Background: Although relationships between chronic Chlamydia pneumoniae (Cpn) infection and the risk of coronary events in stable coronary artery disease patients have been reported, a similar link in acute coronary syndrome (ACS) patients has not been consistently observed. Methods: In a nested case-control substudy of the Global Utilization of Strategies to Open Occluded Arteries IV Acute Coronary Syndromes trial, 295 cases (30-day death/myocardial infarction [MI]) were matched by age, sex, baseline creatine kinase-myocardial kinase, and smoking status with 295 control subjects. To test the hypothesis on 1-year mortality, another subset (n = 276) was drawn from the 590-patient cohort; 138 patients who died at 1 year plus the matching controls who survived at 1 year. We measured Cpn IgG and IgA antibody titers in baseline serum with microimmunofluorescence. Conditional logistic regression was used to quantify the prognostic relevance seropositivity (IgG ≥1:32; IgA ≥1:16) and elevated titer levels. Results: The prevalence of Cpn IgG and IgA was similar between cases and controls (30-day death/MI: IgG, 80% vs 85%, P = .126; IgA, 45% vs 37%, P = .079), and were not statistically significant predictors of 30-day death/MI after baseline adjustment. Likewise, the 1-year death cohort had comparable proportions of Cpn IgG and IgA among cases and controls (86% vs 91% [P = .265] and 49% vs 43% [P = .334], respectively), and did not add prognostic value. Conclusions: These findings are in concert with study results suggesting that chronic Cpn infection is not associated with 30-day death/MI or 1-year mortality in non-ST elevation ACS.

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Westerhout, C.M, Gnarpe, J, Chang, W.C, FitzPatrick, S, Barnathan, E.S, Boersma, H, … Armstrong, P.W. (2007). No prognostic significance of chronic infection with Chlamydia pneumoniae in acute coronary syndromes: Insights from the Global Utilization of Strategies to Open Occluded Arteries IV Acute Coronary Syndromes trial. American Heart Journal, 154(2), 306–312. doi:10.1016/j.ahj.2007.04.010