Medically reviewed by Susan Kerrigan, MD and Marianne Madsen
Right now, a positive COVID-19 antibody test result could be wrong 50% of the time.
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.
These tests, also known as serologic tests, are meant to detect antibodies people develop after becoming infected with the coronavirus. Extensive, accurate testing could be vital in determining how rampant the spread of COVID-19 is and the true death rate of the disease.
However, per the CDC, the tests are currently not accurate enough to be factored into decision-making about allowing large groups to gather–namely in schools, dormitories or correctional facilities.
According to the CDC, it takes between one and three weeks after someone develops coronavirus symptoms for antibodies to become detectable. When the antibodies are detectable, the likelihood of being infectious is “greatly decreased,” and there is “some degree of immunity.”
The CDC further asserts that serologic test results should not be used to make decisions about grouping people in residences or admitting them to congregate in settings such as schools, dormitories, or correctional facilities. Serologic test results also should not be used to make decisions about returning people to the workplace.
A false positive will lead someone to believe they have been infected when in fact they have not been. “It cannot be assumed that individuals with truly positive antibody test results are protected from future infection,” the CDC says in the updated guidelines. “Serologic testing should not be used to determine immune status in individuals until the presence, durability, and duration of immunity is established.”
But research on COVID-19 and the antibodies produced in response to infection is still ongoing, which is why the CDC says people who test positive for antibodies should not assume they’re immune from getting the novel coronavirus going forward. In addition to many people reporting inaccurate results, many of the hundreds of antibody tests on the market have advertised claims “that make no sense,” according to CBS News medical contributor Dr. David Agus. “So the tests that we have now on the market … don’t tell you individually whether you have the neutralizing antibodies, whether you have the antibodies that can prevent you from getting an infection again,” he said.
According to the CDC, less than half of those testing positive will truly have antibodies, and everyone should continue to practice preventative measures including social distancing, proper hygiene, and wearing personal protective equipment regardless of whether or not they have tested positive for antibodies or have had the coronavirus.