![]() ![]() Multidisciplinary evaluation of the Abbott BinaxNOW COVID-19 Ag Card (BinaxNOW, a widely used rapid antigen test, included limit of detection, variant detection, test performance across different age-groups, and usability with self/caregiver-administration. While there has been significant progress in the development of rapid COVID-19 diagnostics, as the pandemic unfolds, new challenges have emerged, including whether these technologies can reliably detect the more infectious variants of concern and be viably deployed in non-clinical settings as “self-tests”. Scientific Reports volume 11, Article number: 14604 ( 2021) "That the limit of detection of these tests aren't necessarily in line with the viral load necessary to be infectious, you can be infectious in other specimen types, but not the infectious and specimen type you're actively testing.Multidisciplinary assessment of the Abbott BinaxNOW SARS-CoV-2 point-of-care antigen test in the context of emerging viral variants and self-administration "I think that these sorts of tests do have their place, but it's just really important to understand the caveats behind them," he said. When asked what the future holds for at-home antigen tests, Akana said declaring them "useless" would be "a step too far in one direction." Viloria Winnett said this doesn't mean that the accuracy of at-home tests has declined, but rather researchers are better able to understand their limitations. In that case, the antigen test wouldn't detect the virus. "What could feasibly happen is that someone could have a very low viral load in a nasal swab and not be detectable by the antigen tests, whereas they could have very high viral loads in saliva or throat or another specimen type - potentially infectious, viral loads." "We wanted to measure the viral load in each of those three specimen types, just to see if there's any differences in the dynamics there or how they evolve over time, and this has quite large implications for nasal antigen testing," Akana said. This doesn't mean the accuracy of at-home tests has declined, but rather researchers are better able to understand their limitations. "Then if we subsetted that to people who were infectious, meaning that they had high viral loads that are likely to be transmissible to other people, we found the performance was still fairly low - just above 60 percent," Viloria Winnett said. The authors of the study found that when looking at the performance of the test cross-sectionally, at-home antigen tests are only 44 percent accurate. "There are a lot of studies out there with kind of conflicting results, likely because the population that is actually doing the test makes a big difference for how well the tests performed." ![]() "We wanted to ask the question: How well do the rapid antigen tests detect people who are infected, and how well the rapid antigen tests detect people who are not just infected, but actually infectious and capable of transmitting the virus to other people?" Alexander Viloria Winnett, biology graduate student and study co-author, told Salon. Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter The Vulgar Scientist. Specifically, that the virus appears in a person's throat and saliva first, and then their nose. While they expected to observe similar virus levels in the three locations, their results told a different story that started to raise complexities and questions around at-home tests. In the new study, researchers at California Institute of Technology tracked viral loads in three places of the human body - nose, throat and mouth - over the course of a COVID infection. While it varies by brand, at-home tests generally work when a person swabs their own nostrils and then exposes the sample to a liquid chemical, which will then determine if they are positive or not by detecting the presence of the antigen being tested. The presence of antigens is an indicator that a patient has the SARS-CoV-2 virus, which causes COVID. At-home tests function by detecting the presence of substances called antigens that stimulate an immune response against COVID.
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