Use of bone alkaline phosphatase to monitor alendronate therapy in individual postmenopausal osteoporotic women.

BACKGROUND Biochemical bone markers are sensitive to the changes in bone turnover that result from treatment of postmenopausal osteoporotic women with antiresorptive therapies. Although information is available on the use of bone markers in monitoring therapy in groups of subjects, less is known regarding how these markers perform in individual patients. METHODS Serum bone alkaline phosphatase (bone ALP) concentrations, measured with the Tandem(R) Ostase(R) assay, were used to monitor the biochemical response of bone in postmenopausal women with osteoporosis receiving either 10 mg/day alendronate therapy (n = 74) or calcium supplementation (n = 148) for 24 months. RESULTS Bone ALP decreased significantly from baseline at 3 months (P </=0.0001), reaching a nadir between 3 and 6 months of alendronate therapy. The magnitude of the bone ALP decrease in the treated osteoporotic population was consistent with normalization to premenopausal concentrations. Of the 74 alendronate-treated subjects, 63 (85.1%) demonstrated a decrease from baseline in bone ALP by 6 months that exceeded the least significant change of 25%. The bone ALP decrease from baseline exceeded 25% in 72 (97%) by the end of the study. CONCLUSION The bone ALP assay is a sensitive and reliable tool that may be used to monitor the reduction in bone turnover after alendronate therapy in individual postmenopausal osteoporotic women.