Most tests to determine if somebody has already been infected with COVID-19 check for antibodies, but a new study in Italy found that those tests are much less accurate than a new type that looks for a type of immune cell called a T cell. Researchers from the U.S., Britain, and Italy conducted blood tests on 70 people in Vo, Italy, who had been infected with the new coronavirus in the past two months. With the antibody screen, 16 people tested negative, a false negative rate of 23 percent; with T cells, there were only two false negatives, a rate of 3 percent, CNN reports.
The researchers also studied 2,200 people who had tested negative for COVID-19, and only 45 of them were found to have been infected with the T cell test. Dr. Lance Baldo, a coauthor of the unpublished study, said many of those 45 people likely had COVID-19 at some point but did not realize it. The company that makes the test in question, Adaptive Biotechnologies, plans to seek FDA emergency use authorization for a commercial vision of its test in late November.
The body's immune response to a virus like COVID-19 is "like a military operation, where you have different components," former FDA commissioner Dr. Andrew von Eschenbach tells CNN. "The Navy lands on the shore, the Air Force attacks from on high, the Army comes in with artillery. ... When something tries to invade us, the fight our body launches is extremely sophisticated and complicated." The source of the antibodies dies off in a few months, but T cells have been known to remain in the body for years.