Preoperative cardiac troponin below the 99th-percentile upper reference limit and 30-day mortality after noncardiac surgery.

Preoperative high-sensitivity cardiac troponin (hs-cTn) above the 99th-percentile upper reference limit (URL) is associated with mortality after noncardiac surgery. This study aimed to evaluate whether preoperative hs-cTn concentrations above the lowest limit of detection (LOD) but below the 99th-percentile URL can predict mortality after noncardiac surgery.From January 2010 to April 2019, a total of 12,415 noncardiac surgical patients with preoperative hs-cTn I below the 99th-percentile URL were enrolled. The patients were divided into two groups according to preoperative hs-cTn I concentration: (1) [hs-cTn] below the LOD (6 ng/L), and (2) mildly elevated [hs-cTn] but below the 99th-percentile URL (40 ng/L). The primary outcome was 30-day mortality. Of the 12,415 patients enrolled, 7958 (64.1%) were in the LOD group whereas 4457 (35.9%) were in the mild elevation group. The incidence of 30-day mortality was significantly greater in the mild elevation group (2.1% vs. 4.0% hazard ratio [HR] 1.73; 95% confidence interval [CI] 1.39-2.16; p < 0.001) in the multivariate analyses. The propensity score matched analyses also produced a similar result (2.6% vs. 4.2% HR 1.61; 95% CI 1.26-2.07; p < 0.001). The threshold at which the risk of mortality increased corresponded to a preoperative hs-cTn I ≥ 12 ng/L. Patients with preoperative hs-cTn I above the LOD and below the 99th-percentile URL had greater 30-day mortality after noncardiac surgery.