Types of COVID-19 Tests

Updated September 14, 2022

Refer to the summary chart for a quick comparison of PCR and antigen tests.

Follow the COVID-19 Public Health Flowchart if you test positive, have symptoms, or had a close contact exposure. 

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 (e.g., rapid at-home self-test) or molecular tests (e.g., PCR).

When to test

  • If you have COVID-19 symptoms such as a sore throat, cough, fever, congestion
  • If you were exposed to someone who has COVID-19 (and you have not tested positive in the past 90 days)
  • When returning to the University after academic breaks
  • Before and after a large social event or gathering
  • When you are asked to get tested by the University, the local health department, or your healthcare provider

How to get a test

Locations that offer PCR and antigen tests for personal use are listed on the University's COVID-19 testing webpage.

University units that utilize rapid antigen tests to support their operations can order them with a budget number from the UW Clean and Safe Storefront.

Which test to use

Consider these factors when choosing between a molecular PCR test and a rapid at-home antigen test.

PCR test  Antigen test
  • Best for early diagnosis of an infection
  • Can detect an infection in individuals with no symptoms and those who have COVID-19 but aren’t infectious
  • Use when you start developing COVID-19 symptoms
  • Use after a close contact exposure to someone with COVID-19
  • Screen prior to a social gathering, activity, venue entrance or event when you are symptom-free
  • If you need to confirm the results of an antigen test
  • For travel or venues/events requiring a negative PCR test result

 

  • Best for screening and rapidly identifying infectious individuals with symptoms and in high transmission settings
  • Use when returning to campus after academic breaks
  • If you have symptoms and cannot get access to timely PCR testing
  • If you have recovered from COVID-19 within the last 90 days and you have a new COVID-19 exposure and/or develop new COVID-19 symptoms
  • Rapid screening prior to a social gathering or activity when you are symptom-free (higher risk of false negative)
  • Use after a close contact exposure to someone with COVID-19

Do not get a PCR test if you had COVID-19 within the past 90 days (the test may be intermittently positive even after you are no longer infectious).

Antigen at-home self-tests may not be not accepted:

  • To meet travel testing requirements
  • For entry to some establishments or events requiring proof of a negative test
  • For healthcare facility workers (and trainees) in certain situations; check with your hospital or clinic’s employee health center.

    How to use a rapid antigen self-test

    The U.S. Food and Drug Administration (FDA) is advising people to perform repeat testing following a negative result on any at-home COVID-19 antigen test to reduce the risk an infection may be missed (false negative result).

    The FDA recommends repeat testing following a negative result, especially when you don't have COVID-19 symptoms. Repeat testing involves taking multiple antigen tests over a certain time period, such as every 48 hours. Follow instructions provided by the manufacturer to ensure an accurate result.

    Refer to the UW COVID-19 Public Health Flowchart for guidance on repeat testing in specific scenarios.

    About the tests

    Molecular PCR tests

    • 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.
    • PCR tests are highly sensitive, highly specific tests. Positive and negative results are highly reliable when used appropriately.
    • 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 are administered at a point-of-care site (e.g., health care provider, pharmacy, or public health testing site). Most molecular tests must be processed in a laboratory so it may take hours to days to get your results.
    • Antibody or serology tests are not viral tests and should not be used to diagnose a current infection.

    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 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. 
    • Antigen tests are less sensitive than PCR tests, but very accurate when a person has high viral levels (such as when they are experiencing symptoms and therefore likely to be contagious. However, antigen tests may miss low levels of virus, showing a "false negative" when a person isn't experiencing symptoms or are in the first few days of an infection. If your test result is negative, multiple tests may be necessary.
    • Positive results are especially reliable if you have symptoms and the COVID-19 Community Level is high.
    • False positives can occur when the COVID-19 Community Level is low.
    • 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).

    More information