title: Automated HPLC assay for urinary collagen cross-links: effect of age, menopause, and metabolic bone diseases.
abstract: BACKGROUND
  The pyridinium cross-links pyridinoline (PYD) and deoxypyridinoline (DPD) are established markers of bone resorption. We evaluated the analytical and clinical performance of a commercially available PYD HPLC assay and established reference intervals in children and adults.
  
  
  METHODS
  We used a commercially available reagent set (Chromsystems Instruments & Chemicals) to measure PYD and DPD in 319 healthy controls (156 premenopausal women, 80 healthy men, and 83 healthy children age 1 month to 14 years) and 397 patients with metabolic bone diseases (postmenopausal osteoporosis, n = 175; male osteoporosis, n = 176; hyperparathyroidism, n = 17; hyperthyroidism, n = 19; Paget disease, n = 10).
  
  
  RESULTS
  The mean intraassay and interassay CVs were <6% and <8% for both PYD and DPD, respectively. The reference interval was constant for premenopausal women in the age group 20-49 years. In men, cross-link values peaked at 20-29 years and decreased thereafter. Women with postmenopausal osteoporosis had significantly higher PYD (51%) and DPD (58%) values compared to premenopausal women. Similar results were found in osteoporotic men. In children the highest values were found in the first weeks and months after birth, followed by a decrease of 50%-60% at age 11-14 years. In metabolic bone diseases cross-link concentrations were significantly increased. The DPD:PYD ratio (mean value approximately 0.2) was remarkably constant in all populations evaluated.
  
  
  CONCLUSIONS
  The automated HPLC assay is a precise and convenient method for PYD and DPD measurement. We established reference intervals for adult women and men and for children up to 14 years old. The cross-link concentrations we determined by use of this HPLC method confirm its clinical value in enabling identification of increased bone resorption in patients with metabolic bone diseases.
authors.affiliation: Division of Endocrinology, Diabetes, and Clinical Nutrition, University Hospital, CH-4031 Basel, Switzerland. marius.kraenzlin@unibas.ch
authors.forename: Marius E
authors.initials: ME
authors.lastname: Kraenzlin
authors.forename: Claude A
authors.initials: CA
authors.lastname: Kraenzlin
authors.forename: Christian
authors.initials: C
authors.lastname: Meier
authors.forename: Cecilia
authors.initials: C
authors.lastname: Giunta
authors.forename: Beat
authors.initials: B
authors.lastname: Steinmann
mesh_terms: D000328:Adult; D017677:Age Distribution; D001851:Bone Diseases, Metabolic / Q000652:urine*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003094:Collagen / Q000652:urine*; D005260:Female; D006262:Health; D006801:Humans; D008297:Male; D008593:Menopause / Q000652:urine*; D008875:Middle Aged
chemical_list: D003094:Collagen