There are three different types of tests – molecular, antigen and antibody tests. The most common molecular test is the polymerase chain reaction (PCR) test. Molecular and antigen tests are both considered to be diagnostic tests.

A PCR or antigen test is used to identify an active coronavirus infection. PCR tests detect the COVID-19 virus’ genetic material. The antigen test detects proteins on the surface of the virus.

The antibody tests looks for antibodies that are made by a person’s immune system in response to a COVID-19 infection. According to the FDA, antibodies most commonly become detectable 1–3 weeks after symptom onset, at which time evidence suggests that infectiousness likely is greatly decreased and that some degree of immunity from future infection has developed. Antibody tests are commonly used to determine if the test subject has previously had a COVID-19 infection.

The table below summarizes the primary types of COVID-19 tests.

Coronavirus Tests

Molecular Test Antigen Test Antibody Test
Also known as: Diagnostic test, viral test, molecular test, nucleic acid amplification test (NAAT), RT-PCR test, LAMP test Rapid diagnostic test (some molecular tests are also rapid tests) Serological test, serology, blood test, serology test
How the sample is taken: Nasal or throat swab (most tests)

Saliva (a few tests)

Nasal or throat swab

Saliva (from Inspire Health

Finger stick or blood draw
How long it takes to get results: Same day (some locations) or up to a week One hour or less

Approximately 15 minutes

Sam day (many locations) or 1-3 days

Approximately 15 minutes

Is another test needed: This test is typically highly accurate and usually does not need to be repeated. Positive results are usually highly accurate, but negative results may need to be confirmed with a molecular test. Sometimes a second antibody test is needed for accurate results.
What it shows: Diagnoses active coronavirus infection Diagnoses active coronavirus infection Shows if you’ve been infected by coronavirus in the past
What it can do: Show if you ever had COVID-19 or were infection with the coronavirus in the past. Definitely rule out active coronavirus infection.  Antigen tests are more likely to miss an active coronavirus infection compared to a molecular tests.  Your health care provider may order a molecular test if your antigen test shows a negative result but you have symptoms of COVID-19 Diagnose active coronavirus invection at the time of the test or show that you do not have COVID-19

Source:  Coronavirus Testing Basics, CDC, July 2020