recommended, repeat testing should be done for high-risk persons with an initial negative antigen test result. Preprint available in medRxiv (Jan. 19, 2022): https://doi.org/10.1101/2022.01.08.22268954
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A new study adds to evidence that common rapid tests may fail to detect some Omicron cases in the first days of infection. A small, new real-world study suggests that two widely used at-home antigen tests, the Abbott BinaxNOW and Quidel QuickVue, may fail to detect some Omicron infections even when people are carrying high levels of the coronavirus. The study, which has not yet been peer-reviewed, focused on 30 people infected with the virus at five workplaces that experienced what were most likely outbreaks of the Omicron variant in December. The people received both saliva-based P.C.R. tests and rapid antigen tests using nasal swabs. It took three days, on average, for people to test positive on a rapid antigen test after their first positive P.C.R. result. In four cases, people transmitted the virus to others while the rapid test showed the negative result, according to the study, which was conducted by several members of the Covid-19 Sports and Society Working Group. It is not clear whether the infections were missed because the antigen tests are inherently less sensitive to Omicron or because saliva tests may be better at detecting the new variant. But the results are consistent with other preliminary evidence that the at-home tests that many Americans have come to rely on — at least as currently administered, with a nasal swab — may fail to detect some Omicron cases in the first days of infection. The researchers said they shared their results with federal officials — including at the White House, the Food and Drug Administration and the Centers for Disease Control and Prevention — in real-time, as the outbreaks were occurring last month. “They’re aware that there are flaws with antigen testing,” said Dr. Robby Sikka, an author of the study and chair of the working group. The study comes a week after the Food and Drug Administration released its own update on the effectiveness of the rapid antigen tests. “Early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity,” the agency said. Many of the studies are early and small, and much more data is needed. The tests, which can deliver results at home in minutes, remain an important public health tool, and positive results are especially likely to be informative, many scientists said. (The wait for P.C.R. results can stretch for days.) “The message is not that we should stop using these tests,” said Isabella Eckerle, a clinical virologist at the University of Geneva in Switzerland. But people should be cautious about interpreting negative results, especially when they have symptoms or believe they may have been exposed to the virus. “It’s not a ticket that allows you to go back to normal or to drop any other measures,” Dr. Eckerle said. Antigen tests are designed to detect proteins on the surface of the coronavirus. If mutations in the virus change the structure of these proteins, antigen tests might fail to detect the variant. The Omicron variant has about 50 mutations, including more than 30 on the spike protein alone. Most rapid antigen tests are designed to detect more stable targets, which are far less mutated in Omicron. Still, even minor-seeming mutations can affect a virus’s surface proteins, “sometimes in non-obvious ways,” said John Moore, a virologist at Weill Cornell Medicine. “Only experimental data can determine whether there is an impact or not.” The F.D.A. in September told makers of rapid tests that they would be required to continue to test their products as new variants emerged, and, if asked, to share those results with the agency. Many companies have announced that their tests can detect Omicron, and several independent scientists said that they believed the tests should be capable of recognizing the variant, especially when present at high levels. But a few new studies raise questions about the tests’ sensitivity. The F.D.A.’s update stemmed from an evaluation it is doing with the National Institutes of Health, said Bruce Tromberg, director of the National Institute of Biomedical Imaging and Bioengineering. The scientists evaluated the antigen tests using pooled samples of nasal mucus collected from multiple people with Omicron, as well as similar pooled samples from Delta patients. Scientists then diluted each of these pooled samples until the antigen tests no longer detected the virus. The tests were able to detect more dilute solutions of Delta samples than Omicron samples, suggesting that the tests may be less sensitive to the new variant, Dr. Tromberg said. Still, he added, in real-world settings, “it may not translate into any different sensitivity.” An F.D.A. spokeswoman, Stephanie Caccomo, said last week that studies were underway “to confirm the reason for the apparent decreased sensitivity.” “Once that is known,” she said, “adjustments to existing tests can be undertaken by each developer with support from the F.D.A., if appropriate.” The F.D.A. update was not the first hint that some antigen tests may be less sensitive to Omicron. Dr. Eckerle and her colleagues recently evaluated the performance of seven antigen tests against samples of the virus grown from specimens taken from people infected with Omicron. Overall, the researchers found, the tests were less sensitive to Omicron than to previous variants. “They missed samples with infectious virus, and they missed samples that had quite a decent viral load,” Dr. Eckerle said. The work has not yet been published in a scientific journal. But there was also vast variability in the performance of the different tests, most of which are not available in the United States. And an Australian study, which examined a mostly different collection of antigen tests, found that the tests had a similar sensitivity to Omicron and Delta. More data are needed, experts said. “Each test is going to have to be evaluated independently any time there’s a new variant,” said David O’Connor, a virologist at the University of Wisconsin, Madison who urged people not to stop using rapid tests. “And that takes some time.” The new study focused on five