Rapid COVID-19 Tests Can Be Useful – But There Are Far Too Few To Put a Dent in the Pandemic
Yves here. I am sure readers will have more to say about this article on rapid Covid tests, as in antigen tests, which require a non-traumatic swab of both nostrils (the PCR tests are the ones that sample the back of your throat via your nose). Two additional points: the antigen tests have high accuracy in symptomatic patients, but generate a lot of false positives otherwise. And they aren’t cheap. Here in Alabama, the charge at the urgent care center (which did test and process the results pronto) was $185, which they said my insurer would pay….but my reading of the fine print on Cigna’s site said I had to be recently exposed. Fortunately, that time, I had just been in the ER for four hours, and mistakenly spent about 20 minutes in the Covid section (no signs or partitions whatsoever; it was a guard who noticed and shooed me out). The bathrooms were also off the Covid area. So while I am presumably OK for this one test were Cigna to challenge me, how much tolerance would they have for paying for more tests, even though the level of uncontrolled spread in the US means that anyone who isn’t a hermit having everything delivered to them can contend that they’ve been exposed?
So medical industry price gouging would also impede widespread rapid testing, even if they were available. The odds of something as cheap and easy as a home pregnancy test or ketone strips coming soon seems remote.
By Bonnie LaFleur, Professor of Biostatistics, University of Arizona and Katherine Ellingson, Assistant Professor of Epidemiology and Biostatistics, University of Arizona. Originally published at The Conversation
Since September, the Food and Drug Administration has approved seven COVID-19 tests that yield results in 30 minutes or less, offering hope for vast improvements in test access and efficiency throughout the U.S. Most of these are antigen tests that look for viral proteins and can be processed on portable machines or cards.
This calls into question whether the current influx of rapid tests can actually slow the spread of COVID-19.
In some targeted applications – and if people take other precautions including mask wearing and social distancing – rapid tests can be a valuable tool. But the current state of availability and accuracy of these tests greatly limit how effective they are at slowing the spread of the virus in communities.
For rapid tests to effectively limit spread of the coronavirus, experts suggest that they must be conducted with high frequency– you might miss some cases, but if everyone were getting tested all the time, you would catch a lot of cases too. But even frequent testing is not a panacea. It’s only one part of an approach that must also include social distancing, mask wearing and other precautions.
A highly publicized example of how a rapid testing strategy can go wrong occurred when President Trump and many in his inner circle contracted COVID-19, likely stemming from a single superspreading event. Everyone was reportedly getting daily rapid tests, but they were largely ignoring other measures like face masks and social distancing. It is likely that someone was infected and asymptomatic, tested negative, and then started the outbreak.
Widespread, Repeat Testing
Detecting pre-symptomatic and asymptomatic individuals who are infectious is critical to controlling the coronavirus. Rapid tests can do this, but only if people are screened repeatedly on a schedule – much as what has been happening in some professional and intercollegiate sports.
Researchers have estimated that the U.S. would need to perform at least 20 million rapid tests per day to drive down infections. The 150 million rapid tests ordered by the government in late August were earmarked for high-risk populations, but would barely cover one week for the population at large. And don’t forget that logistic capabilities, compliance to frequent testing and the infrastructure to act quickly on results all need to happen as well.
Rapid tests can be effective in highly controlled settings where people are tested frequently and other mitigation measures are in place. Look to the success of the NBA bubble as proof. But in other settings where isolation, mask wearing and social distancing are hard to implement or not followed – like nursing homes or the White House – rapid tests have not kept the virus at bay.
Current testing capacity is nowhere near the hundreds of millions of tests per week required to protect the general population. To date, the promise of cheap and convenient COVID-19 tests being the sole means of controlling disease transmission has not been realized.