Viral Test (RT-PCR, NAATs)
- A viral test checks samples to find out if you are currently infected with COVID-19. The time it takes to process these tests can vary.
- This test is considered the "gold standard" of testing
- A Viral test is most accurate in symptomatic persons or 5-7 days after known COVID-19 exposure
Antibody Test: test for past infection
- Antibody tests check your blood by looking for antibodies, which may tell you if you had a past infection with the virus that causes COVID-19.
- Antibodies are proteins that help fight off infections and can provide protection against getting that disease again (immunity). Antibodies are disease specific. For example, measles antibodies will protect you from getting measles if you are exposed to it again, but they will not protect you from getting mumps if you are exposed to mumps.
- Antibody tests should not be used to diagnose a current COVID-19 infections, except in instances in which viral testing is delayed. An antibody test may not show if you have a current COVID-19 infection because it can take 1-3 weeks after infection for our body to make antibodies.
Rapid Test / Antigen Test
- Antigen tests are commonly used in the diagnosis of respiratory pathogens, including influenza (flu) viruses and respiratory syncytial virus (RSV).
- Antigen tests are immunoassays that detect the presence of a specific viral antigen, which implies current viral infection.
- Antigen tests for SARS-CoV-2 are generally less sensitive than real-time reverse transcription polymerase chain reaction (RT-PCR) and other nucleic acid amplification tests (NAATs) for detecting the presence of viral nucleic acid.
- The specificity of antigen tests is generally as high as most NAATs, which means that false positive test results are unlikely when an antigen test is used according to the manufacturer's instructions, however, they still can occur.
- A rapid/antigen test is most accurate in symptomatic persons or people 7-10 days after exposure but still has a potential 20% false negative rate