There are two major components of screening for osteoporosis: assessment of risk factors and BMD measurement. Older age, low body mass index (BMI), and not using estrogen replacement are associated with increased risk of osteoporosis and fracture. Other risk factors include white or Asian ancestry, positive family history, tobacco use, and low levels of weight-bearing physical activity (Melton et al., 1989). The WHO FRAX is a common assessment tool.* Other specific instruments, such as the Osteoporosis Risk Assessment Instrument (ORAI) and the Simple Calculated Osteoporosis Risk Estimation (SCORE) tool, use these risk factors to identify women at increased risk for fracture or low BMD. The ORAI has sensitivity of 94% and specificity of 41%, and the SCORE has sensitivity of 91% and specificity of 40% (Nelson and Helfand, 2002).
The BMD measured at the femoral neck by dual-energy x-ray absorptiometry (DEXA) is the most validated predictor of hip fractures. Several other methods for measuring BMD include single-photon absorptiometry, ultrasound, quantitative CT, single-energy x-ray absorptiometry, and peripheral quantitative CT. The results between tests are not highly correlated with one another, and the likelihood of a diagnosis of osteoporosis varies greatly depending on the site and type
of test used, number of sites tested, brand of densitometer, and relevance of the reference range.
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