Cystatin C for Enhancement of Risk Stratification in Non-ST Elevation Acute Coronary Syndrome Patients with an Increased Troponin T

BACKGROUND: We assessed the value of cystatin C for improvement of risk stratification in patients with non-ST elevation acute coronary syndrome (nSTE-ACS) and increased cardiac troponin T (cTnT), and we compared the long-term effects of an early invasive treatment strategy (EIS) with a selective invasive treatment strategy (SIS) with regard to renal function. METHODS: Patients (n = 1128) randomized to an EIS or an SIS in the ICTUS trial were stratified according to the tertiles of the cystatin C concentration at baseline. The end points were death within 4 years and spontaneous myocardial infarction (MI) within 3 years. RESULTS: Mortality was 3.4%, 6.2%, and 13.5% in the first, second, and third tertiles, respectively, of cystatin C concentration (log-rank P <0.001), and the respective rates of spontaneous MI were 5.5%, 7.5%, and 9.8% (log-rank P = 0.03). In a multivariate Cox regression analysis, the cystatin C concentration in the third quartile remained independently predictive of mortality [hazard ratio (HR), 2.04; 95% CI, 1.02-4.10; P = 0.04] and spontaneous MI (HR, 1.95; 95% CI, 1.053.63; P = 0.04). The mortality rate in the second tertile was lower with the EIS than with the SIS (3.8% vs 8.7%). In the third tertile, the mortality rates with the EIS and the SIS were, respectively, 15.0% and 12.2% (P for interaction = 0.04). Rates of spontaneous MI were similar for the EIS and the SIS within cystatin C tertiles (P for interaction = 0.22). CONCLUSIONS: In patients with nSTE-ACS and an increased cTnT concentration, mild to moderate renal dysfunction is associated with a higher risk of death and spontaneous MI. Use of cystatin C as a serum marker of renal function may improve risk stratification. (C) 2009 American Association for Clinical Chemistry