The US Food and Drug Administration issued an emergency use authorization Wednesday for a new coronavirus antibody test developed at a Mount Sinai laboratory.
With this new test, there are now four coronavirus antibody tests that have been granted emergency use authorizations from the agency — and even more tests are expected to come through authorization, FDA Commissioner Dr. Stephen Hahn said during a live video interview with The Washington Post on Thursday.
"We expect more to come through the regular emergency use authorization," Hahn said. "We're working very actively."
The specifics: The Mount Sinai test, called the Covid-19 ELISA IgG Antibody Test, is authorized for use on blood serum or plasma specimens from patients suspected of prior infection with the coronavirus. It measures antibodies in those specimens that were generated as part of the patient's immune response to a novel coronavirus infection. The test can help determine whether someone had a prior infection or not.
A positive result from the Covid-19 ELISA IgG Antibody Test indicates that antibodies were detected and the patient potentially has been infected with the coronavirus. The test specifically measures IgG antibodies — and that's in contrast to the other tests that the FDA has authorized, which detect both IgG and IgM. Those tests can detect the class of antibodies called IgM antibodies, which are present earlier in infection.
"IgG antibodies develop later than IgM antibodies following infection, and generally do not begin to appear until 7 – 10 days after infection," according to an FDA fact sheet about the test. "When IgG antibodies are present it, often indicates a past infection but does not exclude recently infected patients who are still contagious."