Monitoring treatment for osteoporosis by using bone densitometry.

In recent years, the range of treatments available for patients with osteoporosis has greatly increased. A decade ago, the only proven therapy was estrogen, but today the choices include bisphosphonates, selective estrogen-receptor modulators, calcitonin, and parathyroid hormone. Clinical trials involving bone mineral density (BMD) scans of the spine and femur have had an important role in the evaluation of these new therapies. In particular, the efficacy of treatments has now been verified in large studies powered to show reductions in fracture risk. In contrast with the use of BMD scans in research studies, their value for monitoring response to treatment in individual patients is less certain. In many cases, the increases in BMD are too small to reliably distinguish between true changes and measurement error. However, experience with estrogen and bisphosphonates suggests that these treatments have a beneficial effect on bone in most patients. Follow-up scans for patients taking these agents are therefore of limited value, apart from offering reassurance to the patient and the doctor. However, when new therapies are first introduced, follow-up scans have a useful role in building up the physician's experience and confidence.