Plasma concentrations of cystatin C in patients with coronary heart disease and risk for secondary cardiovascular events: more than simply a marker of glomerular filtration rate.

BACKGROUND Renal impairment (RI) is associated with worse prognosis. Recently, cystatin C has been shown to represent a potentially superior marker of the glomerular filtration rate compared with creatinine clearance (CrCl). We evaluated the impact of cystatin C and other markers of RI on prognosis in a large cohort of patients with coronary heart disease (CHD). METHODS Cystatin C, creatinine (Cr), and CrCl were determined at baseline in a cohort of 1033 patients (30-70 years) with CHD. Patients were followed for a mean of 33.5 months, and a combined endpoint [fatal and nonfatal cardiovascular disease (CVD) events] was used as the outcome variable. Cystatin C was measured by immunonephelometry, and CrCl was calculated. RESULTS During follow-up, 71 patients (6.9%) experienced a secondary CVD event. Neither Cr (P = 0.63) nor CrCl (P = 0.10) were associated with incidence of CVD events, whereas cystatin C was clearly associated with risk of secondary CVD events (P <0.0001). In multivariate analyses, patients in the top quintile of the cystatin C distribution at baseline had a statistically significantly increased risk of secondary CVD events even after adjustment for classic risk factors, severity of coronary disease, history of diabetes mellitus, treatment with angiotensin-converting enzyme inhibitors, and C-reactive protein (hazard ratio, 2.27; 95% confidence interval, 1.05-4.91) compared with patients in the bottom quintile. CONCLUSIONS These data support the possibly important prognostic value of cystatin C among patients with known CHD and suggest that it may be a useful clinical marker providing complementary information to established risk determinants.