title: Serum concentrations of cross-linked N-telopeptides of type I collagen: new marker for bone resorption in hemodialysis patients.
abstract: BACKGROUND
  Urinary cross-linked N-telopeptide of type I collagen (NTX) is a reliable bone resorption marker in patients with metabolic bone disease. We assessed a clinically available serum NTX assay suitable for anuric patients on hemodialysis (HD).
  
  
  METHODS
  Serum concentrations of NTX, C-terminal telopeptide of type I collagen (beta-CTX), pyridinoline (PYD), and deoxypyridinoline (DPD) were determined as bone resorption markers, and those of bone alkaline phosphatase (BAP) and intact osteocalcin (OC) as bone formation markers, in 113 male HD patients (mean age, 59.3 years; mean HD duration, 67.7 months). Each patient's bone mineral density (BMD) in the distal third of the radius was measured twice, with a 2-year interval between measurements, by dual-energy x-ray absorptiometry.
  
  
  RESULTS
  Serum NTX correlated significantly with beta-CTX, PYD, DPD, BAP, and intact OC. NTX, as well as beta-CTX, PYD, DPD, BAP, and intact OC, correlated significantly with BMD at the time of measurement. NTX, beta-CTX, and DPD correlated significantly with the annual change in BMD during the 2-year period thereafter, in contrast to PYD, BAP, and intact OC. Patients in the highest quartile of serum NTX concentrations showed the fastest rate of bone loss. The sensitivity and specificity for detecting rapid bone loss were 48% and 83%, respectively, for serum NTX.
  
  
  CONCLUSIONS
  Serum NTX may provide a clinically relevant serum assay to estimate bone turnover in HD patients.
authors.affiliation: Department of Metabolism, Endocrinology and Molecular Medicine, Osaka City University Graduate School of Medicine, Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Maeno
authors.forename: Masaaki
authors.initials: M
authors.lastname: Inaba
authors.forename: Senji
authors.initials: S
authors.lastname: Okuno
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamakawa
authors.forename: Eiji
authors.initials: E
authors.lastname: Ishimura
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Nishizawa
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001862:Bone Resorption / Q000097:blood*; D003094:Collagen / Q000097:blood*; D024042:Collagen Type I; D006801:Humans; D008875:Middle Aged; D010455:Peptides / Q000097:blood*; D006435:Renal Dialysis; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D003094:Collagen