Key result
cTnT concentrations exhibit a diurnal rhythm dropping ~30% from morning peaks during the daytime.
Why the study?
Diagnosing AMI relies on serial cTn testing and kinetic interpretation, but whether chronically elevated cTnT levels fluctuate randomly around a homeostatic set point was an unverified assumption.
Observational (n=23)
Cardiac troponin T levels exhibit a significant diurnal rhythm with morning peaks, highlighting the need to interpret dynamic cTnT changes in relation to sampling time and clinical presentation.
Diurnal cTnT variation may confound serial testing interpretation in chronic elevation; leaves open need for time-adjusted AMI thresholds.
Objectives The goal of this study was to test the unverified assumption that chronically elevated cardiac troponin T (cTnT) levels fluctuate randomly around a homeostatic set point. Background The introduction of high-sensitivity cardiac troponin (cTn) assays has improved sensitivity for acute myocardial infarction (AMI). However, many patients with a single positive cTn test result do not have AMI. Therefore, the diagnosis of AMI relies strongly on serial testing and interpretation of cTn kinetics. Essential in this regard is a profound understanding of the biological variation of cTn. Methods Two studies were conducted to assess biological cTnT variation and to investigate the presence of a diurnal rhythm of cTnT. Study 1 comprised 23 male subjects with type 2 diabetes, with no acute cardiovascular disease. Serial venous blood samples were drawn over an 11-h period (8:30 AM to 7:30 PM). In study 2, the presence of a diurnal cTnT rhythm was investigated by hourly sampling of 7 subjects from study 1 over 25 h. Results In study 1, we observed a gradual decrease in cTnT concentrations during the day (24 +/- 2%). This decrease was present in all participants and was most prominent in subjects with the highest baseline cTnT values (Pearson's R 0.93). Diurnal variation of cTnT, as assessed in study 2, was characterized by peak concentrations during morning hours (8:30 AM, 17.1 +/- 2.9 ng/l), gradually decreasing values during daytime (8:30 PM, 11.9 +/- 1.6 ng/l), and rising concentrations during nighttime (8:30 AM the next day, 16.9 +/- 2.8 ng/l). Conclusions A diurnal cTnT rhythm substantiates the recommendation that all dynamic changes in cTnT should be interpreted in relation to the clinical presentation. Epidemiological studies and risk-stratification protocols with the use of cTnT may benefit from standardized sampling times. (Exercise and Glycemic Control in Type 2 Diabetes; NCT00945165) Original language English Pages (from-to) 1788-1795 Number of pages 8 Journal Journal of the American College of Cardiology Volume 63 Issue number 17 DOIs https://doi.org/10.1016/j.jacc.2014.01.040 Publication status Published - 1 Jan 2014
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Klinkenberg et al. (2014) conducted an observational in Type 2 diabetes (n=23). Time of day was evaluated on Biological cTnT variation and diurnal rhythm. Cardiac troponin T concentrations exhibited a diurnal rhythm, peaking in the morning (17.1 +/- 2.9 ng/l) and gradually decreasing during the daytime (11.9 +/- 1.6 ng/l).
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