In July of 2020 I wrote in Frequent, Fast, and Cheap is Better than Sensitive:
A number of firms have developed cheap, paper-strip tests for coronavirus that report results at-home in about 15 minutes but they have yet to be approved for use by the FDA because the FDA appears to be demanding that all tests reach accuracy levels similar to the PCR test. This is another deadly FDA mistake.
…The PCR tests can discover virus at significantly lower concentration levels than the cheap tests but that extra sensitivity doesn’t matter much in practice. Why not? First, at the lowest levels that the PCR test can detect, the person tested probably isn’t infectious. The cheap test is better at telling whether you are infectious than whether you are infected but the former is what we need to know to open schools and workplaces.
It’s great that other people including the NYTimes are now understanding the problem. Here is the excellent David Leonhardt in Where are the Tests?
Other experts are also criticizing the Biden administration for its failure to expand rapid testing. Even as President Biden has followed a Covid policy much better aligned with scientific evidence than Donald Trump’s, Biden has not broken through some of the bureaucratic rigidity that has hampered the U.S. virus response.
In the case of rapid tests, the F.D.A. has loosened its rules somewhat over the past year, allowing the sale of some antigen tests (which often cost about $12 each). But drugstores, Amazon and other sellers have now largely run out of them. I tried to buy rapid tests this weekend and couldn’t find any.
The F.D.A.’s process for approving rapid tests is “onerous” and “inappropriate,” Daniel Oran and Dr. Eric Topol of Scripps Research wrote in Stat News.
For the most part, the F.D.A. still uses the same cumbersome process for approving Covid tests that it uses for high-tech medical devices. To survive that process, the rapid tests must demonstrate that they are nearly as sensitive as P.C.R. tests, which they are not.
But rapid tests do not need to be so sensitive to be effective, experts point out. P.C.R. tests often identify small amounts of the Covid virus in people who had been infected weeks earlier and are no longer contagious. Rapid tests can miss these cases while still identifying about 98 percent of cases in which a person is infectious, according to Dr. Michael Mina, a Harvard epidemiologist who has been advocating for more testing
Identifying anywhere close to 98 percent of infectious cases would sharply curb Covid’s spread. An analysis in the journal Science Advances found that test frequency matters more for reducing Covid cases than test sensitivity.
As I said on twitter what makes the FDA’s failure to approve more rapid antigen tests especially galling is that some of the tests being sold cheaply in Europe are American tests just ones not approved in the United States. If it’s good enough for the Germans it’s good enough for me!