Assessment of fracture risk from bone mineral density and bone markers

The diagnosis of osteoporosis has been established by a WHO group as a bone mineral density (BMD) value that lies <–2.5 SD below the average value for young adult women. 1 The use of the T-score is most appropriate for dual energy X-ray absorptiometry (DXA) at the hip. 2 The use of the T-score alone for risk assessment is, however, problematic, since absolute risk for any T-score varies with age. Moreover, other risk factors also contribute to risk independently of age and BMD. Examples include the measurement of ultrasound and biochemical estimates of bone turnover. Other strong risk factors are age, body mass index, maternal family history of hip fractures and prior fragility fractures. A combination of these can be used to estimate long-term risks of hip fractures or other fractures to determine who should be treated. This chapter describes the principles of combining risk factors, with particular reference to the biochemical markers.