Types of COVID-19 viral tests
COVID-19 viral tests are diagnostic tests that can tell you whether you are currently infected with the virus that causes COVID-19 at the time of the test. COVID-19 viral diagnostic tests can be either antigen tests or molecular tests.
You may need to take a viral test:
- If you have COVID-19 symptoms;
- If you were exposed to someone who has COVID -19;
- When you are referred to get tested by your healthcare provider, local health department, school, or work;
- Before or after travel; or
- For entrance to a venue, event, or activity.
Refer to the When Do I Use It? section below for additional details.
COVID-19 antigen tests
COVID-19 antigen tests look for the presence of specific SARS-CoV-2 virus protein structures (antigens) in a sample. Antigen tests can be less expensive than molecular tests and can give you rapid results- typically in less than 30 minutes.
Antigen tests are helpful in providing fast, generally reliable results when you have COVID-19 symptoms. However, antigen tests are less sensitive than molecular tests; they may miss an early infection when there are low levels of virus in the body, also known as a false negative test result.
Antigen tests can be administered in point-of-care settings (provided and interpreted by health care providers, testing facilities, pharmacies etc.), or sold online and at retail locations and administered at home (in self-test form).
COVID-19 molecular tests
COVID-19 molecular tests look for the presence of SARS-CoV-2 virus genetic material (nucleic acid or RNA fragments) in a sample. Molecular tests include PCR tests (reverse transcription polymerase chain reaction or RT-PCR), which are reliably accurate.
Molecular tests are more sensitive than an antigen tests; they can detect much smaller amounts of virus in the body, and therefore detect an infection earlier and can continue to detect remnants of the viral RNA in the body well after the infection has resolved.
Most molecular tests (e.g., PCR tests) are administered at a point-of-care site (e.g., health care provider, pharmacy, public health testing site, private lab). Most molecular tests must be processed in a laboratory so it may take hours to days to get your results.
Husky Coronavirus Testing, a UW voluntary research study, provides lab-processed PCR tests.
Antibody or serology tests are not viral tests and should not be used to diagnose a current infection.
Read the Public Health – Seattle & King County blog that further explains differences between rapid antigen tests and molecular PCR tests.