April 2, 2020 / Elizabeth Weise, USA TODAY
The FDA has authorized the first test for coronavirus that measures antibodies in the blood. Such tests could identify people who have recovered from COVID-19, key for knowing who’s immune and developing a vaccine.
Cellex Inc. of Research Triangle Park, North Carolina received an emergency use authorization for its test Thursday from the Food and Drug Administration. It uses blood drawn from a vein to measure antibodies to the SARS-CoV-2 virus that causes COVID-19. 
It is the first of an expected flood of such tests as companies race to develop them. Antibody tests are already being used in several countries, including China, South Korea and Singapore.
“Antibody positivity likely means a person has recovered and can’t be reinfected. This test will be extremely valuable, especially for healthcare workers,” said Alan Wu, a professor of laboratory medicine at the University of California, San Francisco and chief of the clinical chemistry and toxicology laboratories at Zuckerberg San Francisco General Hospital. His team is testing several possible COVID-19 blood tests.