The Food and Drug Administration on Saturday announced emergency authorization for antigen tests, a new type of test developed by Quidel Corp. of San Diego.
The test looks for protein fragments associated with the virus. It can rapidly detect fragments of virus proteins in samples collected from swabs swiped inside the nasal cavity. It's less sensitive than the current PCR-based molecular tests, however, and comes with important limits on its use. Antigen tests can diagnose active infections by detecting the earliest toxic traces of the virus rather than genetic code of the virus itself.
The approved test can provide an accurate, automated result in 15 minutes. The antigen test is cheaper and easier to use and could "potentially scale to test millions of Americans per day." However, "antigen tests are very specific for the virus, but are not as sensitive as molecular PCR tests," the agency said. "This means that positive results from antigen tests are highly accurate, but there is a higher chance of false negatives, so negative results do not rule out infection." This test does require trained personnel, but can run only on Quidel's benchtop Sofia 2 analyzer.