COVID-19: The Basics of Testing

By Jane Farrell

You’ve heard a lot about coronavirus testing recently. If you think you have coronavirus disease 2019 (COVID-19) and need a test, contact your health care provider immediately.

Here, the federal Food and Drug Administration (FDA) outlines the different types of tests and the steps involved.

A diagnostic test can show if you have an active coronavirus infection and should take steps to quarantine or isolate yourself from others. Currently there are two types of diagnostic tests – molecular (RT-PCR) tests that detect the virus’s genetic material, and antigen tests that detect specific proteins on the surface of the virus.

The molecular test is also known as a viral test or nucleic acid amplification test (NAAT). A sample is taken via nose or throat swab or, less frequently, saliva. Results may be available in as little as one day or up to a week. The FDA says that the test is highly accurate and does not need to be repeated. It diagnoses an active coronavirus infection, but it cannot tell whether you had COVID-19 in the past or were infected by it.

The other type of diagnostic test, an antigen test, is known as a rapid diagnostic test. The test is given via a nasal or throat swab and the results are known in an hour or less. Positive results are usually highly accurate, but negative tests may need to be confirmed through a molecular test. It diagnoses an active coronavirus infection, but it cannot rule out such an infection. Antigen tests are more likely to miss an active coronavirus infection compared to a molecular test. Your health care provider may order a molecular test if your antigen test shows a negative result but you have symptoms of COVID-19.

An antigen test diagnoses an active coronavirus infection but cannot rule out such an infection. 

An antibody test looks for antibodies that are made by the immune system in response to a threat, such as a specific virus. Antibodies can help fight infections. This procedure is also known as a serology test, seriological test or blood test. It is performed via a finger stick or a blood draw. The result may be known the same day as the test, or it can take up to three days. Sometimes, the FDA says, a second test is needed to ensure an accurate result. This test shows whether you have been infected with coronavirus in the past.  It does not show that you don’t have COVID-19.

Information courtesy of the FDA. For more information on COVID-19, click here.