title: Bone-specific alkaline phosphatase concentrations are less variable than those of parathyroid hormone in stable hemodialysis patients.
abstract: Abnormalities of bone mineral metabolism and vascular calcification are prevalent in patients with kidney failure. Clinical management is based on biochemical targets, in particular parathyroid hormone (PTH) concentrations, but this has many limitations including high biological variation. A possible alternative is bone-specific alkaline phosphatase (ALP); therefore, we evaluated the biological variation of this marker in patients undergoing hemodialysis. Bone ALP was measured in non-fasting serum samples taken twice a week over a 6-week period in 22 stable hemodialysis patients and 12 healthy volunteers. The within-individual coefficients of variance were calculated and used to derive the critical difference required to be certain that an observed change was significant. The coefficient of variance for bone ALP was significantly higher in hemodialysis patients compared to healthy individuals. Seven samples were required to estimate the homeostatic set point of bone ALP, within 10%, in a hemodialysis patient. The concentration of serial bone ALP measurements would need to change by 36% between any two measurements before it can be considered a significant change. Since the biological variation of bone ALP is less than half that reported for PTH, our study provides further support for the use of bone ALP as an alternative marker of bone mineral metabolism in the setting of chronic kidney disease-mineral and bone disorder.
authors.affiliation: Clinical Biochemistry, East Kent Hospitals University NHS Foundation Trust, Kent and Canterbury Hospital, Canterbury, UK.
authors.forename: Sunita
authors.initials: S
authors.lastname: Sardiwal
authors.forename: Clare
authors.initials: C
authors.lastname: Gardham
authors.forename: Adrian E
authors.initials: AE
authors.lastname: Coleman
authors.forename: Paul E
authors.initials: PE
authors.lastname: Stevens
authors.forename: Michael P
authors.initials: MP
authors.lastname: Delaney
authors.forename: Edmund J
authors.initials: EJ
authors.lastname: Lamb
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D001851:Bone Diseases, Metabolic / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D016723:Bone Remodeling; D001842:Bone and Bones / Q000201:enzymology*; D016022:Case-Control Studies; D004739:England; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D011237:Predictive Value of Tests; D006435:Renal Dialysis / Q000009:adverse effects; D051437:Renal Insufficiency / Q000097:blood / Q000150:complications / Q000628:therapy*; D015203:Reproducibility of Results; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; C470125:PTH protein, human; D010281:Parathyroid Hormone; D000469:Alkaline Phosphatase