I Hear COVID Tests Are Hard To Get, Are We Being Too Picky?
Currently, the US is behind on testing in such large magnitudes that our case numbers are increasingly inaccurate since we simply aren’t counting the tests we can’t run. One major cause is that the gold standard of testing is a molecular based PCR test. This test requires swabs, tubes and reagents, and a lab. If you put all of those together you will find each with a bottleneck that has a multiplying effect. In most large cities, turnaround times for a PCR molecular test are 5-7 days. This is true for academic centers such as Stanford Hospital and large commercial labs such as Labcorp. Bill Gates commented in an interview last week that if you can’t get a test result in 48 hours, we as a country shouldn’t be paying for it since the data are too late to change our behaviors. Can we solve this problem? Yes, if we as a country, with medical leadership, can accept alternative testing that has less accuracy.
This New York Times article talks about how initially, the medical community was facing a shortage of N95 masks and the directive to the public was to not hoard, or not to wear masks at all. Later it became clear even cloth masks offer protection and that everyone doesn’t need an N95. The idea that if everyone can’t have an N95 was shortsighted in looking at the benefits of non-medical grade masks. This could be true for testing.
Leaving aside the systemic problems surrounding testing delays, the question is should we rely on the gold standard molecular test? The answer in March was yes, it is the most sensitive test in picking up the viral RNA particles. We, as a nation, and the medical community, hold high standards for all our testing and COVID testing is held to the same standards. But now, here we are months into a pandemic and the situation does not look good. We need more point-of-care testing so we can make real-time decisions. We can do that with antigen testing. This type of testing detects protein antigens from the virus particles; it is similar to the flu swab. It can be done on-site and results within minutes. The downside is, until now only one company Quidel
has an Emergency Use Authorization (EUA) from the FDA for its test and it has a lower sensitivity than the PCR test. For the flu, a negative test often was sent for a reflex PCR test; this could be the protocol for COVID as well.
From a surveillance standpoint, we know that more frequent testing and quick results are needed to mitigate the virus spread. So it may be time we adopt pooled testing (testing groups of people) frequently, with a less accurate (20% of the time) test to gain some traction. Medical offices, schools, businesses could do antigen testing as we try desperately to open our country. The longer we rely heavily on PCR testing with delayed results, we lose ground. We could be facing a situation where perfect is getting in the way of good enough, and right now we may need to accept less accurate widespread testing to get us out of the dire straits we are in.
(Prerana Sangani, MD, August 5, 2020)
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