FDA authorizes new test to detect past Covid-19 infections

The Food and Drug Administration on Friday issued an emergency authorization for a new test to detect Covid-19 infections -- one that stands apart from the hundreds already authorized. Unlike tests that detect bits of SARS-CoV-2 or antibodies to it, the new test, called T-Detect COVID, looks for signals of past infections in the body's adaptive immune system -- in particular, the T cells that help the body remember what its viral enemies look like. Developed by Seattle-based Adaptive Biotechnologies, it is the first test of its kind. Adaptive's approach involves mapping antigens to their matching receptors on the surface of T cells. They and other researchers had already shown that the cast of T cells floating around in an individual's blood reflects the diseases they've encountered, in many cases years later.