Prognostic performance of a high-sensitivity assay for cardiac troponin I after non-ST elevation acute coronary syndrome: Analysis from MERLIN-TIMI 36

BACKGROUND: Newer troponin assays offer the ability to quantify circulating troponin levels at an order of magnitude lower than contemporary assays, fueling continued debate over the prognostic implications of very low-level increases in concentration. We evaluated the prognostic implications of low-level increases in cardiac troponin I (cTnI) using an investigational single-molecule high-sensitivity assay in patients with acute coronary syndrome (ACS). METHODS: We measured cTnI using both a high-sensitivity troponin I (hsTnI) assay (Erenna, Singulex, 99(th) percentile 9 pg/ml) and a current generation sensitive assay (TnI-Ultra, Siemens, 99(th) percentile 40 pg/ml) at baseline in 1807 patients with non-ST elevation ACS and compared their prognostic ability for adverse cardiovascular events at 30 days and one year. RESULTS: Among patients with TnI-Ultra<99(th) percentile, patients with elevated hsTnI (≥ 9 pg/ml) had a significantly higher risk than patients with hsTnI<9 pg/ml: cardiovascular death (CVD) or myocardial infarction (MI) at one year (7.0% vs 3.8%; p<0.001, hazard ratio (HR) 2.05, confidence interval (CI) 1.23-3.41); including a higher risk of CVD (3.5% vs 1.5%, p<0.001) and MI (5.0% vs 2.8%, p<0.001) individually. This higher risk of CVD/MI was independent of clinical risk stratification using the TIMI Risk Score (adj. HR 1.76, CI 1.05-2.90). Moreover, hsTnI showed a trend toward a gradient of risk even below the hsTnI 99 percentile. CONCLUSIONS: Low-level cardiac troponin detected using a single-molecule technique, below the cutpoint of a contemporary sensitive assay, identified a significant gradient of risk. These findings support the prognostic relevance of low-level cardiac troponin elevation with increasingly sensitive assays in patients with ACS.