The US Food and Drug Administration on Wednesday issued emergency use authorizations for two new coronavirus antibody tests, which are able to detect past infections after people have recovered.
A total of three tests are now authorized by the agency, which determined that the benefits of using the quickly-designed tests during the pandemic outweigh the risks – such as false negatives or false positives.
The tests, which use blood samples instead of a swab, are limited to use in authorized laboratories. Instead of looking for traces of the virus, they look for our body’s response to the virus: antibodies.
The FDA, though, is warning that the tests could lead to false negatives, since antibodies aren’t present at the earliest stages of infection.
“A negative result may occur if you are tested early in your illness and your body hasn’t had time to produce antibodies to infection,” the agency said in fact sheets published Wednesday.
While the tests may miss some recent infections, experts say they’re useful to understand how widespread the coronavirus really is – since they should be able to detect past infections, even if people had few or no symptoms.
It’s unclear how long immunity might last after someone recovers from Covid-19, but the antibody tests could also offer insight into who may be protected against re-infection.
In a series of tweets announcing the new authorizations, FDA Commissioner Dr. Stephen Hahn said: “Serology tests can play a critical role in fighting #COVID19 by helping health care professionals identify people who may have overcome #COVID19 & developed an immune response.”
The new tests come from Chembio Diagnostic Systems and Ortho Clinical Diagnostics, and they join a test authorized in early April from the company Cellex.
The nation’s top infectious disease expert, Dr. Anthony Fauci, hinted at the new authorizations last week.
"Within a period of a week or so, we're going to have a rather large number of tests that are available," he said on CNN's New Day Friday morning.