Serology tests. SARS-CoV-2 is the virus that causes COVID-19. The Serology test detects antibodies against SARS-CoV-2 in a blood sample taken from the test subject. The blood sample may be whole blood, serum or plasma. (In the case of coagulated whole blood, serum, or plasma the sample must be centrifuged.) Antibodies are produced by an adaptive immune response against the virus. Immune responses to viral infection may differ from patient to patient, take time to develop, and usually proceed in a phased manner.
Immune responses to SARS-CoV-2 may differ significantly from the usual immune response to viral pathogens. Initial immune responses to viral pathogens often produce a IgM antibodies soon after the infection, which lasts for a short period. Later in the course of a typical infection IgG antibodies are usually produced and these IgG antibodies may be detectable for months or years after infection. Detection of antibodies in a test subject’s blood are an indicator of past or current exposure to SARS-CoV-2, but do not necessarily indicate current infection. It is not currently known whether antibodies to SARS-CoV-2 provide full or partial immunity to the virus, and if so, for how long.
False negative results may occur when using the test. Reasons false negative results may be generated include, but are not limited to, a) a subject being tested is in the early stages of infection before the individual has mounted a detectable immune response, b) a subject is mounting an immune response to the virus but the immune response is not primarily directed against the viral antigens used in the design of the test, c) a subject was exposed to virus but never mounted a detectable antibody response, and/or d) a subject’s antibody levels have decreased below the limit of detection.
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