Short- and Long-Term Risk Stratification Using a Next-Generation, High-Sensitivity Research Cardiac Troponin I (hs-cTnI) Assay in an Emergency Department Chest Pain Population

BACKGROUND: The next-generation, high-sensitivity cardiac troponin assays can measure quantifiable concentrations of cTn in a majority of individuals, but there are few studies assessing these assays for risk stratification. The present study was undertaken to determine if a research hs-cTnI assay can be useful for predicting death/myocardial infarction (MI), both short- and long-term, in an emergency department acute coronary syndrome (ACS) population. METHODS: In a cohort of 383 subjects, originally recruited in 1996, presenting to the emergency department with symptoms suggestive of ACS, the heparin plasma obtained at initial presentation was thawed and measured in 2007 with a research hs-cTnI assay. AccuTnI (Beckman Coulter) measurements were made on these same samples in 2003. The population was divided into 4 groups by hs-cTnI: <5.00, 5.00-9.99, 10.00-40.00, and >40.00 ng/L. Kaplan-Meier, Cox proportional hazards, ROC curves, and logistic regression analyses were used to identify which hs-cTnI concentrations were predictive of death/MI within 10 years after presentation. RESULTS: There were significant differences between the hs-cTnI groups for the probability of death/MI up to 10 years after presentation (P < 0.05). At 6 months, patients with hs-cTnI > or =10.00 ng/L were at higher risk for death/MI (hazard ratio >3.7; P < 0.05) compared with those having hs-cTnI <5.00 ng/L. ROC curve analysis for death/MI at 30 days with the hs-cTnI assay had an area under the curve of 0.74 (95% CI 0.65-0.82), with logistic models yielding an optimal assay threshold of 12.68 ng/L. CONCLUSIONS: This research hs-cTnI assay appears useful for risk stratification for death/MI in an ACS population.