Bone densitometry is not a good predictor of hip fracture

Bone densitometry is widely used in osteoporosis clinics to identify people at increased risk of fracture. Terence Wilkin and Devasenan Devendra believe that evidence for the efficacy of bone densitometry is weak, but Jan Dequeker and Frank P Luyten argue that their interpretation of the evidence is too narrow and that screening high risk patients is cost effective

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The World Health Organization defines osteoporosis as a “progressive systemic skeletal disease characterised by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture.”1 The low bone mass used to define osteoporosis is arbitrarily fixed at 2.5 standard deviations or more below the mean bone density for premenopausal women. Assessment of bone density provides a precise figure to which doctors and patients feel able to relate with confidence. We believe this confidence is unjustified.

By one definition, osteoporosis is an arbitrary point on a scale. By another, it is a pathological process of microarchitectural deterioration in which the unconstrained activity of bone osteoclasts accelerates bone resorption. The two definitions are fundamentally different. Accelerated bone resorprtion exists throughout postmenopausal life, whereas osteoporosis does not—and may never. Bone densitometry measures bone density, not bone turnover or bone stability. We have argued previously that bone turnover, rather than bone density, is the responsive element in treatments for preventing fractures.2 The pathology of osteoporosis is one of uncontrolled bone resorption and the treatment (whether hormone replacement therapy or bisphosphonates) antiresorptive. We present five evidence based reasons why the results of bone densitometry may not predict postmenopausal fracture of the hip in the way that many believe it to.