A: A positive antibody test result could mean you previously had a SARS-CoV-2 infection or COVID-19. A positive antibody test could also mean the test is detecting antibodies in your blood in response to your COVID-19 vaccine.
Test results from currently authorized SARS-CoV-2 antibody tests should not be used to evaluate a person's level of immunity or protection from COVID-19.
Molecular tests are generally more accurate and mostly processed in a laboratory, which takes longer; antigen tests—or “rapid tests”—are processed pretty much anywhere, including at home, in doctors' offices, or in pharmacies.
Antigen tests are still fairly accurate, particularly when someone is experiencing symptoms and their viral load is very high. However, they can be less accurate when someone has a lower viral load, such as in someone without symptoms. This could lead to false negative test results.
“Unlike the PCR test, the antigen test can only determine if you have an active virus in your body. The rapid test can't detect small amounts of the virus or asymptomatic cases as accurately as the PCR test can,” Heather said. The rapid test is less accurate and there is a greater chance for a false negative.