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A new immunoassay (ELISA) based on an antiserum that preferentially recognizes the free form of the pyridinoline (Pyr) crosslink was used to assess the urinary excretion of Pyr in a large normal sample of the population comprising 236 men and 193 women 30-90 years of age. Urinary Pyr increased significantly with age in both sexes. In women Pyr was higher than in men (57 +/- 21 versus 46 +/- 17 nmol/mmol creatinine, p < 0.001), and the menopause was reflected by a mean 37% increase, from an average 43 to 59 nmol/mm creatinine (p < 0.001). In 52 patients with active Paget's disease of bone, Pyr excretion was markedly increased (206 +/- 160 nmol/mmol creatinine, p < 0.001 versus controls) and decreased by 71% after 3 days of IV treatment with the bisphosphonate pamidronate. Free Pyr measured by the ELISA and the total urinary excretion measured by HPLC were highly correlated both in normals (n = 74, r = 0.83, p < 0.001) and in Pagetic patients (n = 20, r = 0.93, p < 0.001). The mean intra- and interassay coefficients of variation of the ELISA were below 9 and 15%, respectively. It is concluded that this new convenient immunoassay of Pyr should be valuable for the clinical investigation of patients with osteoporosis and other metabolic bone diseases.
Delmas et al. (Sat,) studied this question.