Active and total myeloperoxidase in coronary artery disease and relation to clinical instability

The aim of this study was to evaluate the correlation between serum total and active myeloperoxidase (MPO) levels and the presence of coronary artery disease in consecutive patients evaluated by coronary angiography and to correlate the levels of the enzyme with instability.

Prospective analysis of serum samples of patients before coronary angiography. Total and active MPO concentrations were assessed by the sandwich Elisa and SIEFED® methods. Stable and unstable patients were separated into two groups. Differences between groups were analysed using the Student t test, chi square test or Fisher exact test, as appropriate. The relationship between total and active MPO was assessed using linear and curvilinear regression. Two hundred and twenty patients were included (age 66±11 years, 67% male) in the study. Among these, 62% presented significant coronary artery disease. Twenty-four patients (11%) presented unstable coronary syndrome. Mean active and total MPO levels in the population were 50.1±63.5 and 147.6±223.3 ng.mL(-1), respectively. In stable patients, mean active MPO was 47.1±47.9 ng.mL(-1) and in unstable patients 75.1±135.2 ng.mL(–1) (P=0.04). Mean total MPO was 146.3±224.7 ng.mL(-1) in the stable patients and 158.2±215.8 ng.mL(-1) in the unstable patients (P=0.8). Unstable patients had a significantly higher level of active MPO than stable patients but there was no significant difference between unstable and stable patients regarding total MPO.

A correlation was observed between active MPO and clinical instability but not with total MPO. These results suggest that this marker could be a powerful indicator of instability and could have a prognostic impact.