Diagnosis of Mycoplasma pneumoniae infection by specific IgM antibodies using a new capture-enzyme-immunoassay.

A total of 1226 sera from 1055 patients with respiratory tract infections were tested. IgM antibodies were detected by an antibody-capture enzyme-immunoassay (Mp TEST, Diatech Diagnostica Ltd, Israel). Acute infection with IgM antibodies to Mycoplasma pneumoniae was detected in 211 patients. Presence of IgM was closely associated to some or all pneumonia-related symptoms. Eighty-one of IgM-positive patients treated with tetracycline or erythromycin responded positively. Of the 211 patients, 63 (30%) had low levels and 23 (11%) had moderate levels of IgM antibodies already in the first serum sample. In these 86 patients (41%) the complement fixation (CF) test was negative or very low positive. Thus in these cases, the CF test would have missed the early diagnosis in the first serum samples.