Antigen Testing Is Here. But There’s a Catch.

Quidel Corporation

For indispensable reporting on the coronavirus crisis and more, subscribe to Mother Jones’ newsletters.A couple of weeks ago Deborah Birx delivered a confusing Sunday morning answer to Chuck Todd about COVID-19 testing. She seemed to say that we were two or three weeks away from a big breakthrough in PCR testing, the current gold standard. But she also said that we had to have a breakthrough in antigen testing, and lots of companies were working on that. So . . . maybe she was actually referring to a breakthrough in antigen testing? Maybe. In any case, it looks like we’re getting it:

The Food and Drug Administration has granted emergency-use authorization to Quidel Corp. for the first antigen test for the Covid-19 virus—a step that could escalate the nation’s ability to test for the disease. It is believed to be generally faster, cheaper and easier to manufacture than most current diagnostics.
….San Diego-based Quidel, which specializes in tests for flu, strep and other infectious diseases, already has placed about 36,000 test-analyzer instruments around the U.S. in places like hospital labs, emergency departments and doctors’ offices. “We are ramping up manufacturing to go from 200,000 tests next week (week of May 11) to more than a million a week within several weeks,” said Douglas Bryant, Quidel’s chief executive.

A million tests a week is still a small fraction of what we need, but if we can ramp up to a million, we can ramp up to ten million. And antigen testing is faster and more convenient than PCR testing: it still requires a nasal swab, but results are returned in less than 30 minutes and don’t require any special expertise to interpret.
So: good news, right? Not so fast. The Quidel test, it turns out, is only about 85-90 percent accurate, and that’s mostly because it returns a lot of false negatives. This means that if you test negative—as the vast majority of people do—you need to follow up with a traditional PCR test to be sure. It’s still a useful test, but until it gets better it’s not all that useful.