Coronavirus antibody tests could be wrong up to half the time: CDC

Antibody tests for COVID-19 — used to determine if people have been infected in the past with the deadly illness — might be wrong up to half the time, the Centers for Disease Control and Prevention announced.

The antibody tests, often called serologic tests, look for evidence of an immune response to infection, but are not accurate enough to use in making important policy decisions, the CDC said in new guidance.

“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,” the federal agency said.

“Serologic test results should not be used to make decisions about returning persons to the workplace,” it added.

The tests “can play an important role in understanding the virus’s epidemiology in the general population and identifying groups at higher risk for infection,” the CDC said.

The tests “do not typically replace direct detection methods as the primary tool for diagnosing an active SARS-CoV-2 infection, but they do have several important applications in monitoring and responding to the COVID-19 pandemic,” it continued.

“Although serologic tests should not be used at this time to determine if an individual is immune, these tests can help determine the proportion of a population previously infected with SARS-CoV-2 and provide information about populations that may be immune and potentially protected.”

Health officials or health care providers who use the tests must use the most accurate ones they can find and may need to test people twice, the CDC said.

“In most of the country, including areas that have been heavily impacted, the prevalence of SARS-CoV-2 antibody is expected to be low, ranging from less than 5% to 25%, so that testing at this point might result in relatively more false positive results and fewer false-negative results,” it added.