Direct Comparison of the Circadian Rhythm of Cardiac Myosin-Binding Protein C (cMyC) and Cardiac Troponin.

Abstract

We have previously shown that significant circadian oscillations exist for cardiac troponin T (cTnT) but not for cardiac troponin I (cTnI) (1). Cardiac myosin-binding protein C (cMyC) is a novel protein biomarker of myocardial injury with a promising role in the diagnosis and risk stratification of acute myocardial injury. In this study, we examine and compare the diurnal variation of cMyC with cTnT/I. Study design, population and methods are described by Klinkenberg et al. (1). Briefly, 26 consecutive hourly blood samples were drawn between 8.30 Am and 09.30 Am (+ 1 day) from 24 individuals without active cardiac disease, uncontrolled hypertension, anemia, renal dysfunction, or a history of acute myocardial infarction or stroke within 12 months. Seven percent had type 2 diabetes (all on oral blood glucose lowering medications) and 42% were on antihypertensive medication. cMyC was measured by Millipore Sigma (2). Limit of detection 0.4 ng/L, limit of quantitation (20% analytical coefficient of variation) of 1.2 ng/L; intra-series precision (CV, 11 +/− 3%), and inter-series precision (CV, 13 +/− 3%), 99th percentile is 87 ng/L. cTnT (Roche hs-cTnT) and cTnI (Abbott hs-cTnI) were measured previously by Klinkenberg et al. (1), but data were reanalyzed and are represented here to enable direct comparisons with cMyC.