ASSESSMENT OF URINARY PYRIDINOLINE EXCRETION WITH A SPECIFIC ENZYME-LINKED-IMMUNOSORBENT-ASSAY IN NORMAL ADULTS AND IN METABOLIC BONE-DISEASES

Pyridinoline (Pyr), a specific bone resorption marker, is usually asse ssed in urine by high-performance liquid chromatography (HPLC) after a cid hydrolysis and a prepurification step, Immunoassays have been deve loped to measure urinary Pyr directly, Here we developed and evaluated an enzyme-linked immunosorbent assay (ELISA), specific for the urinar y free Pyr form, in normal adults and in patients with metabolic bone diseases, Urinary Pyr excretion increased significantly with age for m en (r = 0.288; p < 0.001) and for women (r = 0.362; p < 0.001). An ave rage 55% increase was noted between premenopausal (n = 41) and early p ostmenopausal (n = 42) women (mean +/- 1 SD; 22.4 +/- 6.3 nmol Pyr/mmo l creatinine and 34.7 +/- 16.8 nmol Pyr/mmol creatinine, respectively; p < 0.001). High Pyr levels were found in patients with hyperthyroidi sm (n = 29; 126.5 +/- 84.2 mnol Pyr/mmol creatinine), Paget's disease of bone (n = 30; 61.8 +/- 45.8 mnol Pyr/mmol creatinine), and primary hyperparathyroidism (n = 10; 57.4 +/- 23.9 nmol Pyr/mmol creatinine). In patients with Paget's disease, urinary free Pyr excretion was corre lated with urinary hydroxyproline, the conventional bone resorption ma rker (r = 0.87; p < 0.001), and with total alkaline phosphatase, a mar ker of bone formation (r = 0.55; p < 0.005). Free 41 measured by ELISA was highly correlated with total Pyr and with total deoxypyridinoline HPLC measurements in postmenopausal women (n = 35; r = 0.94 and 0.91, respectively) and in patients with metabolic bone diseases (n = 22; r = 0.91 and 0.88, respectively; p < 0.001). This specific ELISA for fr ee Pyr is a convenient alternative to the HPLC analysis of free Pyr, a nd could be useful for bone resorption assessment in patients with met abolic bone diseases.