April 17: We’ve gotten a lot of questions recently about antibody tests for COVID-19. Antibody tests, sometimes called “serology tests,” are blood tests that look for signs of an immune response to infection — in this case, immune molecules, or antibodies, specifically targeted to fighting the new coronavirus. An antibody test for COVID-19, if accurate, could indicate if you had previously been infected with the virus, even if you never had any symptoms.
For most illnesses, specific antibodies can be detected about four weeks post-infection. But we don’t know if antibodies to COVID-19 will follow the same timeline. We also aren’t sure how long COVID-19 antibodies last or if they confer immunity to reinfection.
“Antibody tests are being talked about a lot as a possible way to manage the pandemic in the future,” explains Dr. Shawn Ferullo, MIT Medical’s chief of student health. “If an individual with a positive antibody test is immune to COVID-19, they could go back to work or school and resume their normal activities without fear of becoming ill or infecting others. But South Korea is reporting some cases of repeat infection in individuals who have had the virus previously. So we still don’t know if a positive antibody test truly means immunity to the virus.”
Test accuracy is another concern. Beginning last month, the Food and Drug Administration (FDA) relaxed existing rules and began allowing companies to market COVID-19 antibody tests without requiring them to submit validation data proving that these tests gave accurate results. As a result, of the more than 100 COVID-19 antibody tests currently in use or soon to be in use, only a handful have actually been validated and approved by the FDA. And even tests that have been validated will be more or less accurate depending on the percentage of people in the population who have actually been exposed to the virus. When that percentage is relatively low, the likelihood of false positives is higher.
Despite these caveats, Ferullo believes that antibody testing will become a useful tool as the likelihood of exposure to COVID-19 increases. In fact, MIT Medical’s clinical laboratory is gearing up to be able to perform antibody tests in house.
In the meantime, however, we don’t recommend spending your own money to purchase antibody tests that are mentioned in social media or advertised online. Antibody testing is a decision you’ll eventually make in partnership with your healthcare provider. And by that time, we should know more about the accuracy of the test and what a positive result might mean in terms of possible sustained immunity to the virus.