Serological markers of Chlamydia pneumoniae infection in men and women and subsequent coronary events: The Scottish Heart Health Study cohort

Aims To investigate the relationship between serum markers of Chlamydia pneumoniae infection and subsequent coronary events. Methods and Results In a nested case-control study, based on the Scottish Heart Health Study cohort, we estimated IgG, IgA and IgM antibodies to C. pneumoniae, and circulating immune complexes containing C. pneumoniae antigen in baseline serum samples from 217 cases experiencing a subsequent coronary event during follow-up (mean 7·5 years) and from their matched controls. In men, the proportion of specimens positive for IgG, IgA and IgM antibodies showed no case-control differences (80% vs 80%, 57% vs 53% and 3% vs 3%, respectively). The odds ratio for a coronary event was 1·00 (95% confidence interval 0·59–1·69) for the presence of IgG antibodies to C. pneumoniae; 1·21 (0·76–1·92) for IgA and 0·75 (0·17–3·35) for IgM. Similar results were seen in women. The proportion of specimens with circulating immune complexes with C. pneumoniae antigen also showed no case-control differences (12% vs 12%, both sexes combined) with an odds ratio of 1·00 (0·57–1·76). Conclusion Prior infection with C. pneumoniae, as estimated by these markers, does not appear to be a risk factor for subsequent coronary heart disease