Biological variation and reference change value of serum bone markers in hemodialysis patients

Aim: Biological variation (BV) describes the variation in constituents regulated by homeostatic processes in the body. There is an extensive literature concerning BV of analytes which has been reported in healthy subjects. However, in the patients with ongoing pathological conditions such as chronic renal failure, the BV of analytes may not be the same as healthy subjects. The aim of this study was to calculate; within-subject BV (CVI), between-subject BV (CVG), index of individuality (II) and reference change values (RCV) of serum bone markers in hemodialysis patients. Materials and Methods: Totally five serum specimens were obtained from each 30 stabil hemodialysis patients (15 female and 15 male) in an interval of one week period. Serum Alkaline Phosphatase (ALP), Acid Phosphatase (ACP), Osteocalcin (OC), β-CrossLaps (CTX), Calcium (Ca+2), Phosphat (P), Parathyroid hormone (PTH) and Vitamin D levels of these patients were analyzed. ANOVA tests were used to calculate the variations. Results: The CVI of ALP, ACP, OC, CTX, Ca+2, P, PTH and Viatamin D were found 10,9%, 5,6%, 15,1%, 1%, 0,6%, 1,1%, 45,7% and 2,4% respectively. The II of ALP, OC and vitamin D were found < 0,6. RCV were calculated as 32%, 45% and 10%, respectively for those analytes which were showed high individuality. RCV of ACP, CTX, Ca+2, P and PTH were calculated 20%, 3%, 1,8%, 3,2% and 127%, respectively. II of all these analytes were found > 0,6. Conclusion: Using RCV concept for predicting the renal osteodystrophy status of hemodialysis patients represents an optimization of laboratory reporting and could be a valuable tool for clinical decision. Keywords: Biological Variation, Reference Change Value, Analytical Quality Specifications, Serum Bone Markers, Hemodialysis.