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 assessed in urine by high-performance liquid chromatography (HPLC) after acid hydrolysis and a prepurification step. Immunoassays have been developed to measure urinary Pyr directly. Here we developed and evaluated an enzyme-linked immunosorbent assay (ELISA), specific for the urinary free Pyr form, in normal adults and in patients with metabolic bone diseases. Urinary Pyr excretion increased significantly with age for men (r = 0.288; p < 0.001) and for women (r = 0.362; p < 0.001). An average 55% increase was noted between premenopausal (n = 41) and early postmenopausal (n = 42) women (mean +/- 1 SD; 22.4 +/- 6.3 nmol Pyr/mmol creatinine and 34.7 +/- 16.8 nmol Pyr/mmol creatinine, respectively; p < 0.001). High Pyr levels were found in patients with hyperthyroidism (n = 29; 126.5 +/- 84.2 nmol Pyr/mmol creatinine), Paget's disease of bone (n = 30; 61.8 +/- 45.8 nmol 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 correlated with urinary hydroxyproline, the conventional bone resorption marker (r = 0.87; p < 0.001), and with total alkaline phosphatase, a marker of bone formation (r = 0.55; p < 0.005). Free Pyr 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).(ABSTRACT TRUNCATED AT 250 WORDS)