REFERENCE RANGES OF BONE-MINERAL DENSITY FOR WOMEN IN SOUTHERN ENGLAND - THE IMPACT OF LOCAL DATA ON THE DIAGNOSIS OF OSTEOPOROSIS

The construction of reference ranges that accurately represent the pop ulation at large is essential for the correct identification of osteop orosis from bone mineral density (BMD) measurements. In this study, re ference data supplied by the manufacturer of the Lunar DPX + bone dens itometer were compared with data obtained locally. Lumbar spine, proxi mal femur and total body BMD measurements were made in an age-stratifi ed random sample of 702 Southampton women aged 20 to 89 years. Relevan t demographic and medical data were recorded for each subject using a questionnaire. Reference curves of BMD (mean +/- SD) were plotted agai nst age for each measurement site and were found to be higher than the manufacturer's reference values at all ages and sites. Exclusion of w omen with factors known to affect bone mass only served to increase th is discrepancy. According to World Health Organisation definitions, os teoporosis may be identified from BMD values alone. Based upon neck of femur BMD values, 100 (14.8%) of the women in this study group were c ategorized as osteoporotic using local young normal reference data, co mpared with only 39 (5.8%) using the manufacturer's data. By normalizi ng for age distribution, these findings were extrapolated to the local population where it was predicted that 26.0% and 10.1% of females ove r 50 years of age would be classified as osteoporotic using the respec tive reference ranges. This study clearly illustrates how the numbers of women diagnosed as osteoporotic vary with the use of different refe rence populations.