Chest, Vol 102, 477-481, Copyright © 1992 by American College of Chest Physicians

ARTICLES

IgM anti-P1 immunoblotting. A standard for the rapid serologic diagnosis of Mycoplasma pneumoniae infection in pediatric care

N Cimolai and AC Cheong
Department of Pathology, University of British Columbia, Vancouver, Canada.

STUDY OBJECTIVE: To prospectively evaluate the use of an IgM anti-P1 immunoblotting assay for the rapid diagnosis of Mycoplasma pneumoniae infection in a pediatric setting. PATIENTS AND METHODS: Blood specimens from 107 children representing 108 predominantly respiratory illnesses were obtained for a prospective evaluation of the IgM anti-P1 assay. Primary patient diagnoses were determined by a combination of the complement fixation test and supplementary microbiologic and nonmicrobiologic diagnostic tests. The potential effect of the assay results on antibiotic therapy was assessed by observing concurrent therapy. RESULTS: M pneumoniae was the primary etiologic agent of disease in 19 patients. The sensitivity, specificity, positive predictive value, and negative predictive value of the IgM test to determine a case of primary M pneumoniae disease was 84.2 percent, 95.5 percent, 80.0 percent, and 96.6 percent, respectively. Twenty-seven children may have had antimicrobial therapy appropriately modified if results of the assay were directly utilized. Three of four patients with positive assays, which would have been falsely indicative of primary disease, had evidence of a recent probable M pneumoniae infection shortly preceding the acute illness. CONCLUSION: The rapid IgM anti-P1 assay is reasonably specific for the diagnosis of M pneumoniae infection. Apart from establishing prompt and accurate diagnosis, the results have the potential to change treatment measures in a significant proportion of patients.