A New Approach to Osteoporosis and Fracture Risk
A new statistical model predicts 10-year risk for hip and other major fractures.
Bone-mineral density (BMD), expressed statistically as standard deviations above or below the BMD of a healthy young adult (T-scores), is used widely in making osteoporosis treatment decisions. However, it is only one of many factors that determine absolute risk for fracture.
Recognizing the limitations of relying on BMD alone, researchers have developed a new paradigm to address osteoporosis and its treatment. A research team sponsored by the World Health Organization (WHO) has analyzed data from nine population-based studies conducted worldwide and has created a statistical model that predicts 10-year risk for hip and other major fractures. The model, called "FRAX," incorporates BMD, age, sex, body-mass index, and seven other risk factors; a FRAX online calculator is available at http://www.shef.ac.uk/FRAX.
U.S. investigators performed a cost-effectiveness analysis of osteoporosis treatment using the same WHO data and additional U.S. data. The researchers calculated that 10-year risk for hip fracture should be at least 3% for treatment to be cost-effective. Their assumptions included a cost-effectiveness threshold of US$60,000 per quality-adjusted life-year, an annual cost of US$600 for a bisphosphonate drug, and a 35% reduction in fractures with treatment. In a second article, the same researchers constructed tables showing 10-year fracture risk as a function of risk factors and T-scores. For example, a white American woman with a T-score of –2.5, normal BMI, and no other risk factors would cross the treatment threshold of 3% 10-year risk around age 65. Similar calculations can be made using the online tool noted above.
Comment: This approach to osteoporosis treatment is analogous to using a Framingham 10-year risk score to make cholesterol drug therapy treatment decisions. Although one could quibble with some of the assumptions of the cost-effectiveness analysis, the approach is more rational than using T-scores alone or clinical intuition to make decisions about bisphosphonate therapy. The National Osteoporosis Foundation has embraced this paradigm in its new "Clinician’s Guide to Prevention and Treatment of Osteoporosis" (the three articles cited for this summary are available free of charge at this link to the foundation’s website).
— Allan S. Brett, MD
Published in Journal Watch General Medicine April 8, 2008
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