Comment: At this point, rapid antigen tests better than PCR

They’re quicker and can be more useful in situations, including testing in schools to keep them open.

By Ezekiel Emanuel, David Michaels, Rick Bright and Luciana Borio / Special To The Washington Post

Everything about testing for covid-19 appears overly complicated. It is no wonder Americans are confused; and getting angry. So here’s a way to simplify our testing game plan: Let’s sideline polymerase chain reaction (PCR) tests in favor of rapid antigen tests.

For most of the pandemic, Americans have been told PCR testing is the gold standard. But in most situations, it is not. Ideally, coronavirus test results should guide actions related to isolation, travel, social interactions or even when to seek treatment options. PCR testing is less than useful to do any of these for two reasons.

First, most PCR tests have a long lag between sample collection and test result. A result that takes longer than 18 hours is of little use for people trying to make decisions. Indeed, between taking the test and receiving the result, a person could become infected or turn positive, especially with the highly infectious omicron variant. Second, PCR tests can detect viral particles many days after infection, which might not indicate contagiousness. From an individual standpoint, there is no good reason to get a PCR test at this stage of a widespread pandemic.

Some airlines or countries might require a test within 72 hours of flight departure or entry into a country. In this case, PCR tests are acceptable, as a negative PCR test taken 24 hours before flight is useful information. But a positive PCR test could be misleading and overly restrictive because a person could be clear of the virus weeks before taking the test.

Meanwhile, rapid antigen tests have four advantages. First, if you have covid-19 symptoms such as fatigue, fever, cough, or loss of smell and taste, an antigen test can quickly confirm the diagnosis. For those at high risk of hospitalization or other serious outcomes, including the immunocompromised, elderly and unvaccinated, that means they can immediately seek medical advice about treatment options such as the monoclonal antibody sotrovimab, the intravenous antiviral remdesivir or the newly authorized oral antiviral treatments, Paxlovid or molnupiravir.

A person with a high-risk exposure — in close proximity to someone infected with the virus — should consider testing, too, but the Centers for Disease Control and Prevention recommends waiting until symptoms occur or five days after the exposure, as testing too early is less likely to detect an infection.

Second, antigen tests can help inform someone with covid-19 whether they should end isolation. The CDC currently recommends that people with covid-19 isolate for five days after testing positive and wear a mask when around others for an additional five days. But antigen tests can help provide reassurance to people on whether it is safe to go back to work or other situations where they will be in close contact with others.

Of course, antigen tests can miss an infection and produce false negatives. So those who end isolation should still wear high-quality face coverings — such as NIOSH-approved N95, KN95 or KF94 masks — when interacting with others for a total of 10 days after a case of covid begins.

Third, antigen tests can help assure people that it is safe to visit someone who is at high risk of serious problems because of covid-19. For example, it is entirely appropriate for anyone to be tested before attending a family gathering with an elderly person or someone who is immunocompromised because they are undergoing cancer therapy or taking immunosuppressants. A negative test result does not completely rule out infection, but it does significantly reduce the odds and can guide appropriate action.

Finally, antigen tests can be used for screening in schools. For instance, if performed on a regular cadence — three times a week or so — they can detect early infection and, with appropriate action, minimize transmission. They can also be used for a “test-to-stay” strategy. If one student tests positive, then the other exposed students in the class who test negative remain in class.

Under this game plan, there is no need for someone without symptoms or who has had a high-risk exposure to take a PCR test, unless they can get a very rapid result. Shifting to reliance on rapid antigen tests will help slow transmission during this pandemic. It should also ease the confusion and concerns of Americans about getting a coronavirus test.

Ezekiel Emanuel is a medical ethicist and professor at the University of Pennsylvania. David Michaels is a former administrator of the Occupational Safety and Health Administration and professor at the George Washington University School of Public Health. Rick Bright, chief executive of The Rockefeller Foundation Pandemic Prevention Institute, was director of the Biomedical Advanced Research and Development Authority. Luciana Borio is a senior fellow for global health at the Council on Foreign Relations andformer acting chief scientist at the Food and Drug Administration. They all served as members of the Covid-19 Advisory Board for the Biden-Harris transition.

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