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Osteodensitometry is the standard method for measuring bone mineral density. Since the 1990s, diagnosis of osteoporosis has been defined, by convention, by a bone density T score cutoff of < -2.5. This threshold, based on population statistics, is appropriate for the diagnosis of osteoporosis in Caucasian postmenopausal women in Europe and North America but may not be suitable for other populations.

To determine whether measurement of bone mineral density is useful in the prevention of fractures in postmenopausal women, we reviewed the relevant literature using our established in-house methodology.

Two meta-analyses of cohort followup studies involving tens of thousands of women showed a statistically increased risk of fracture in women with low bone density, especially in those with osteoporosis diagnosed by means of osteodensitometry.However,the majority of postmenopausal fractures occur in women without osteoporosis.

Routine bone density measurement has no proven impact on fracture prevention.

Some drugs designed for primary fracture prevention have been tested in postmenopausal women selected on the basis of their bone mineral density. In these patients, alendronic acid and raloxifene were both effective in the prevention of asymptomatic vertebral fractures: about 2 fractures prevented per 100 women treated for 3 to 4 years. A rather shaky retrospective subgroup analysis suggests that alendronic acid can also prevent symptomatic fractures in women with osteoporosis diagnosed by means of osteodensitometry.The data are too fragile to justify routine screening for osteoporosis in postmenopausal women, or exposing large numbers of women to the adverse effects of these drugs.

Severe osteoporosis in postmenopausal women is defined by the presence of both low bone mineral density and a history of fragility fractures following low-energy trauma. Alendronic acid is the best-assessed drug in these women,preventing about 3 symptomatic vertebral fractures and 1 hip fracture when 100 patients are treated for 3 years. After a first fracture, women should be asked questions designed to assess the severity of the trauma, and should undergo osteodensitometry to document osteoporosis before exposure to the potential adverse effects of bisphosphonates.

©Prescrire April 2008

Source: Prescrire International April 2008; 17 (94): 68-72.

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