Supplementary Material for: Elevated cystatin-C levels are associated with increased mortality in acute coronary syndrome patients: An HIJ-PROPER Sub-Analysis

Background and aims: We investigated the association between serum cystatin-C levels and cardiovascular events in patients with acute coronary syndrome. Methods: Data of 1,100 patients from the prospective parent study were included. Patients hospitalized for acute coronary syndrome were divided into four groups based on quartiles (Q) of cystatin-C levels (mg/L) within 24-hours of admission: Q1, ≤0.82; Q2, 0.821.12. The primary endpoint of this study was all-cause mortality and secondary endpoint was composite of all-cause mortality, non-fatal myocardial infarction, non-fatal stroke, unstable angina pectoris, or ischemia-driven revascularization. Results: During a median observation period of 4.0 years, the primary endpoint was noted in 5, 12, 18, and 36 patients in Q1, Q2, Q3, and Q4, respectively, with corresponding incidence rates of 1.8%, 4.4%, 6.5%, and 13.5%, respectively (p<0.0001 for difference among four groups). This association persisted even after adjusting for patient characteristics and other laboratory results at baseline (p=0.04). A stepwise increase in the incidence rate of the secondary endpoint with an incline in cystatin-C levels was observed in the non-adjusted model (26.6%, 33.3%, 32.3%, and 39.1% in Q1, Q2, Q3, and Q4, respectively; p=0.01), but not in the adjusted model (p=0.3). No difference was observed in the incidence rate of non-fatal myocardial infarction (p=0.89), non-fatal stroke (p=0.3), unstable angina pectoris (p=0.49), and ischemia-driven revascularization (p=0.47) with an incline in cystatin-C levels. Conclusion: Elevated cystatin-C levels were associated with increased all-cause mortality but not cardiovascular events other than mortality in acute coronary syndrome patients.