High-Sensitivity Cardiac Troponin T: Association of Creatine Kinase Catalytic Activity With the 99th Percentile

To the Editor:Fast diagnosis is the ultimate ambition for precise treatment of patients with acute myocardial infarction. Cardiac troponin (cTn)1 is considered the biomarker most specific for ischemia-related myocardial necrosis. With implementation of high-sensitivity (hs)-cTn assays, which detect cTn in ≥50% of a healthy population and exhibit ≤10% imprecision at the diagnostic cutoff, sex-specific differences have been reported (1). Recently, 3 contemporary sensitive central laboratory cTnI assays were compared in the same large reference population. For one of the assays, sex-dependent differences in the 99th percentile were detected (2). Physical activity and its surrogate marker creatine kinase (CK) activity were identified to have a positive association with cTnI. Importantly, adjustment for physical activity or CK activity abrogated the impact of sex (2).Here, the performance of an hs-cTnT assay was evaluated in the same reference population, with consideration of the influences of age, sex, and CK activity on the 99th percentile. Specimens originated from the well-characterized DONOR SHIP cohort collected in 2005 (2). Aliquots were thawed and hs-cTnT was measured by means of the Cobas e411 (Roche Diagnostics) in 2015. CK activity and other parameters were determined immediately after sampling. Aliquots of plasma samples have been stored for 10 …