Short- and long-term effects of ibandronate treatment on bone turnover in Paget disease of bone

Background: In Paget disease of bone (PD), serum total alkaline phosphatase (TAP) is a valid marker of disease activity. The aim of the present longit udinal study was to compare TAP with new and potentially more specific mark ers of bone turnover in bisphosphonate-treated patients with PD. Methods: Twenty patients with active PD were studied before and after treat ment with 2 mg of intravenous ibandronate over a period of 12 months. TAP ( by colorimetry), serum bone-specific alkaline phosphatase (BAP; by enzyme i mmunoassay), serum osteocalcin (OC; by ELISA), serum bone sialoprotein (BSP ; by RIA), and urinary total pyridinoline (PYD; by HPLC) and deoxypyridinol ine (DPD; by HPLC) were measured as markers of bone turnover. Results: Before treatment, TAP, BAP, and BSP were increased in all 20 patie nts, whereas OC was increased in 10, PYD in 13, and DPD in 15 patients. Thr ee months post treatment, nine patients showed normalized TAP values, and a greater than or equal to 25% re-increase (i.e., relapse) was observed in a ll patients after 12 months. A normalization of BAP was achieved in six pat ients only. No significant changes were found for OC. BSP was decreased sig nificantly at 24 h, and DPD at 48 h post treatment. A normalization of BSP was found in 8, of PYD in 18, and of DPD in 16 cases. Both PYD and DPD incr eased significantly from 9 months post treatment onward. Conclusions: Most markers of bone turnover show similar long-term changes a fter treatment of active PD with ibandronate. With regard to cost-effective ness and assay performance, TAP remains the marker of choice in therapeutic monitoring of PD. However, more specific markers may improve the biochemic al assessment of PD in certain situations. (C) 2000 American Association fo r Clinical. Chemistry.