Myocardial Injury Thresholds for 4 High-Sensitivity Troponin Assays in U.S. Adults

Background: Myocardial injury is currently defined as a cardiac troponin above the sex-specific 99th percentile of a healthy reference population (upper reference limit [URL]). Objectives: The purpose of this study was to estimate high-sensitivity (hs) troponin URLs in a representative sample of the U.S. adult population; overall and by sex, race/ethnicity, and age group. Methods: Among adults participating in the 1999-2004 National Health and Nutrition Examination Survey (NHANES), we measured hs-troponin T using 1 assay (Roche) and hs-troponin I using 3 assays (Abbott, Siemens, and Ortho). In a strictly defined healthy reference subgroup, we estimated 99th percentile URLs for each assay using the recommended nonparametric method. Results: Of 12,545 participants, 2,746 met criteria for the healthy subgroup (mean age 37 years, 50% men). The NHANES 99th percentile URL for hs-troponin T (19 ng/L) matched the manufacturer-reported URL (19 ng/L). NHANES URLs were 13 ng/L (95% CI: 10-15 ng/L) for Abbott hs-troponin I (manufacturer: 28 ng/L), 5 ng/L (95% CI: 4-7 ng/L) for Ortho hs-troponin I (manufacturer: 11 ng/L), and 37 ng/L (95% CI: 27-66 ng/L) for Siemens hs-troponin I (manufacturer: 46.5 ng/L). There were significant differences in URLs by sex, but none by race/ethnicity. Furthermore, the 99th percentile URLs for all 4 hs-troponin assays were statistically significantly lower in healthy adults aged <40 years compared with healthy adults ≥60 years (all P < 0.001 by rank sum testing). Conclusions: We found URLs for hs-troponin I assays that were substantially lower than currently listed 99th percentile URLs. There were significant differences in hs-troponin T and I URLs by sex and by age group in healthy U.S. adults but none by race/ethnicity.