Thread by @katherineefoley

Last week, the US Capitol had a huge problem which has since been overshadowed: @US_FDA flagged that the @Curative #COVID19 PCR tests it had been to screen entrants had more false negatives than expected. Here's what offices can learn to reopen safely: 1/x qz.com/work/1954140/w…

2/x The backstory: @Curative's #COVID19 PCR tests work like many others; they detect SARS-CoV-2 genetic material in quick swab. It returns results in 12 hours—which is fast for PCR! @US_FDA granted Curative an EUA in April; it also provides tests for big cities across the US.

3/x @US_FDA's warning last Mon. says tests have higher rate of false negatives, meaning someone could be told they don't have #COVID19 but they actually do. The risks are 1) that person misses out on treatment and 2) that person spreads the virus to others
fda.gov/medical-device…

4/x It's not ENTIRELY surprising that this warning came out; if you look at Curative's EUA, the sample size they used for sensitivity/specificity wasn't very big huge. But also, that's pretty common for EUA Covid-19 tests; FDA was rushing to get tests out fda.gov/media/137089/d…

(4.5 Quick refresher from @timmcdonnell and @AShendruk: Sensitivity = correctly ID'ing who is infected; specificity = correctly ID'ing who ISN'T infected.
qz.com/1941258/how-to…)

5/x Aside from that, though, there was the problem with choosing to use a PCR test for workplace reentry to begin with. PCR tests were never meant to find Covid-19 patients among asymptomatic individuals; they're a diagnostic tool. @Curative's EUA makes this clear:

6/x Generally, PCR is regarded as the gold standard in Covid-19 diagnostics. But they're still an inferior choice for reopening a workspace.
1) They're expensive (~$100 each)
2) They take a while (12 hours = a person walking around all day)
3) They STILL have false negatives!

7/x As @Michael_Hochman has told me before (and reminded me for this story), getting a negative #COVID19 PCR test doesn't mean much if you know/suspect you've been exposed. You'd still need to quarantine, even if you never develop symptoms qz.com/1905604/should…

8/x PCR tests are more likely to be accurate the longer you wait after an exposure; at least 2 days, ideally 5. A positive test initiates a contact tracing chain, which is important to contain the spread of it. So they're not great for an office reopening strategy.

9/x Here's where rapid antigen tests could be a better solution. They've got a smaller window for high sensitivity; positive tests show up within a day/2 of symptoms. however:
1) They're cheaper ($5)
2) Fast, actionable results (15 minutes)

(9.5/x Btw there's an excellent graphic in here about the windows for certain kinds of testing nature.com/articles/d4158…)

10/x Antigen tests look for proteins around the virus; they're much easier to administer over and over again cheaply, and you can act on the results almost immediately, @michaelmina_lab told me. (He's advocated for these for a while: time.com/5912705/covid-…)

11/11 The thing I've seen covering the pandemic in the US again and again is that ppl think we can rely on just one tool—like a PCR test—with no nuanced strategy. That doesn't work. Any strategy to reopen spaces cant just borrow from hospital diagnostics. qz.com/work/1954140/w…