Serum cystatin C was significantly higher in patients with poor collateralization than in those with good collateralization (1.08 ± 0.32 mg/L vs. 0.90 ± 0.34 mg/L, P < 0.001), and correlated inversely with Rentrop score before (Spearmen’s r = -0.263, P < 0.001) and after (Spearmen’s r = -0.145, P < 0.001) adjusting for gender, age, BMI, traditional risk factors for coronary artery disease (including smoking, hypertension, hyperlipidemia and diabetes), multi-vessel disease, GFR and serum level of hsCRP. The gene discussed is CST3; the disease is diabetes mellitus.