Background/Aims: Seasonal variations in laboratory test results have been pointed out in dialysis patients. Although the mechanism for this phenomenon is not clear, this could result in changes in dialysis and medication prescriptions. We investigated the effect of the circannual rhythm on laboratory test parameters in chronic haemodialysis patients. Methods: Data of 38 laboratory test parameters were collected every month and analyzed for 150 stable haemodialysis patients, with non-linear sine wave regression and paired t test between data of peak and trough months. Results: Serum urea nitrogen, unsaturated iron binding capacity, lactate dehydrogenase, alkaline phosphatase, amylase, and neutrophil count showed significant circannual rhythms with high amplitudes. Additionally, serum creatinine, uric acid, chloride, calcium, phosphate, magnesium, total cholesterol, total protein, leucocyte count, mean corpuscular haemoglobin level, mean corpuscular haemoglobin concentration, and platelet count showed significant circannual rhythms with little amplitudes. Conclusions: The circannual rhythm of laboratory test parameters could be attributed to seasonal variations in food intake. Awareness of these variations should be taken into account in the interpretation of laboratory results.
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