COVID tests weren't designed for this

People are turning to testing for asymptomatic check-ins that can give them peace of mind before a big event, or even give them the go-ahead to travel overseas. But a lot of these screening tests were initially designed to diagnose people who were already sick—and the tests’ performance won’t necessarily hold when they’re being repeatedly used on symptom-free people at home.

Part of the problem can be traced back to how the United States’ thinking on testing has evolved. Early on in the pandemic, regulatory agencies like the FDA prioritized tests for symptomatic patients; the agency has since noticeably shifted its stance, authorizing dozens of tests that can now be taken at home. But there are still some relics that have influenced how the tests have, and have not, been evaluated for use.

Tests such as the Abbott BinaxNOW, for example, were first studied as a rapid diagnostic that people could take shortly after their symptoms first appeared. It can now be used as a screener, when it is serially administered at home to asymptomatic people (which is why the tests are sold in packs of two). But to nab that expanded authorization from the FDA, the company didn’t have to submit any data on the test’s performance when it was serially administered at home, or how well it worked in asymptomatic people. Instead, the FDA has been green-lighting serial tests based on how well their results match up to PCR results in symptomatic people. They just have to detect 80 percent of the infections that the super-sensitive molecular tests do, in a clinical setting.