But in recent months, both agencies have begun to concede that the testing methods that they’re using may not be as accurate as they would want them to be. They acknowledge that an increasing number of so-called positive test results are actually false positives.
On Nov. 3, the FDA released new guidelines for rapid antigen testing for COVID-19 that acknowledged a high likelihood of incorrect results. The guidelines stated that health care professionals “should expect some [false-positive] results to occur.” These would occur even when “very accurate” tests were used to screen large populations with “a low prevalence of infection.”
The FDA stated that the accuracy of rapid tests depends almost totally on the amount of COVID-19 in the population being tested, stating: “As disease prevalence decreases, the percent of test results that are false positives increase.”
As an example, the FDA stated that a test with 98 percent specificity would accurately screen “just over 80% in a population with 10% prevalence.” This would mean that 20 out of 100 positive results would be false positives.
The agency added that in a population with only a one percent prevalence, only 30 percent of those who test positive for the disease would actually have it....<<<Read The Full Article Here>>>...
