Clinical Efficacy of Three Assays for Cardiac Troponin I for Risk Stratification in Acute Coronary Syndromes: A Thrombolysis In Myocardial Infarction (TIMI) 11B Substudy

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Abstract
Background: Significant analytic variability exists between the multiple assays for cardiac troponin I (cTnI) approved for clinical use. Until adequate cTnI standardization is possible, an evidence-based approach evaluating each assay at specific thresholds appears warranted. Methods: We examined the efficacy of three cTnI assays for predicting death, myocardial infarction (MI), or the composite of death, MI, or urgent revascularization at 43 days among patients with non-ST-elevation acute coronary syndromes enrolled in the Thrombolysis In Myocardial Infarction (TIMI) 11B study. Results: Six hundred eighty-one patients with serum samples obtained at baseline and/or 12–24 h had cTnI determined using all three assays. Baseline cTnI was ≥0.1 μg/L for 368, 395, and 418 patients with the Bayer Immuno 1TM, ACS:180®, and Dimension® RxL assays, respectively. Correlation coefficients for the RxL with the ACS:180 and Bayer Immuno 1 results were 0.89 (P = 0.0001) and 0.87 (P = 0.0001), with a coefficient of 0.92 (P = 0.0001) for the ACS:180 and Bayer Immuno 1 assays. Patients with cTnI ≥0.1 μg/L were at increased risk for death or MI by 43 days (relative risk, 2.2–3.0; P P Conclusion: This study demonstrates the prognostic efficacy of three independently developed cTnI assays at a threshold of 0.1 μg/L for the prediction of adverse clinical outcomes among patients with non-ST-elevation acute coronary syndromes.