An illustration shows spiky antigens studding the virus’s outer coat. Tests under development that look for these antigens might be faster than PCR tests for diagnosing COVID-19, proponents say. But the tests might still need PCR-test confirmation.

An illustration shows spiky antigens studding the virus’s outer coat. Tests under development that look for these antigens might be faster than PCR tests for diagnosing COVID-19, proponents say. But the tests might still need PCR-test confirmation.