May 27, 2020 | By Li Cohen | CBS News | Source |
“New guidance from the Centers for Disease Control and Prevention warns that coronavirus antibody test results may still be too inaccurate to be reliably used to determine coronavirus-related policy. In addition, not enough is known about what exactly the presence of antibodies indicates in terms of future immunity, the CDC said on its website.
These tests, also known as serologic tests, are meant to detect antibodies people develop after becoming infected with the coronavirus. Widespread, accurate testing could be vital in determining how rampant the spread of COVID-19 is and the true death rate of the disease.
But the CDC says the tests are currently not accurate enough to be be factored into decision-making about about allowing large groups to gather, namely in schools, dormitories or correctional facilities.
“Serologic test results should not be used to make decisions about returning persons to the workplace,” the CDC added on its site.”
“…. The CDC also explained why testing may not give accurate results for many individuals.
“For example, in a population where the prevalence is 5%, a test with 90% sensitivity and 95% specificity will yield a positive predictive value of 49%,” the CDC said on its website. “In other words, less than half of those testing positive will truly have antibodies. Alternatively, the same test in a population with an antibody prevalence exceeding 52% will yield a positive predictive greater than 95%, meaning that less than one in 20 people testing positive will have a false positive test result.”
Even before the CDC’s latest guidance, the accuracy of COVID-19 antibody tests has come under heavy scrutiny.”