New York and California workplaces that had virus outbreaks in December. In 29 of 30 people, samples of the virus produced a telltale genetic pattern on P.C.R. tests, suggesting that these individuals were most likely infected with Omicron. Each participant took P.C.R. and antigen tests daily over a period of up to 10 days. The discordant results overwhelmingly came during the first three days of infection. “A negative result may not actually be a negative result,” said Anne Wyllie, a microbiologist at the Yale School of Public Health and an author of the new study. “People should not ignore high risk exposures. They should not ignore symptoms.” The study’s other authors are Blythe Adamson, the founder of Infectious Economics, a public health consulting company, and Dr. Prem Premsrirut, the chief executive of Mirimus Laboratories, which offers saliva-based P.C.R. testing. An Abbott spokesman, John Koval, said on Wednesday that the finding that a P.C.R. test is more sensitive is “not new.” “Due to immediate turnaround time, frequent rapid antigen testing does slow transmission — and with a highly infectious variant frequent testing is needed, which is not realistic with P.C.R.,” he wrote in an email. Quidel’s president, Douglas Bryant, said in a statement that the company performed recent testing using samples from South Africa and confirmed that its rapid tests are detecting the Omicron variant. A company spokesperson also said that it was not surprising that saliva-based P.C.R. tests detected the virus before nasal swabs did, if the study accurately concluded that viral load peaks first in saliva. The company noted that its rapid tests only have F.D.A. clearance to collect nasal swab specimens. In a smaller analysis, of five participants who took both nasal and saliva-based P.C.R. tests, the researchers found that the levels of virus peaked in saliva samples a day or two before they peaked in samples collected from the nose. Those findings are consistent with a recent report from South Africa, which has not yet been reviewed by experts. The researchers found that P.C.R. tests picked up a higher share of Omicron infections when saliva samples — produced by the rubbing of a swab inside the cheeks, around the gums and tongue — were used instead of nasal samples. The reverse was true for Delta. “Ideally, until we can directly compare the relative sensitivity of the antigen tests, my suggestion would be to test both sites,” Diana Hardie, a clinical virologist at the University of Cape Town, who led the research, said in an email. One possible explanation for the findings is that Omicron replicates faster or earlier in the throat and mouth than in the nose. “While we’ll have to wait to see if the science bears out, that might be an indicator that that’s where the virus is growing first,” said Gigi Gronvall, an immunologist and testing expert at Johns Hopkins Bloomberg School of Public Health. “So if you’re going to look for the virus, which is what the tests do, then you may find more of it faster in the throat swab over the nose.” Anecdotal reports have also emerged that some people who tested negative on antigen tests when they swabbed inside their noses received a positive result when they instead swabbed the back of their throats. “There’s a lot of chatter around this,” said Nathan Grubaugh, a virologist at the Yale School of Public Health. “Obviously, that warrants further investigation.” Some tests available in Britain call for swabbing both the nose and the throat, but the antigen tests available in the United States are not authorized for the collection of saliva or samples from the throat. Omicron’s rapid replication also means that there is a narrower window to catch the virus before it begins spreading, and that people may need to test themselves sooner after a potential exposure and as close as possible to an upcoming gathering or event, experts said. They may also need to test themselves more frequently overall, a particular challenge when the tests are in short supply. People who may have been exposed to the virus should take at least two antigen tests over the course of about two days, experts said.
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- First at-home, virtually guided service to bring rapid, reliable and affordable testing into the home where the result is delivered in minutes - Abbott and eMed™ expect to deliver and administer 30 million BinaxNOW™ tests in the first quarter of 2021, with an additional 90 million in the second quarter - $25 cost for the test and service is the lowest available for at-home testing, which supports the home user to ensure a successful testing process - BinaxNOW is a highly portable, easy-to-use, 15-minute antigen test with no instrument that detects the virus when people are most infectious, which is critically important in slowing the spread of the virus - Service uses Abbott's complementary NAVICA™ app to enable the testing process and display authenticated BinaxNOW test results verified by a trained guide - and supports consumer confidence in testing at home ABBOTT PARK, Ill.,, Dec. 16, 2020 /PRNewswire/ -- Abbott (NYSE: ABT) announced today that the U.S. Food and Drug Administration (FDA) has issued Emergency Use Authorization (EUA) for virtually guided at-home use of its BinaxNOW™ COVID-19 Ag Card rapid test for detection of COVID-19 infection. Abbott is bringing BinaxNOW, the most affordable and widely distributed rapid test into the home, where the result is delivered in minutes without the need to send it out for processing. The $25 cost for the test and service is the lowest currently available for at-home testing. To facilitate the delivery of the BinaxNOW test to the home and the guided collection and testing process, Abbott has partnered with digital health solutions provider eMed™. This agreement furthers Abbott's vision of making as many tests as possible available in a variety of different settings to improve accessibility, support consumer confidence in testing at home, and help people start returning to living their daily lives with more normalcy. Abbott and eMed expect to deliver and administer 30 million BinaxNOW at-home tests in the first quarter of 2021, with an additional 90 million in the second quarter. Scale is critical to provide