Bone densitometry Is a valuable investigationBMJ 1994; 308 doi: https://doi.org/10.1136/bmj.308.6943.1567 (Published 11 June 1994) Cite this as: BMJ 1994;308:1567
- J E Compston
EDITOR, - Susan M Ott draws attention to some of the potential pitfalls associated with the use of bone densitometry in clinical practice.1 Though I acknowledge that caution is needed in interpreting measurements of bone density, their value should not be understated. In particular, distinction should be made between the assessment of risk in an individual person and that in population screening. Because of the gaussian distribution of bone density and the gradient of the risk of fracture over its whole range, the proportional contribution to the total incidence of fracture of those with the lowest bone density is small; a major impact on the incidence can be achieved only by increasing bone density across the whole population. In clinical practice, however, the risk in an individual person is an important factor in decisions about treatment, based on analysis of the risk of disease on the one hand and the ratio of risk to benefit associated with treatment on the other. The present lack of strict densitometric criteria for treatment does not invalidate this approach, particularly for those at high risk.
The figure of around 6% quoted for the precision of bone densitometry is misleading since it applies only to Ward's triangle; for other regions of the femur, such as the femoral neck and trochanter, precision of 3% …