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)
Key words
biological variation
cardiac troponin
diurnal rhythm
Abbreviations and Acronyms
AMI
acute myocardial infarction
BMI
body mass index
CI
confidence interval
CK
creatine kinase
cTn
cardiac troponin
cTnT
cardiac troponin T
CVi
within-person biological coefficient of variation
eGFR
estimated glomerular filtration rate
IQR
interquartile range
RCV
reference change value
Cited by (0)
This study was supported by a research grant from Stichting De Weijerhorst (Maastricht, the Netherlands) to Dr. van Dieijen-Visser. The authors have reported that they have no relationships relevant to the contents of this paper to disclose. The first 2 authors contributed equally to this work, and the Departments of Clinical Chemistry and Human Movement Sciences, Maastricht University Medical Center, contributed equally as well.
