The British Journal of Radiology, Vol 68, Issue 812 903-909, Copyright © 1995 by British Institute of Radiology

ARTICLES

Dual energy X-ray absorptiometry normal reference range use within the UK and the effect of different normal ranges on the assessment of bone density

A Simmons, S Barrington, MJ O'Doherty and AJ Coakley
East Kent Osteoporosis Screening and Research Unit, Kent and Canterbury Hospitals NHS Trust, UK.

The number of different normal ranges used on dual energy X-ray absorptiometry (DEXA) machines in the United Kingdom was determined by means of a postal questionnaire. Both femoral neck and posteroanterior spine L2-L4 regions were considered. It was clear from this survey that a variety of normal ranges were in use for all manufacturers of DEXA systems. The effects of four normal ranges supplied by Norland for use within the UK on the stratification of over 1000 consecutive patients into different grades of bone mineral density (BMD) and Z-score were examined. The main outcomes measure the number of patients with BMD less than 80% of mean age-matched BMD and Z-score less than -1.5 over the femoral neck and spine for each normal range. The percentage of patients for each normal range with BMD less than 80% of mean for the femoral neck were 24.6%, 7.4%, 17.5% and 11.1% and for the spine 12.1%, 7.4%, 16.5% and 14.4%, respectively. For the femoral neck, 21.2%, 5.0%, 12.9% and 12.1% of patients had Z-scores of less than -1.5, for the spine this was 7.9%, 8.1%, 14.2% and 13.6% of patients. These differences between ranges are large enough to influence patient management--patients may be diagnosed as osteoporotic using one range and normal using another. The relationship between hip and spine measurements was also studied as some therapeutic agents do not affect BMD equally at all anatomical sites. The number of patients with a lower hip than spine BMD grade varied from 12.3% to 34.4%, and with a lower hip than spine Z-score from 14.0% to 43.4%. Choice of normal range thus has a critical effect on the categorization of osteoporotic patients using DEXA. The wide variety of normal ranges indicates that there are likely to be differences in patient management throughout the country. This will be an increasing problem due to the ability of NHS purchasers to switch contracts from one provider to another.

This article has been cited by other articles:

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				A. Simmons, S. Barrington, M. J O'Doherty, and A. J Coakley Bone mineral densitometry in clinical practice BMJ, November 11, 1995; 311(7015): 1300b - 1301. [Full Text]