Laboratory diagnosis of Mycoplasma pneumoniae infection. 3. Detection of IgM antibodies to M. pneumoniae by a modified indirect haemagglutination test.

The indirect haemagglutination (IHA) test was compared with the complement-fixation (CF) test for the measurement of antibodies to Mycoplasma pneumoniae. A modification of the IHA was used to measure M. pneumoniae IgM antibodies. Sera were obtained from various groups of patients who were either culture or antigen positive for M. pneumoniae in nasopharyngeal aspirates or who had fourfold or greater increase in CF antibody or a titre greater than or equal to 320. The results of these comparisons showed that the modified IHA test was specific and more sensitive (89% as opposed to 64%) than the CF test. The modified IHA test for the detection of IgM antibody was highly effective in the recognition of recent or current infection with the mycoplasma. It was also of equal sensitivity to an indirect enzyme immunoassay for the detection of IgM antibodies to M. pneumoniae.