title: Circannual rhythm of laboratory test parameters among chronic haemodialysis patients.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Laboratory Medicine, Nihon University School of Medicine, Tokyo, Japan. myanai@med.nihon-u.ac.jp
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Yanai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Satomura
authors.forename: Yuki
authors.initials: Y
authors.lastname: Uehara
authors.forename: Masaya
authors.initials: M
authors.lastname: Murakawa
authors.forename: Makoto
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Kazunari
authors.initials: K
authors.lastname: Kumasaka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001774:Blood Chemical Analysis; D019411:Clinical Laboratory Techniques; D004435:Eating; D005260:Female; D006403:Hematologic Tests; D006801:Humans; D007676:Kidney Failure, Chronic; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis; D012621:Seasons