After a gush of bogus coronavirus blood tests, the US Food and Drug Administration announced Monday that test makers must submit data within 10 days showing that their tests actually work—or risk getting purged from the market.
The new requirement updates a lax policy the FDA announced March 16, which prioritized providing “regulatory flexibility” to allow these blood tests—aka serology tests—to hit the market quickly during the pandemic. That flexibility came at the expense of normal scientific vetting that ensures those tests meet standards for accuracy and reliability.
“In mid-March, it was critical for the FDA to provide regulatory flexibility for serology test developers, given the nature of this public health emergency… However, flexibility never meant we would allow fraud,” the FDA wrote in a policy update Monday. “We unfortunately see unscrupulous actors marketing fraudulent test kits and using the pandemic as an opportunity to take advantage of Americans anxiety.”
The serology tests are intended to detect antibodies against the new coronavirus, SARS-CoV-2. Antibodies are Y-shaped proteins that can circulate in the blood to recognize specific germs that the immune system has previously fought off. Antibodies generally do this by homing in on signature features of a germ, such as the spiky proteins that jut out of the SARS-CoV-2. If the germ shows up again, those antibodies—made by specialized immune cells—can quickly recognize the invader and trigger an immune response to try to prevent reinfection.
Thus, the presence of antibodies in a persons blood only tells if the immune system has encountered the germ in the past—its not used to diagnose new cases of COVID-19, the disease caused by SARS-CoV-2. There are separate diagnostic tests for that, which generally work by detecting genetic material from the virus itself.
Testing people for past infections is mainly helpful on a population level. It can help public health researchers to understand how far the virus has spread, what proportion of infected people have asymptomatic or extremely mild cases, and the diseases true fatality rate (which is generally calculated by the number of deaths among the number of infected people who recover.)
For better-understood diseases, antibody tests can also help determine if a person is likely to be immune to reinfection. That is, for some diseases, our immune systems can make brawny antibodies that can completely prevent reinfection. So, if a person tests positive for antibodies to a specific germ, that may mean theyre protected against that disease. But not all antibodies are so protective. They can also be weak or wane over time—potentially within months. For now, we dont know enough about our own immune responses to SARS-CoV-2 to know if antibodies against the virus are protective and, if so, for how long. That means, if someone tests positive for SARS-CoV-2 antibodies, they may still be able to get COVID-19.