PCR (Polymerase Chain Reaction): This tests for the presence of the actual virus’s genetic material (RNA) or its fragments as it breaks down. It is heated and cooled using special reagents to convert the virus's RNA into DNA, and then make millions of copies of the DNA, which allows for the identification of the organism. This is the most reliable and accurate test for detecting active infection.

• It can help identify people who are contagious to others (including asymptomatic)
• It can be used to determine who has an active infection.

Antigen: This test detects bits of proteins on the surface of the virus called antigens. Antigen tests are typically considered rapid, taking only 15 to 30 minutes but are less accurate than a PCR test. Rapid antigen tests are most accurate when used within a few days of the start of your symptoms, which is when the largest amount of virus is present in your body. Because this test is not as accurate as a PCR test, if an antigen test is negative, your healthcare provider may order a PCR test

• It can be used to quickly determine who has an active infection.
• It can help identify people who are contagious to others.
• It is a less expensive test than a molecular test.

This tests detects if you’ve had an immune response (antibodies) to the virus. This means that you’ve had the virus and your body (immune system, specifically antibodies) has mounted an attack to fight it. The test is detecting those antibodies. It typically takes about a week after being infected for enough antibodies to develop to be detected in your blood. For this reason, this test shouldn’t be used to diagnose an active infection.

Immunoglobulin M (IgM) is the first antibody that is formed against a germ, so it appears on tests first, usually within 1-2 weeks.

Immunoglobulin G (IgG), which appears on tests about 2 weeks after the illness starts. IgM usually disappears from the blood within a few months, but IgG can last for years. Some antibody tests test for IgM and IgG, and some only test for IgG.