Antigen diagnostic tests detect structural features of the outside of the virus called antigens, small proteins that make up the virus that may be present in a patient’s sample.
Over-the-counter antigen tests usually rely on the appearance of a colored line on the test cartridge to indicate a positive result. This means of providing a diagnostic result has been likened to the color changing lines on pregnancy tests, which can indicate the presence or absence of a pregnancy.
Antigen tests that rely on a change in fluorescence are performed in laboratories that have specialized readers to observe the fluorescence.
The immune system naturally produces proteins, called antibodies, in response to infection. Antibodies recognize and bind to foreign molecules, called antigens, on the surface of pathogens. When an antibody binds to an antigen, it seeks to disable the associated pathogen through direct or indirect mechanisms.
Blood samples are used as the specimen type for antibody testing.
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