Effect of obesity on the relationship between plasma C-reactive protein and coronary artery stenosis in patients with stable angina

Introduction: The association between plasma C-reactive protein (CRP) and the extent of coronary artery disease (CAD) in patients with stable angina remains controversial. Obesity is strongly associated with elevated CRP levels, potentially confounding the relationship between CRP and CAD severity. Methods and results: We studied 830 subjects without CAD and 218 patients with CAD undergoing elective coronary angiography. Geometric means of CRP were computed in a two-way analysis of covariance model in which study participants were stratified into nine groups according to CAD status (no CAD, single-vessel disease or multivessel disease) and tertiles of BMI. There was a significant interaction between CAD and categories of BMI with regard to CRP level (P = 0.002). In the lower tertile of BMI, patients with CAD had markedly higher CRP concentration compared to control subjects (1.16, 1.80 and 2.82 mg/L in subjects without CAD, patients with single-vessel disease and patients with multivessel disease, respectively; P = 0.003). However, the relationship between CRP and CAD became weaker for patients in the second BMI tertile (P = 0.15), whereas no significant relationship was observed for patients in the third BMI tertile (P = 0.75). In patients undergoing coronary angioplasty (n = 195), BMI was independently related to the magnitude of the angioplasty-induced CRP elevations (P = 0.002). Conclusion: The level of obesity is essential to the interpretation of the relationship between CRP and severity of CAD. The production of inflammatory mediators with increasing levels of obesity becomes the dominant determinant of plasma CRP levels and masks the vascular contribution due to CAD.