Comparison of serological tests for detection of immunoglobulin M antibodies to Chlamydophila pneumoniae

Background and objective: To evaluate an enzyme immunoassay (EIA) (AniLab C. pneumoniae) for detecting anti-Chlamydophila pneumoniae-specific IgM antibody, by comparing it with an ELISA, Hitazyme C. pneumoniae, and a micro-immunofluorescence (MIF) test. Methods: Antibodies in sera from three groups of patients were measured: eight serum samples collected serially from a patient with acute C. pneumoniae pneumonia, 34 serum samples with Hitazyme-ELISA false-positive results, and 137 serum samples from patients with community-acquired pneumonia. Results: The IgM antibody titre in the patient with acute C. pneumoniae pneumonia showed almost identical variation with the EIA, ELISA and MIF tests. Among the 34 samples found to be false-positive for IgM with ELISA, EIA revealed no positive cases. When a true positive case was defined as one for which a positive reaction was obtained with at least two tests, the sensitivities of the EIA, ELISA and MIF tests were 97.1%, 100% and 74.3%, with specificities of 100%, 37.3% and 100%, respectively. Conclusions: EIA was highly sensitive and specific as compared with the MIF test, and the ELISA test showed the lowest specificity. Consequently, the AniLab-EIA, rather than the Hitazyme-ELISA, is recommended as the routine method for accurately diagnosing acute C. pneumoniae infection.