Mycoplasma pneumoniae infection: early diagnosis by detection of specific IgM by immunofluorescence.

An indirect immunofluorescent antibody test for early detection of IgM antibodies to Mycoplasma pneumoniae is described, using sera from which IgG antibodies have been removed. The results over a five-year period were studied and compared with complement fixation testing and isolation of the organism. During the epidemic season of November 1990 to April 1991, the immunofluorescent IgM test was used as a first-line test on specimens taken both early and late in the illness to provide a simple, inexpensive and clinically useful test, with 151 positive results being obtained from 886 sera tested.