A SARS antibody test is a blood test that detects antibodies produced by the immune system after exposure to a SARS (Severe Acute Respiratory Syndrome) coronavirus. Antibodies are proteins made by the body to help recognize and fight infections.

The term “SARS antibody test” may refer to testing for antibodies against:

• SARS-CoV-1 (the virus that caused the original SARS outbreak in 2003), or more commonly in recent years,

• SARS-CoV-2 (the virus that causes COVID-19).

What the test detects

The test looks for antibodies such as:

• IgM antibodies: Usually appear earlier after infection and may indicate a more recent immune response.

• IgG antibodies: Typically appear later and may remain detectable longer, indicating past exposure or immune response.

(Some modern antibody tests measure total antibodies rather than separating IgM and IgG.)

What a positive result may mean

A positive SARS antibody test may indicate:

• Previous infection with the virus

• An immune response after vaccination (for SARS-CoV-2 tests)

• Exposure to viral proteins

What a negative result may mean

A negative result may indicate:

• No prior exposure

• Testing was done too soon before antibodies developed

• Antibody levels have decreased over time

• The test may not detect antibodies produced by a different strain or immune response

What the test does not tell you

• It does not reliably determine whether you are currently infected (a viral test such as PCR or antigen testing is typically used for active infection).

• It does not measure the exact level of immunity or guarantee protection from future infection.