Letters

Developing a policy on osteoporosis

EDITOR,--I wish to comment on one aspect of the debate on the prevention of osteoporosis.¹ Implicit in much current thinking is the view that dual energy x ray absorptiometry of the spine and hip is the method of choice for bone densitometry. The Advisory Group on Osteoporosis, for example, provided details only of the number of installations for this method in Britain. Those unfamiliar with the subject may assume that this is the only reputable type of densitometry.

I see many patients who, rightly or wrongly, have become concerned about the possibility of crippling osteoporosis in the future. Such patients should have bone densitometry to reassure them or to encourage them to take hormone replacement therapy. Others are referred after being told, often on inadequate evidence, that their symptoms result from osteoporosis. These patients, too, need densitometry to move their further investigation and treatment in a more rational direction. Do all these patients need dual energy x ray absorptiometry of the spine and hip?

If the object is to predict the overall risk of fracture then dual energy x ray absorptiometry of the hip and the spine has proved less effective than single photon absorptiometry of the calcaneus or distal radius.² It is often suggested that densitometric measurements should be made of only the "clinically relevant" parts. For assessments of the risk of vertebral fracture, however, dual energy x ray absorptiometry of the spine was found to be less effective than various measurements of the calcaneus, metacarpals, or phalanges and of similar effectiveness to densitometry of the distal radius.³ For assessments of the risk of hip fracture dual energy x ray absorptiometry of the upper femur was superior to other methods in one study but not in others, in which it was equalled or surpassed by ultrasonography of the calcaneus or densitometry of the distal radius.^{2 4}

It is often forgotten that dual energy x ray absorptiometry of the spine is subject to interference from osteoarthritis, aortic calcification, and fractures; precision falls rapidly with age.⁵ Simpler methods of peripheral densitometry have good precision at all ages. Such methods may not only be more clinically appropriate but, being cheaper, allow more patients to be scanned for the same expenditure. The constant repetition, almost as a mantra, that dual energy x ray absorptiometry is the gold standard in densitometry should be questioned for the sake of both patients and taxpayers.

Honorary consultant Ninewells Hospital and Medical School, Dundee DD1 9SY

Colin R Paterson 

1. Sheldon TA, Raffle A, Watt I, Barlow D, Cooper C, Reeve J, et al. Department of Health shoots itself in the foot. BMJ 1996;312:296-8. (3 February.) [Free Full Text]
2. Melton LJ, Atkinson EJ, O'Fallon WM, Wahner HW, Riggs BL. Long term fracture prediction by bone mineral assessed at different skeletal sites. J Bone Miner Res 1993;8:1227-33. [Medline]
3. Ross P, Huang C, Davis J, Imose K, Yates J, Vogel J, et al. Predicting vertebral deformity using bone densitometry at various skeletal sites and calcaneus ultrasound. Bone 1995;16:325-32. [Medline]
4. Schott AM, Weill-Engerer S, Hans D, Duboeuf F, Delmas PD, Meunier PJ. Ultrasound discriminates patients with hip fracture equally well as dual energy x-ray densitometry and independently of bone mineral density. J Bone Miner Res 1995;10:243. [Medline]
5. Von der Recke P, Hansen MA, Overgaard K, Christiansen C. The impact of degenerative conditions in the spine on bone mineral density and fracture risk prediction. Osteoporos Int 1996;6:43-9. [Medline]