[The complement fixation reaction: a traditional, updated method for the detection of antibodies in the diagnosis of infections].

Complement-fixation (CF) is still an important basic serologic test for the diagnosis of infectious diseases. In several areas of microbiology (viral, bacterial, parasitic and fungal) it has served as a reference standard against which other methods have been compared. Its partial displacement by other techniques, as advocated in some recent literature, is often unfounded and uncritical; displacement is mostly due not to problems inherent in the method, but rather to the lack of reagents of satisfactory quality. The CF technique has been greatly improved in recent years. Improvements include the replacement of reaction tubes with microtiter 96-well plate systems, the availability of semi-automated and automated pipetting devices, the wide range of commercially offered antigens (over 60, by far larger than the range of antigens available for other test systems), an extreme stability of freeze-dried reagents with shelf-lives over decades and, last but not least, low reagent costs (particularly if compared with some other methods). For some diseases CF is still the method of choice (Campylobacter jejuni, Neisseria gonorrhoeae, Mycoplasma pneumoniae, Influenza A and B and some other respiratory viruses). CF has been recognized as a confirmatory test for Lyme disease (B. burgdorferi) and, probably, for Legionellosis. It has been used routinely for the follow-up of antibiotic treatment in syphilis and, recently, in Helicobacter pylori infections. A positive CF result is also indicative for the treatment of complications in Entamoeba histolytica carriers.(ABSTRACT TRUNCATED AT 250 WORDS)