The
complement fixation test is an
immunological medical test that can be used to detect the presence of either specific
antibody or specific
antigen in a patient's
serum, based on whether
complement fixation occurs. It was widely used to diagnose infections, particularly with microbes that are not easily detected by culture methods, and in rheumatic diseases. However, in clinical diagnostics labs it has been largely superseded by other serological methods such as
ELISA and by DNA-based methods of pathogen detection, particularly
PCR.