Serological diagnosis of Mycoplasma pneumoniae infections: a critical review of current procedures.

Respiratory diseases due to Mycoplasma pneumoniae are still confirmed with serological methods, although during the acute phase of M. pneumoniae disease indicative parameters are frequently negative. This result is true not only for serodiagnosis based on tests for the presence of cold hemagglutinin (the first but unspecific acute-phase parameter; these are positive in only about 50% of cases) but also for serodiagnosis based on CF tests, particle agglutination tests, or even enzyme-linked immunoassays that test for "early" IgM antibodies. Whereas the sensitivity of the different tests is difficult to improve, advances in specificity were obtained with use of more defined protein antigen preparations of M. pneumoniae cells. Even more problematic than negative titers in the first serum samples and delayed positive titers in the convalescent-phase sera are false-negative results with sera from immunocompromised patients, which limit the value of serological approaches for diagnosis of M. pneumoniae infections in particular risk groups. This review summarizes the use and the limitations of various serological approaches but also refers to alternative methods that are suitable for diagnosis of acute-phase M. pneumoniae disease or cases in which seroconversion has not occurred.