Here’s the key: What is more important than a perfect test is one that turns positive during the time period in which an individual can spread the virus to others—and that’s, purportedly, what these cheap tests do well. Generally, disease transmission in COVID-19 is believed to begin early—several days before one becomes symptomatic. Viral load levels peak early and then they gradually decline, with an individual unlikely to be infectious approximately eight to 10 days after showing symptoms.
Though efficacy needs to be better proven, these antigen tests are efficient at detecting virus at high viral loads. When they are used frequently during this period of infectivity, Mina believes their sensitivity and performance would far exceed that of a single PCR test. At any rate, Mina and his colleagues have demonstrated in their statistical models thatpublic health surveillance depends much more on frequency of testing and rapid reporting of results than it does on the comparative sensitivity of the tests themselves.‘Instant Coffee’ COVID-19 Tests Could Be the Answer to Reopening the U.S. https://www.scientificamerican.com/article/instant-coffee-covid-19-tests-could-be-the-answer-to-reopening-the-u-s/
Comparing PCR testing, the nasal swab vs. antigen testing which is much less expensive and produces rapid results, these tests are both commonly offered in Oklahoma. The difference in the tests is the sensitivity in the tests. The big difference between PCR and antigen is overall antigen tests are less sensitive. You can have confidence in a rapid antigen test if it says you are positive, but let’s say you are symptomatic and you go in for a test because you think you may have COVID-19 and they do an antigen test and you get a negative test — you should remember that 20% or more of antigen tests come back as negative. So there is high predictive value for positive.OU Medicine chief explains why you should trust a positive result from a rapid COVID-19 test https://oklahoman.com/article/5669756/ou-medicine-chief-explains-why-you-should-trust-a-positive-result-from-a-rapid-covid-19-test