Prognostic Value of the Ortho Vitros Cardiac Troponin I Assay in Patients With Symptoms of Myocardial Ischemia

Abstract

We evaluated the risk assessment value of a commercial cardiac troponin (cTn; Ortho Vitros ECi, Ortho-Clinical Diagnostics, Raritan, NJ) I assay in patients with symptoms of myocardial ischemia suggestive of acute coronary syndrome and compared findings with those for a commercial cTnT assay in the same population. The cTn levels were measured by both assays in plasma samples from 273 patients during 24 hours after admission. Baseline and maximum concentrations were used for risk stratification; cutoffs were the 99th percentile and 10% coefficient of variation. End points were all-cause death and cardiac events within 60 days. Relative risks (RRs) were estimated using Cox proportional hazards regression models and Kaplan-Meier curves. RRs of cardiac events and death were significantly higher with increased baseline and maximum concentrations using either cTnI cutoff. The respective mortality rates for baseline cTnI of more than 0.08 μg/L vs 0.08 μg/L or less were 17.4% vs 2.9% ( P = .001); cardiac event rates were 11.5% vs 3.6% ( P = .03). Exclusion of patients with ST-segment elevation had no significant effect on rates for either assay. Mortality was higher in the intermediate (0.09–0.2 μg/L) than in the low (≤0.08 μg/L) group for cTnI, with directionally similar results for cTnT. Our findings validate the Ortho cTnI assay as a risk stratification biomarker in patients with symptoms of myocardial ischemia.