Received on February 17, 2008
Accepted on June 30, 2008

Endocrinology and Metabolism

Automated HPLC Assay for Urinary Collagen Cross-links: Effect of Age, Menopause, and Metabolic Bone Diseases

¹ Division of Endocrinology, Diabetes and Clinical Nutrition, University Hospital CH-4031 Basel/Switzerland, and Endocrine Practice and Laboratory, Missionsstrasse 24, CH-4055 Basel/Switzerland
² Endocrine Practice and Laboratory, Missionsstrasse 24, CH-4055 Basel/Switzerland
³ Division of Metabolism & Molecular Pediatrics, University Children's Hospital, CH-8032 Zurich, Switzerland

^* To whom correspondence should be addressed. E-mail: marius.kraenzlin{at}unibas.ch.

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; Pagets 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.