Cardiac Troponin Risk Stratification Based on 99th Percentile Reference Cutoffs in Patients With Ischemic Symptoms Suggestive of Acute Coronary Syndrome: Influence of Estimated Glomerular Filtration Rates

Abstract

Cardiac troponin (cTn) assays were compared in 490 unselected patients with symptoms suggestive of acute coronary syndrome with varying renal functions for risk stratification. cTnI (Dade, Newark, NJ; Beckman, Chaska, MN; and Tosoh, South San Francisco, CA) and cTnT (Roche, Indianapolis, IN) measurements and estimated glomerular filtration rates (eGFRs) were obtained and classified along sex-derived cutoffs. The cTn levels were increased in 14% to 25% of patients. In 68%, the eGFR was 60 mL/min/1.73 m2 or more; in 17%, it was between 41 and 59; and in 15%, it was 40 or less. There were 36 deaths and 9 cardiac events. Risk stratification was significant at 30 days and 6 months (P = .05). Relative risks ranged from 3.1 to 3.7, and cumulative event rates ranged from 22.4% to 24.2% for an increased troponin level compared with 6.7% to 8.9% for a normal level. The 6-month event rate with an eGFR less than 60 mL/min/1.73 m2 and an increased troponin level ranged from 29.9% to 50.8% compared with 4.9% to 6.6% for a normal troponin level and an eGFR greater than 60 mL/min/1.73 m2 (P < .05). The eGFR in combination with an increased cTn level demonstrated the most powerful stratification.