title: Total and bone-specific alkaline phosphatase are associated with bone mineral density over time in end-stage renal disease patients starting dialysis.
abstract: BACKGROUND
  Alkaline phosphatase (ALP) and bone-specific ALP (BALP) are implicated in the abnormal skeletal mineralization and accelerated vascular calcification in chronic kidney disease (CKD) patients. Whereas ALP and BALP may predict mortality in CKD, BALP is reported to have higher sensitivity and specificity than total ALP in reflecting histological alterations in bone; however, results on their associations with bone mineral density (BMD) are inconsistent. Here we evaluated associations of total ALP and BALP with BMD during up to 24 months in end-stage renal disease (ESRD) patients.
  
  
  METHODS
  In this longitudinal study, 194 ESRD patients (median age 57 years, 66 % male, 32 % diabetes mellitus, mean body mass index 24.8 kg/m2) underwent measurements of total ALP and BALP and total and regional body BMD (by dual-energy X-ray absorptiometry) at dialysis initiation (n = 194), and after 12 (n = 98) and 24 months (n = 40) on dialysis.
  
  
  RESULTS
  At baseline, patients had median total ALP 65.4 (43.3-126.4) U/l, BALP 13.5 (7.1-27.3) µg/l and BMD 1.14 (0.97-1.31) g/cm2. During the study period, serum concentrations of ALP and BALP increased significantly (p < 0.001), whereas total and regional BMD remained stable. BMD correlated inversely with total ALP (rho = -0.20, p = 0.005) and BALP (rho = -0.30, p < 0.001) at baseline, and correlations were similar also at 12 and 24 months.
  
  
  CONCLUSIONS
  ALP and BALP are equally accurate albeit weak predictors of BMD in ESRD patients, both at baseline and longitudinally. The dissociation between stable BMD and increasing ALP and BALP may possibly reflect increased soft tissue calcifications with time on dialysis.
authors.affiliation: Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Hospital Huddinge, Karolinska University, KFC, Novum, 141 86, Stockholm, Sweden.
authors.forename: Annelie
authors.initials: A
authors.lastname: Bergman
authors.affiliation: Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Hospital Huddinge, Karolinska University, KFC, Novum, 141 86, Stockholm, Sweden.
authors.forename: Abdul Rashid
authors.initials: AR
authors.lastname: Qureshi
authors.affiliation: Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Hospital Huddinge, Karolinska University, KFC, Novum, 141 86, Stockholm, Sweden.
authors.forename: Mathias
authors.initials: M
authors.lastname: Haarhaus
authors.affiliation: Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Hospital Huddinge, Karolinska University, KFC, Novum, 141 86, Stockholm, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Lindholm
authors.affiliation: Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Hospital Huddinge, Karolinska University, KFC, Novum, 141 86, Stockholm, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Barany
authors.affiliation: Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Hospital Huddinge, Karolinska University, KFC, Novum, 141 86, Stockholm, Sweden.
authors.forename: Olof
authors.initials: O
authors.lastname: Heimburger
authors.affiliation: Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Hospital Huddinge, Karolinska University, KFC, Novum, 141 86, Stockholm, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Stenvinkel
authors.affiliation: Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Hospital Huddinge, Karolinska University, KFC, Novum, 141 86, Stockholm, Sweden. bjorn.anderstam@ki.se.
authors.forename: Björn
authors.initials: B
authors.lastname: Anderstam
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000469:Alkaline Phosphatase / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D015519:Bone Density; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis; D006435:Renal Dialysis; D013997:Time Factors; D016896:Treatment Outcome; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; D000469:Alkaline Phosphatase
keywords: Alkaline phosphatase; Bone mineral density; Bone-specific alkaline phosphatase; Cardiovascular disease; Chronic kidney disease