Prognostic Implications of Low Level Cardiac Troponin Elevation Using High‐Sensitivity Cardiac Troponin T

BACKGROUND: High-sensitivity cardiac troponin T (hsTnT) is used in many countries, but is not available in the United States. Prior evidence has been viewed as inconclusive as to whether low cardiac troponin T (cTnT) concentrations detected with hsTnT are prognostically meaningful compared with fourth-generation cTnT. HYPOTHESIS: The aim of this study was to assess the prognostic performance of low-level cTnT elevations using the hsTnT assay compared with the assay (fourth-generation) currently available in the United States. METHODS: We measured serum cTnT in 4160 patients with non-ST-elevation acute coronary syndrome using both the hsTnT and fourth-generation assays. Patients were stratified at the 99th percentile cut point for each assay. RESULTS: Patients with baseline hsTnT ≥14 ng/L (n = 3697) vs <14 ng/L were at higher 30-day risk of cardiovascular death (CVD) or myocardial infarction (MI) (9.1% vs 1.9%, P < 0.0001). After adjusting for all other elements of the Thrombolysis In Myocardial Infarction risk score, hsTnT ≥14 carried a 5.2-fold higher risk of CVD/MI (95% confidence interval [CI]: 2.6-10.1, P < 0.0001). Low levels of hsTnT (14-50 ng/L) also revealed increased risk (CVD/MI: 6.4%, P = 0.002). Importantly, patients with negative fourth-generation cTnT but positive hsTnT were at 4.5-times higher risk of CVD/MI (95% CI: 1.9-11.0, P = 0.0008) than patients with negative hsTnT. In contrast, patients with a negative hsTnT but positive fourth-generation cTnT result had a lower rate of CVD/MI than with a positive hsTnT (1.3% vs 8.2%, P = 0.0005). CONCLUSIONS: Low-level increases in cTnT detected using the hsTnT assay identified patients at a meaningfully higher risk and who might otherwise be missed, and improves upon risk stratification using the cTnT assay currently available in the United States.