Chlamydia pneumoniae serology: Importance of methodology in patients with coronary heart disease and healthy individuals

Most publications on the relationship between infection with Chlamydia pneu moniae and coronary heart disease (CHD) propose an association, but negativ e studies are also reported. Seroepidemiological studies vary in the use of different serological methods, different cutoff limits, different sampling times in relation to acute cardiac events, and different clinical stages o f CHD. We wanted to compare three different commercially available methods for measuring Chlamydia antibodies to see how the choice of method influenc ed the prevalence of seropositive individuals in CHD patients and in health y individuals and to see if sampling time in relation to an acute cardiac e vent or the stage of atherothrombotic disease influenced the results. Blood samples from 197 CHD patients and 197 individually matched healthy control individuals were tested at baseline and after 6 months; the mean age was 5 5 years in both groups, and 18% were women. Among the CHD patients, 166 wer e included at a median of 16 days after an acute cardiac event and 31 had c hronic disease with the latest acute event being >3 months earlier. The dif ference in prevalence of antibodies between the CHD patients and the health y controls was significant when Chlamydia lipopolysaccharide antibodies wer e measured, while no significant differences between the study groups were observed by the two methods detecting Chlamydia pneumoniae major outer memb rane protein antibodies. The number of seropositive individuals was quite s imilar at inclusion and 6 months later, and no significant differences were observed between patients with a recent cardiac event and those with a mor e remote cardiac event. We conclude that the choice of serological method i s of major importance when evaluating a possible relationship between C. pn eumoniae and CHD.