An assessment of a new diagnostic indirect enzyme immunoassay for the detection of anti-Mycoplasma pneumoniae IgM.

A new and rapid IgM enzyme immunoassay (EIA)(Immuno Well, Gen-Bio, San Diego, CA) was evaluated for its ability to accurately establish a serodiagnosis for acute Mycoplasma pneumoniae infection. Case definitions were established with the combination of complement fixation (CF) serology, IgM anti-P1 immunoblotting, and clinical and other laboratory data. In an asymptomatic population of 52 children and adults, the EIA was positive for 3.9%. For 17 serum pairs for which there was evidence of a greater than or equal to 4-fold rise in CF titer, 5 acute sera (29.4%) and 14 convalescent sera (82.3%) were positive. In applying the assay to sera that were acquired from a prospective study of childhood infection where the positive case definition was maintained for 22.3% of patients, the sensitivity, specificity, positive predictive value, and negative predictive value for the EIA was 90.5%, 93.2%, 79.2%, and 97.1%, respectively. When the EIA results of a "low-positive," as defined by the manufacturer, were excluded from the positive group, the respective values were 81.0%, 97.3%, 89.5%, and 94.7%. The accuracy of this new assay will be influenced by the prevalence of true illness in the populations to which it may be applied.