title: [Bone biomarkers in haemodialysis patients: bone alkaline phosphatase or ß-Crosslaps?].
abstract: BACKGROUND
  Bone turnover (BT) abnormalities are frequently observed in patients with chronic kidney disease. Bone biopsy remains the gold standard for diagnosis; however, its invasive nature has led to its decreased utilisation. The serum parathyroid hormone (PTH) level is not a reliable bone marker (BM) for BT assessment. The latest international recommendations suggest the use of total alkaline phosphatase (t-ALP) or bone-specific alkaline phosphatase (b-ALP), but not ß-CrossLaps (CTX). We compared b-ALP, t-ALP, and CTX levels in patients on haemodialysis (HD).
  
  
  METHODS
  All HD patients at a single institution following a standard 3×4 to 3×5 hours schedule were included in the study, provided they were free from liver disease. Serum intact PTH, t-ALP, b-ALP, and CTX values were compared at baseline and after 18 months of treatment. A kinetic study was performed for pre- and postdialysis CTX values over a 2-week period. We described the longitudinal evolution of these BMs in two typical patients.
  
  
  RESULTS
  A total of 98 patients on HD (46% female) were evaluated. The mean age was 69.8±11 years and the mean duration of dialysis was 54.4±61 months. At baseline, CTX (2.1±1 μg/L) correlated well with b-ALP (18±11 μg/L; r=0.64; P<0.001) and PTH (221±165 pg/mL; r=0.62; P<0.001). The changes in these values at 18 months were also correlated (ΔCTX compared with Δb-ALP: r=0.51; P<0.001; Δb-ALP compared with ΔPTH: r=0.37, P<0.01). b-ALP and t-ALP (245±132 U/L) were closely correlated (r=0.78), as was their variation over 18 months (r=0.67), but t-ALP did not correlate with PTH, and correlated poorly with CTX (r=0.38). The CTX reduction ratio during standard dialysis was approximately 70 to 75% over each session, although predialysis values remained stable.
  
  
  CONCLUSIONS
  In HD patients, mean CTX values are five times higher than the normal range. CTX appears to be an alternative to b-ALP for assessing BT. b-ALP remains the standard BM, despite being expensive, infrequently available in many laboratories, and not useful for patients with liver disease.
authors.affiliation: NEPHROCARE Tassin-Charcot, 7, avenue du Maréchal-Foch, 69110 Sainte Foy-Les-Lyon, France. guillaume-jean-crat@wanadoo.fr
authors.forename: Guillaume
authors.initials: G
authors.lastname: Jean
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Souberbielle
authors.forename: Samuel
authors.initials: S
authors.lastname: Granjon
authors.forename: Christie
authors.initials: C
authors.lastname: Lorriaux
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Hurot
authors.forename: Brice
authors.initials: B
authors.lastname: Mayor
authors.forename: Patrik
authors.initials: P
authors.lastname: Deleaval
authors.forename: Charles
authors.initials: C
authors.lastname: Chazot
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000469:Alkaline Phosphatase / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D016723:Bone Remodeling; D001842:Bone and Bones / Q000201:enzymology*; D003094:Collagen / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D011446:Prospective Studies; D006435:Renal Dialysis / Q000706:statistics & numerical data*; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000628:therapy
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone; D010446:Peptide Fragments; C110762:glutamyl-lysyl-alanyl-histidyl-aspartyl-glycyl-glycyl-arginine; D003094:Collagen; D000469:Alkaline Phosphatase