Uses and Limitations of Bone Mineral Density Measurements in the Management of Osteoporosis

Ralph E. Small, PharmD

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In This Article

Abstract and Introduction

Context: Bone mineral density (BMD) is used to diagnose osteoporosis, and often to measure efficacy in osteoporosis treatment trials; however, there is a poor correlation between lumbar spine BMD increases and vertebral fracture risk reduction in patients receiving treatment for osteoporosis.
Objective: The purpose of this article is to review the uses and limitations of BMD measurements and the relationship between BMD and bone strength.
Data Source/Study Selection: A MEDLINE literature search was conducted with the terms bone mineral density , fracture , osteoporosis , and bone strength as well as the generic names of osteoporosis therapies (alendronate, risedronate, raloxifene, teriparatide, and calcitonin). Search results were limited to English language journals and articles published within the last 20 years. Published abstracts from scientific meetings were also reviewed.
Conclusion: BMD measurement remains the most useful diagnostic tool for identifying patients with osteoporosis. Although they are helpful in guiding decisions to initiate osteoporosis treatment, subsequent changes in BMD provide an imperfect indicator of treatment efficacy. Analyses of clinical trials show an inconsistent relationship between increased spinal BMD and a decreased risk of vertebral fracture. Increased BMD accounts for less than 25% of the overall reduction in fracture risk in most instances. Consequently, fracture risk reduction itself remains the most clinically relevant therapeutic outcome of osteoporosis therapy.

Bone mineral density (BMD) is widely used for diagnosing osteoporosis and determining the need for therapy in patients at risk, as well as for monitoring individual patients' responses to therapy. It is often used as a surrogate measure of efficacy in clinical trials of osteoporosis therapies. Although there is a consensus that osteoporosis trials with fracture incidence as a primary end point provide the most meaningful assessment of drug efficacy, these trials typically require large numbers of patients and often take at least 3 years to generate adequate data.[1] Because every patient has a BMD measurement but not every patient experiences a fracture, trials with BMD as a surrogate end point require fewer patients and can be completed in less time and at a lower cost than studies that assess fracture as an end point. However, the effect of antiresorptive drugs on BMD accounts for only a small portion of the overall reduction in fracture risk.[2,3] For example, the proportion of the reduction in vertebral fracture risk from the Fracture Intervention Trial (FIT) showed that improvement in spinal BMD explained only 16% of the risk reduction of vertebral fracture with alendronate therapy.[2]

This article reviews the uses and limitations of BMD measurements and the relationship between BMD and bone strength. A MEDLINE literature search was conducted with the terms bone mineral density , fracture , osteoporosis , and bone strength as well as the generic names of osteoporosis therapies (alendronate, risedronate, raloxifene, teriparatide, and calcitonin). Search results were limited to English language journals and articles published within the last 20 years. Published abstracts from scientific meetings were also searched to obtain more recent analyses on the relationship between BMD and fracture.

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