The New York Times
Getting an antibody test to see if you had Covid-19 months ago is pointless, according to guidelines issued this week by a major medical society. Many tests are inaccurate, some look for the wrong antibodies and even the right antibodies fade away, said experts at the Infectious Diseases Society of America, which issued the new guidelines. Because current tests cannot determine if someone is immune, the society said, they “cannot inform decisions to discontinue physical distancing or lessen the use of personal protective equipment.” Antibody testing generally should be used only for population surveys, not for diagnosing illness in individuals, the panel said. But its guidelines described two situations in which antibody testing could be used when the normal diagnostic tests for the virus — called PCR tests — failed or were likely to fail.