Types of COVID-19 Tests

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Testing for current infection
Testing for past infection

Testing for current infection

Viral tests, sometimes called diagnostic tests, can detect if you have SARS-CoV-2 infection, the virus that causes COVID-19. There are two types of diagnostic tests: molecular and antigen.

If you have questions about which test is right for you, talk to a health care provider.

A positive viral COVID-19 test (molecular or antigen test) means the person who took the test has COVID-19 and can spread it to others. If you get a positive test result, you should stay home and away from others (isolate). You should follow the recommendations for staying at home even if you have a second test that is negative. Refer to If You Are Sick or Test Positive: COVID-19 for information on how long to stay home and how long to wear a mask around others.

It generally is not recommended that people get tested again after getting a positive result. However, those who work in health care and long-term care should follow testing recommendations specific to those settings.

Molecular tests

PCR, nucleic acid amplification tests (NAATs), and other molecular amplification tests detect the virus's genetic material.

• Molecular tests are the most accurate tests for detecting the virus that causes COVID-19.
• They can be used whether or not you have symptoms.
• A positive PCR, NAAT, or other molecular amplification test result means a person currently has COVID-19.
• They are given with a nasal swab or by taking a saliva sample.
  • Nasal swab: A nasal swab looks like a long Q-tip. It is inserted about two inches into your nose and swirled around for a few seconds. The swab is then removed and sent to a lab for testing. Nasal swabs are fast and accurate, and they’re a good option for most people. You may experience a tickling sensation while the swab is in your nose, and after it is removed, you might sneeze or have runny eyes for a moment or two. Health care providers are more likely to use nasopharyngeal swabs that go farther into your nasal cavity, and you may feel more discomfort than when doing an at-home nasal swab self-test.
  • Saliva test: Saliva tests are self-administered; this means that after you are shown how to perform the test, you’ll do it by yourself. You will spit several times into a funnel attached to a tube, and then screw on a cap to complete the test. Most people need 10-12 minutes to make enough spit to fill the tube. Saliva tests are more comfortable than nasal swabs and just as accurate, but they may not be a good option for those with low saliva production, such as very young children or those who have suffered a stroke.

Antigen tests

Antigen tests, sometimes called rapid tests, look for specific proteins on the surface of the virus.

• Antigen tests produce results more quickly than other tests.
• They are given with a nasal swab.
• A positive antigen test result means a person currently has COVID-19.
• Antigen tests are not as sensitive as molecular tests, no matter where they are performed (such as home, clinic, pharmacy). This means that you could have a negative test result even if you are infected with COVID-19.
• A negative antigen test may require follow-up testing to confirm the result, especially if you have symptoms or were in close contact to someone with COVID-19. Multiple negative antigen tests mean you can be more sure that you are not infected with the virus that causes COVID-19.
• If you tested negative on an antigen test at home (self-test), you should follow the manufacturer's instructions for repeat testing. Many of these tests are designed to be used doing multiple tests in a row, 24 to 48 hours apart. For more information, visit At-Home COVID-19 Antigen Tests-Take Steps to Reduce Your Risk of False Negative: FDA Safety Communication.

For more information on rapid tests that can be done at home, visit COVID-19 Self-Testing.

Testing for past infection

Antibody tests

Antibody tests, also called serology tests, look for antibodies in your blood that fight the virus that causes COVID-19. Antibodies can be in your blood from either past infection or vaccination.

• Test blood collected by a finger stick or blood draw.
• A positive antibody test means a person may have antibodies from getting COVID-19 in the past or from COVID-19 vaccine.

What antibody tests cannot tell us

• An antibody test cannot tell you if you currently have COVID-19. If you receive a negative antibody test, it does not mean you do not currently have COVID-19. A molecular or antigen test must be used to determine if you have COVID-19 right now.
• Antibody tests cannot tell if someone can get COVID-19 again. We do not know yet how long antibodies for the virus that causes COVID-19 last or the extent to which they protect people against new variants of the virus.
• Most antibody tests cannot distinguish between antibodies that developed through infection versus vaccination.

Learn more at FDA: COVID-19 Test Basics.