Rhythmic 24-hour variations of frequently used clinical biochemical parameters in healthy young males--the Bispebjerg study of diurnal variations.

PURPOSE

To evaluate the influence of time of day on the circulating concentrations of 14 frequently used clinical biochemical parameters in the Bispebjerg study of diurnal variations.

MATERIALS AND METHODS

Venous blood samples were obtained under controlled environmental, activities and food conditions from 24 healthy young men every third hour through 24 hours, nine time points in total. At each time point, the parameters' concentrations were measured. The data were analyzed by rhythmometric statistical methods and in addition the biological variations were calculated.

RESULTS

Significant oscillation of melatonin with an amplitude (amp) of 19.84 pg/ml and a peak at 03:34 h confirmed the normal 24-hour rhythms of the participants. Potassium (p < 0.0001, amp = 0.18 mmol/L), sodium (p < 0.0001, amp = 1.10 mmol/L) creatine kinase (p = 0.01, amp = 17.18 U/L), bilirubin (p < 0.0001, amp = 2.36 μmol/L) and aspartate aminotransferase (p < 0.0001, amp = 1.66 U/L) oscillated with gradually falling mean concentrations through the day to nadir around midnight. Urea nitrogen (p = 0.01, amp = 0.22 mmol/L) oscillated with gradually increasing mean concentrations through the day peaking around midnight. Lactate dehydrogenase (p < 0.0001, amp = 9.76 U/L) oscillated with gradually increasing concentrations through the early day peaking in the afternoon. Uric acid (p = 0.03, amp = 0.013 mmol/L) oscillated with gradually increasing concentrations through the night peaking in the morning. Potassium and sodium had the highest 24-hour oscillations in proportion to the reference intervals of the parameters for healthy young men.

CONCLUSIONS

In the clinical setting, diurnal variations of clinical biochemical parameters commonly used through the day and night must be considered when concentration changes in the parameters are evaluated especially potassium and sodium.