States clamoring for coronavirus tests in recent weeks have been talking about two different types, according to an NPR report. First, there’s a PCR test that detects the virus’ genetic material, so can confirm an active infection. And then there’s an antibody test, which looks at the body’s reaction to that infection, so is useful in identifying people who have been infected with the virus in the past.
Now, there’s a third kind of test under development to help fight COVID-19 that homes in on proteins that stud the virus’s outer surface; it, too, detects an active infection. Known as an antigen test, this one could offer a much easier and more widely available alternative for diagnosis than the PCR test, proponents say, though some other scientists remain concerned about the test’s reliability.