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Marc P Bonaca, Ryan G O’Malley, Sabina A Murphy, Petr Jarolim, Michael J Conrad, Eugene Braunwald, Marc S Sabatine, David A Morrow, Prognostic performance of a high-sensitivity assay for cardiac troponin I after non-ST elevation acute coronary syndrome: Analysis from MERLIN-TIMI 36, European Heart Journal. Acute Cardiovascular Care, Volume 4, Issue 5, 1 October 2015, Pages 431–440, https://doi.org/10.1177/2048872614564081
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Abstract
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).
We measured cTnI using both a high-sensitivity troponin I (hsTnI) assay (Erenna, Singulex, 99th percentile 9 pg/ml) and a current generation sensitive assay (TnI-Ultra, Siemens, 99th 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.
Among patients with TnI-Ultra<99th 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.
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.
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