Diurnal variation in admission troponin concentrations in patients with chest pain in the emergency department

Background: Recent studies have suggested that there may be large diurnal variation in cardiac troponin T (cTnT) concentrations measured with a high sensitive assay. Objective: To investigate if clinically relevant diurnal variation in cTnT concentrations is present in patients with chest pain in the emergency department (ED). Methods: We included all patients with chest pain, but no myocardial infarction (MI), and no other acute condition that may affect troponin concentrations in the ED at Karolinska University Hospital, Stockholm, Sweden, 2011-2014. Time periods for blood sampling were: 00.00-03.59 am, 04.00-07.59 am, 08.00-11.59 am, 00.00-03.59 pm, 04.00-07.59 pm, and 08.00-11.59 pm. Negative binomial regression models were used to calculate least-square means of admission cTnT concentrations with 95% confidence intervals (CIs). Results: A total of 19,460 patients were included with a mean age of 54 +/- 16 years. Patients who arrived during the night were younger, but other characteristics were similar among the time periods. The greatest mean admission cTnT concentrations for men (9.0 ng/l, 95% CI, 8.7-9.3), and women (8.0 ng/l, 95% CI, 7.8-8.2) were found at 08.00-11.59 am. After adjustment for age and estimated glomerular filtration rate, no significant diurnal variation in admission cTnT concentrations was observed. Conclusions: In a cohort of unselected patients with chest pain, and no acute condition affecting troponin admission concentrations, we found no evidence of clinically relevant diurnal variation in admission cTnT concentrations. There is no need to take the time point when blood is drawn into account in the assessment of admission cTnT concentrations in the ED.