Clinical application of immunoassay for urinary total excretion of deoxypyridinoline in patients with osteoporosis

Urinary excretion of pyridinium cross-links is one of the biochemical markers for bone resorption in metabolic bone diseases. Efficacy of immunoassay for deoxypyridinoline (D-pyr) for monitoring effects of antiresorptive therapy was evaluated in 44 women with osteoporosis, including 4 patients with asymptomatic primary hyperparathyroidism. Urinary free forms and protein-bound (conjugated) forms of D-pyr were measured totally by a modified enzyme-liked immunoabsorbent assay (ELISA; PYRILINKS-DTM, Metra Biosystem, Mountain View, CA, USA), which required prehydrolysis of urine samples and adequate acidity adjusted with alkali. There was a close relationship between total excretion of D-pyr measured by reverse-phase high performance liquid chromatography (HPLC) and that measured by ELISA. In 27 patients, the percent change of urinary D-pyr by ELISA following hormone replacement therapy (HRT) was similar to that of urinary total forms of D-pyr using HPLC at the end of the first third, and sixth month. In 8 patients whose series of urine samples were corrected following HRT, the percent change of urinary total excretion of D-pyr by ELISA at the end of the third month was approximately −40%, significantly greater than that of excretion of free forms of D-pyr measured by ELISA (−30%;P