A Comparison of DXA Measurement of Lumbar Spine and Femoral Neck for Premenopausal Women

This study is used to compare the bone mineral density (BMD) of lumbar spine (LS) and femur neck (FN) for premenopausal women. The BMD measurements using dual energy x-ray absorptiometry technique (DXA) have been performed at Isfahan Osteoporosis Diagnosis Center since March 2002. Among the referred subjects 185 premenopausal women who had no known history of disease or taking any medication that affects BMD were selected. The long-term reproducibility (coefficient of variation, CV) of the DXA scanner for BMD measurements during the study period was assessed, using the phantom provided by the manufacturer. A Norland XR46 system was used for the investigations. The mean BMD for the FN and LS were found to be 0.859 ± 0.136 and 1.012 ± 0.161, respectively. The long-term BMD for LS and FN had a coefficient of variation of 1.0 and 1.2%, respectively. Discussion and Although a lower BMT T-score has been reported for LS compared to FN for women, the result obtained in this study shows a significantly lower BMT mean T-score (t = -9.02, p<0.0001) for FN. The BMD T-score of -0.551 ± 0.99 SD and -1.09 ± 1.17 SD was found for LS and FN, respectively. This finding is inconsistent with the previously reported results, which may be due to the physiological and life-style factors. Therefore, further research is required to determine the reason(s).