Background: No studies have measured plasma myeloperoxidase (MPO) across the entire spectrum of patients with coronary artery disease (CAD). The aim of the study was to compare MPO level across the entire spectrum of CAD, to assess the accuracy of MPO in predicting acute coronary syndromes and to define independent correlates of MPO level.
Design: This case-control study included 874 patients with angiographically proven CAD. Cases included 680 patients with CAD (382 patients with stable CAD, 107 patients with non-ST-segment elevation acute coronary syndromes and 191 patients with ST-segment elevation acute myocardial infarction). Controls included 194 subjects with normal coronary angiograms. MPO was measured using an enzyme immunoassay before angiography and heparin administration.
Results: MPO level [median (25th-75th percentiles)] was 74.5 (52.5-135.3) microg L(-1) in cases vs. 61.2 (44.6-80.9), microg L(-1) in controls (P < 0.001). MPO level was 61.2 (47.5-85.8), microg L(-1) in patients with stable CAD, 99.2 (62.2-154.9), microg L(-1) in patients with non-ST-segment elevation acute coronary syndromes and 129.5 (72.2-216.0) microg L(-1) in patients with acute myocardial infarction (P < 0.001). Elevated MPO level was associated with acute coronary syndromes with an area under receiver operating characteristic (ROC) curve of 0.731 (95% confidence interval 0.692-0.770; P < 0.001). Independent correlates of MPO level were acute coronary syndrome (P < 0.001), high-sensitivity C-reactive protein (P = 0.007), creatinine (P = 0.026), left ventricular ejection fraction (P = 0.027, negative association) and smoking (P = 0.028).
Conclusions: MPO level is elevated in patients with CAD and higher levels of MPO were found with progression of CAD from stable CAD to non-ST-segment elevation acute coronary syndromes and to acute myocardial infarction.