The CDC says antibody testing for coronavirus might be wrong up to half the time.
Also known as "serologic" tests, antibody tests are useful for looking broadly at the prevalence of the novel coronavirus in a given population, the CDC said. "Serologic test results should not be used to make decisions about grouping persons residing in or being admitted to congregate settings, such as schools, dormitories, or correctional facilities".
Aside from significantly infected places like food processing plants experiencing COVID-19 outbreaks, the CDC said, antibody tests are more likely to show false positives than false negatives. However, many experts believe they offer short-term immunity, says Dimitri Christakis, the director of the Center for Child Health, Behavior and Development at Seattle Children's Research Institute.
It is still unknown how long immunity from the virus lasts.
Even before the CDC's latest guidance, the accuracy of COVID-19 antibody tests has come under heavy scrutiny.
But many antibody test results may be incorrect, according to the CDC. However, most FDA-authorized tests have a positive predictive value somewhere between 80 percent and 100 percent. Since the EEOC has largely deferred to the CDC on this issue, employers who condition an employee's return to work on a positive test for antibodies may be subject to claims by both the individual and the EEOC.
The guidance further states that "additional data are needed before modifying public health recommendations based on [antibody] test results, including decisions on discontinuing physical distancing and using personal protective equipment". This low prevalence can lead to a higher percentage of false positives in a community. Thus, antibody test results may not definitively indicate the presence or absence of current or previous COVID-19 infection.