The PCR test is considered our “gold standard” because it’s highly accurate. But, sending off a sample to a lab takes time, requires special equipment, and typically takes at LEAST 24 hours to produce a result (we all know this is longer in the real world).
In order to tackle this pandemic, though, we need people to know if they are positive or negative as soon as possible. This way they can self-isolate, receive treatment, and inform close contacts. Because of this, several rapid COVID19 tests have been developed. These tests typically take 30 minutes to receive results (a max of 2 hours).
However, how accurate are rapid tests compared to the “gold standard”?
Turns out rapid molecular COVID19 tests are very accurate. If there were a group of 1000 people and 100 truly had COVID19, 105 people would get a positive test (10 false positives) and 895 would get a negative test (5 false negatives). The rapid Xpert Express (Cepheid Inc) test is better than the rapid ID NOW (Abbott Laboratories) test... That is if you ever have an option (which you probably don’t).
The authors also tested the accuracy of rapid antigen tests to potentially replace PCR tests. Antigen tests were definitely not as accurate as molecular tests. If there were 1000 people and 100 truly had COVID19, 61 people would have a positive test (5 false positives) and 940 people would have a negative (44 false negatives).
Translation: Rapid tests have the potential to replace PCR tests (especially those with a positive result). But, as always, we need more research.
Now, we know how fast science is developing. Since the publication of this article (August 26), two innovative tests have been released…
1. Abbott created a rapid nasal antigen test, in which the FDA has approved for emergency use. It’s called the BinaxNOW in which you get results within 15 minutes and it’s $5. The data in which Abbott turned to the FDA states this test is highly accurate (97.1% positive agreement) and 98.5% (negative% agreement). If all goes well, this should be ready for public use in October.
2. Yale created a saliva test called SaliviaDirect. This was also approved by the FDA for emergency use. It’s still being validated among players in the NBA. So far, this test is accurate, with 93% positive agreement and 97% negative agreement.
It’ll be exciting to see how these two tests (and many more) continue to develop.