Chlamydia pneumoniae and newly diagnosed asthma: a case-control study in 1 to 6-year-old children.

The aim of the study was to evaluate the association between antibodies to Chlamydia pneumoniae and the onset of asthma in children. In 1996-2000, 122 children aged 1-6 years, who were treated for new asthma as inpatients or outpatients in our hospital, were recruited. For each patient, two controls, matched by age, sex and municipality, were randomly selected from the same population. In 2000, 104 serum samples were available from patients (85%) and 120 from controls (49%) for microimmunofluorescence (MIF) assay for C. pneumoniae and C. trachomatis antibodies, and for enzyme immunoassay (EIA) for C. pneumoniae antibodies. In EIA, the median IgG concentrations were 20 EIU (EIA units) in the patients, and 16 EIU in the controls. IgG was positive (> 30 EIU) in 37 (36%) patients and in 36 (31%) controls. IgA was positive (> 12 EIU) in four (4%) patients and in eight (7%) controls. In MIF, four (4%) patients and seven (6%) controls were IgG positive, and seven were also IgA positive. IgM antibodies were detected in four children by EIA, and in none by MIF. IgG antibodies to C. pneumoniae, though common in 1 to 6-year-old children as detected by EIA, did not differ between newly diagnosed asthma patients and controls in this case-control study.