Any test on serum, but usually refers to the detection of antibodies as an aid to diagnosis, or for the detection of early infection or prior infection/immunity. (In practice, although not strictly accurate, the term is also used, faute-de-mieux, to describe antibody level tests done on other samples including, for example, the oral fluid samples used to retrospectively confirm or refute the diagnosis of measles, rubella, and mumps following notification.)
In the Virology/Microbiology laboratory, serology is most often used to detect pathogen-specific antibodies, e.g. anti-hepatitis C antibodies. The most common antibody classes detected are IgG and IgM. Serology can also be used to detect antigen e.g. hepatitis B surface antigen, Cryptococcus neoformans antigen (often abbreviated to CRAG).
There are several methods of detecting antibody levels:
- Enzyme-linked Immunosorbent Assay (ELISA)
- Latex agglutination
- Complement fixation test (CFT)
- Neutralisation assays
The results of an assay may be given as a number, but in some cases, the result will be in the form of a titre signifying the strength of the response.
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