Association ofChlamydia pneumoniaeIgA antibodies with recently symptomatic asthma

Abstract

SummaryTo determine whether recently diagnosed adult–onset asthma is associated with serologic evidence of chronicChlamydia pneumoniaeinfection, we performed a case-control study in a primary care clinic of cases with asthma (25 adults reporting first symptoms of asthma within 2 years of enrollment) and 45 concurrently enrolled sex and age (±10 years) matched non-asthmatic controls with normal pulmonary function.C. pneumoniae-specific IgA, IgG and IgG4 antibodies, and circulating immune complexes (CIC) were measured by microimmunofluorescence testing. Results showed that frequencies of IgG litres>16 (92%), IgG4 litres>16 (20%) and CIC>4 (60%) in asthma patients were not significantly different from those of controls. However, asthmatics had a significantly higher prevalence ofC. pneumoniae-specific IgA litres>10 (72% of casesvs44% of controls,P< 0·05). After adjustment for the effects of age, sex and smoking, the odds ratio for an association of IgA and asthma was 3·7 (95% confidence interval 1·2–11·5). We conclude that recently symptomalic reversible airway obstruction in adults is associated with the presence ofC. pneumoniae-specific IgA antibodies, a proposed indicator of chronic respiratoryC. pneumoniaeinfection.