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

Nucleic acid amplification tests (NAATs), including PCR, detect the virus's genetic material.

• Molecular tests are the most accurate tests for detecting the virus that causes COVID-19. Both molecular and antigen tests (rapid tests) are very accurate and reliable for positive results. However, antigen tests are less reliable than molecular tests for negative results.
• They can be used whether or not you have symptoms.
• A positive PCR or other molecular amplification test result means a person currently has COVID-19.
• Molecular tests are performed by collecting a nasal swab or 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.
  • Saliva test: Saliva tests are self-administered; this means that after you are shown how to perform the test, you will do it by yourself. You will spit multiple times into a funnel attached to a tube, and then screw on a cap to complete the test. Most people need 10 to 12 minutes to make enough spit to fill the tube. Saliva tests 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 faster than other tests.
• The test sample is collected with a nasal swab.
• A positive test result means you currently have COVID-19 and do not need to test again.
• Antigen tests are not as sensitive as molecular tests, no matter where they are performed, such as at home, a clinic, or pharmacy. This means that you could have a negative test result even if you are infected with COVID-19.
• To be confident you do not have COVID-19, the CDC and FDA currently recommend serial testing, which means taking more than one antigen test if your first test is negative. If you have symptoms of COVID-19 and get a negative result, you should test again in 48 hours. If you do not have symptoms and spent time close to someone with COVID-19, you should have three negative antigen tests spaced 48 hours apart. A single PCR test can also be used to confirm an antigen test result. Visit CDC: COVID-19 Testing: What You Need to Know for the CDC and FDA antigen testing recommendations.

For more information on rapid tests that can be done at home, visit COVID-19 Self-Testing and Frequently Asked Questions About At-Home COVID-19 Tests.

Testing for a new COVID-19 infection if infected in the last 90 days

If you have had COVID-19 or a positive test result in the past 90 days, you should use an antigen test. You should test right away if you have symptoms of COVID-19 because you can get re-infected with the virus. For the CDC's specific testing recommendations for people who have had COVID-19 in the last 90 days, including testing if you do not have symptoms, refer to COVID-19 Testing: What You Need to Know.

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.

• Antibody tests use 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 your antibody test is negative, it does not mean you currently do not 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.