title: Evaluation of urinary N-telopeptide of type I collagen measurements in the management of osteoporosis in clinical practice.
abstract: We measured urinary N-telopeptide of type I collagen (U-NTX) to monitor response to bisphosphonates for osteoporosis. Decrease in U-NTX was associated with increase in spine bone density. A lesser response in U-NTX was more likely in those with secondary osteoporosis or with poor compliance. U-NTX may be a useful early indicator of treatment non-compliance or secondary osteoporosis.
  
  
  BACKGROUND
  This study aims to determine the utility of the bone resorption marker, U-NTX, in the clinical setting, to monitor the response to bisphosphonate therapy (alendronate and risedronate) for osteoporosis.
  
  
  METHODS
  A retrospective evaluation of data collected as part of the bone turnover marker monitoring service in the Metabolic Bone Centre, Sheffield, UK. Treatment compliance, underlying causes of osteoporosis, change in U-NTX/creatinine (Cr) at 4 months and change in spine and hip bone mineral density (BMD) by dual-energy X-ray absorptiometry were recorded. Treatment response was defined as either a change in U-NTX/Cr greater than a pre-defined least significant change (LSC) of 54 % or to within the lower half of a pre-defined pre-menopausal reference interval (≤ 30 nM BCE/mmol Cr).
  
  
  RESULTS
  A greater decrease in U-NTX/Cr at 4 months was associated with a greater increase in spine BMD at 18 months (r = -0.33; P < 0.0001, Pearson's correlation). The mean U-NTX/Cr at 4 months was higher in patients with secondary osteoporosis compared with those with primary osteoporosis (P < 0.01, ANOVA). A lesser response in U-NTX/Cr increased the likelihood of secondary osteoporosis or poor treatment compliance (P = 0.04, Fisher's exact test). A lack of response in U-NTX/Cr to within the lower half of the reference interval was a better indicator of secondary osteoporosis and treatment non-compliance than a change in U-NTX/Cr greater than LSC.
  
  
  CONCLUSIONS
  Treatment monitoring using U-NTX/Cr has a place in clinical practice for the early identification of non-compliance or presence of secondary osteoporosis.
authors.affiliation: NIHR Musculoskeletal Biomedical Research Unit, Department of Human Metabolism, University of Sheffield, Sheffield, UK.
authors.forename: I
authors.initials: I
authors.lastname: Baxter
authors.forename: A
authors.initials: A
authors.lastname: Rogers
authors.forename: R
authors.initials: R
authors.lastname: Eastell
authors.forename: N
authors.initials: N
authors.lastname: Peel
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000652:urine; D015519:Bone Density / Q000187:drug effects / Q000502:physiology; D050071:Bone Density Conservation Agents / Q000627:therapeutic use*; D024042:Collagen Type I / Q000652:urine*; D004164:Diphosphonates / Q000627:therapeutic use; D016903:Drug Monitoring / Q000379:methods; D005260:Female; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008297:Male; D055118:Medication Adherence; D008875:Middle Aged; D010024:Osteoporosis / Q000188:drug therapy* / Q000503:physiopathology / Q000652:urine; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy / Q000503:physiopathology / Q000652:urine; D058866:Osteoporotic Fractures / Q000652:urine; D010455:Peptides / Q000652:urine*; D012189:Retrospective Studies; D017211:Treatment Failure
chemical_list: D015415:Biomarkers; D050071:Bone Density Conservation Agents; D024042:Collagen Type I; D004164:Diphosphonates; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide