MARY LOUISE KELLY, HOST:
Last Thursday, minutes before we went on air, my phone rang - family emergency. I needed to get home to Georgia fast to help my parents. But they're in their 70s, and my dad is immunocompromised. And they were worried in this COVID era about letting me in the house, especially when I had just walked off a plane. This is how I came to spend last Friday trying to get a rapid coronavirus test. It turns out that in Atlanta, home of the CDC, that is surprisingly hard to do. Why? - months into this pandemic - a question I had plenty of time to ponder as I called clinic after clinic and one that I'm going to put now to my colleague on the science desk, NPR's Rob Stein.
Hey, Rob.
ROB STEIN, BYLINE: Hey, Mary Louise.
KELLY: So what I was searching for is called a rapid antigen test. You get results in 15 minutes, maybe even less, instead of the days and days that some people are waiting for results from genetic tests. Give us just the briefest of primers on how these rapid tests work.
STEIN: Yeah, sure. So yeah, the test most people have been getting are to search for genetic material from the virus collected by, you know, doing those swabs inside the nose. Antigen tests instead look for protein from the virus in those nose swab samples. They're a lot cheaper and easier to make and use than the genetic tests. And like you said, they produce results right on the spot within minutes, like those - you know, those flu and strep tests people are used to getting at their doctor's offices and at clinics.
KELLY: Yeah. And so why aren't they more widely available? - because I must have called or gone online at 15 clinics, maybe more. And I kept being told demand is through the roof; they're on back order; try us again next week.
STEIN: Well, basically, you know, it's a question of supply and demand. You know, so many people are getting infected in so many places right now that there just aren't enough tests available for everyone who wants or needs one. The companies that make these tests are ramping up to produce tens of millions of them. You know, that does take some time.
KELLY: Well, my story has a happy ending. I finally found a clinic that had them. I took the test. It was negative. How reliable, Rob, is that result?
STEIN: So the companies claim that these tests are very reliable, but not everyone is convinced. And that's because antigen tests tend, typically, to be less accurate than genetic tests, maybe missing as many as 2 out of every 10 people who are infected, especially if they're tested right after they get infected, before there's a lot of virus in their bodies. And that obviously could be a big problem. I talked to Jesse Papenburg at McGill University about this.
JESSE PAPENBURG: So if you're using this test to screen employees, as an example, and it turns out that you're missing 2 out of every 10 employees that are actually infected, well, that's just going to help promote spread in your work environment 'cause they're going to have a false sense of security that they were not infected.
STEIN: So the experts say even if someone tests negative on an antigen test, they really shouldn't let down their guard. And you know, it's not just false negatives that are a problem. These tests can also produce false positives. Now, that's not as dangerous, but it still can cause big problems, you know, forcing people to quarantine for two weeks, which means they could miss paychecks or school.
KELLY: Yeah. I mean, so they're not perfect, but I do keep thinking to that point about screening employees. We're trying to get adults back to work. We're trying to get kids back to school. There is such obvious value to being able to get test results almost immediately. Given all the downsides, how helpful is a test like this?
STEIN: Right. Like so - you know, like you said, no test is perfect. And even if the antigen tests aren't quite as accurate as, you know, we'd like them, some say the fact that they're so fast and so cheap and so easy to do makes them just much more practical to test people repeatedly. So if you miss an infected person on a Tuesday, you might spot them when you test them again on a Thursday. So overall, you may end up catching a lot more infected people, and you'll find out much quicker because you're not waiting days or even weeks for the results. There's also the possibility that these tests are just picking up people when they're the most infectious, which is really what you want the most. I talked to Michael Mina at Harvard about this.
MICHAEL MINA: With all of the limitations that perhaps an antigen test might have, they really shine in terms of their speed to get results and your ability to act on a positive case essentially at the same time that you're seeing the individual.
STEIN: You know, in fact, Mina hopes the FDA will authorize a new generation of simpler antigen tests that people could take at home like a home pregnancy test because even if they aren't quite as accurate, a quick, simple at-home test could go a long way towards helping control the spread of this virus.
KELLY: All right. Thank you, Rob.
STEIN: You're welcome. Anytime.
KELLY: Helping answer my questions there - NPR's Rob Stein. Transcript provided by NPR, Copyright NPR.