broad access to people who need testing and Abbott has scale for all its eight COVID-19 lab and rapid tests. In fact, since launching BinaxNOW in August, Abbott has ramped up capacity to 50 million tests a month in its U.S. facilities that are currently being distributed through the federal government and is expanding further so even more people have access to the tests. "As the pandemic has evolved, the need for rapid testing has only grown. Unfortunately, we're still hearing that many people can't access testing as quickly as they need it," said Robert B. Ford, Abbott's president and chief executive officer. "That's why Abbott is bringing our rapid BinaxNOW test and NAVICA platform into homes through this partnership with eMed, which allows us to maintain the integrity of the testing process, get even closer to people who need testing and help provide the confidence we need to help get back to living with a bit more normalcy." The eMed service offering costs $25 a test, and eMed takes care of determining eligibility, the guided self-collection process, public health reporting requirements and gets people their results through their NAVICA app in a matter of minutes. The eMed offering could also remove some of the obstacles that individuals, governments and organizations face when seeking to provide or perform testing. These include mobility issues for people with disabilities or who may not have a reliable form of transportation, inconvenient testing windows for people who work non-traditional hours or have childcare or eldercare responsibilities, and discouragingly long lines at testing centers. FDA Release Dec. 16, 2020: https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-issues-new-authorization-binaxnow-covid-19-ag-card-home-test
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Rapid antigen tests for the coronavirus are faster, cheaper and more user-friendly than standard diagnostic assays. An assessment now shows that some antigen tests — but not all — can tell with high accuracy who is likely to be most infectious. Antigen-based assays detect specific proteins, or antigens, on the surface of SARS-CoV-2 particles. Christian Drosten at the Charité — University Hospital Berlin and his colleagues analysed the performance of seven commercially available rapid antigen tests. The researchers applied the tests to a range of samples, including dozens of swabs from people who had already tested positive for SARS-CoV-2 or for other respiratory viruses using the gold-standard polymerase chain reaction test (V. M. Corman et al. Preprint at medRxiv https://doi.org/ghj3wt; 2020). The five most sensitive antigen assays detected the presence of SARS-CoV-2 on 95% of the test runs for samples with concentrations of viral genetic material that ranged between the equivalent of 3.4 million and 74 million copies per millilitre of swab. Such high viral levels are observed during the first week of symptoms, when people are likely to spread the virus to others. The findings have not yet been peer reviewed. Study cited available as preprint in medRxiv (November 13, 2020): https://doi.org/10.1101/2020.11.12.20230292
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An 18-year old high school senior from the Houston area mobilized his medical knowledge as one of the youngest EMTs in Texas and co-founded a mobile lab which can provide COVID-19 results in 15 minutes. Texas Mobile Medical Labs was created to counteract testing delays that bogged down how quickly patients received results. The mobile lab currently operates in a van and a tent outside a community center in the Post Oak area for patients who prefer to come to them. For those that can't, the mobile lab can travel to any patient or business location for employee testing in the Houston area after they set up an appointment. "This summer I become an EMT, training at the Texas EMS Academy in Corpus Christi," says Taft Foley III, co-founder of Texas Mobile Medical Labs. "When I got back to Houston I was asked to take a COVID-19 test, but I was met with a line that wrapped around the entire building and took two hours just to get inside." According to Foley, that spurred him into finding a better way to get results to people quickly. "I did my research and found a better alternative to increase testing and reduce waiting times," says Taft. "The antigen test works in 15 minutes, which makes them amenable to point-of-care use. That's when I really got the idea of going out to our patients for the test so that they don't have to leave home." The tests are performed with a nasal swab, which then detects a viral protein in an actively infected person, giving accurate and fast results. Antigens are molecules capable of stimulating an immune response. The SARS-CoV-2 that causes COVID-19 has several known antigens including its nucleocapsid phosphoprotein and spike glycoprotein, which are the visible protrusions on its surface. Antigen tests reveal if a person is currently infected with a pathogen such as the SARS-CoV-2 virus. Once the infection is gone, the antigen disappears. Although antigen tests typically have lower sensitivity than a traditional PCR test, that detects the virus through its genetic material, they provide tests rapidly and are relatively cheaper to produce. "Getting this test to as many people as possible as fast as possible is essential," says Taft. "People need to know whether or not they need to stay home and if they're at risk of spreading the virus to others." The results are sent to patients via text message or email, giving individuals peace of mind quickly if they are not infected and allowing those with COVID-19 to quarantine themselves and those they have exposed. The test cost ranges from $100 to $150 for individuals, according to their website, depending on if testers would like to go to their tent location or take advantage of their mobile lab. While they currently do not accept insurance, most insurance companies will reimburse some or all of the cost of the test. You can reach the Texas Mobile Medical lab at (936) 333-3333 if you have COVID-19 symptoms and would like to schedule an appointment for testing. Texas Mobile Medical Lab website: http://www.texasmobilemedicallabs.com/
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