THE ACCURACY OF PERIPHERAL SKELETAL ASSESSMENT AT THE RADIUS IN ESTIMATING FEMORAL BONE-DENSITY AS MEASURED BY DUAL-ENERGY X-RAY ABSORPTIOMETRY - A COMPARATIVE-STUDY OF SINGLE-PHOTON ABSORPTIOMETRY AND COMPUTED-TOMOGRAPHY

Objectives. One of the latest developments in bone densitometry is per ipheral quantitative computed tomography (pQCT), a method which allows the separate determination of cortical and trabecular bone mineral de nsity (BMD) in the peripheral skeleton. This study was designed to com pare the relative abilities of single-photon absorptiometry (SPA) and pQCT to reflect BMD of the proximal femur as measured by dual-energy X -ray absorptiometry (DXA), an established predictor of osteoporotic hi p fracture risk. Design, Cross-sectional study. Subjects. A well-defin ed community-based sample of 129 skeletally healthy women aged 70-87 y ears. Measurements. Radial BMD by SPA and pQCT and femoral BMD by DXA. Univariate and multivariate regression analyses were performed relati ng the DXA measurements at the femoral neck and the trochanteric regio n with the values of SPA and pQCT. Results. Approximately 38% of the v ariance in femoral neck BMD could be explained by BMD of the midradius assessed by SPA, in contrast to only 18-27% by pQCT. At the trochante r, 32% of BMD could be predicted by SPA as compared to 19-26% by pQCT. Moreover, according to multiple regression, prediction of femoral BMD by SPA was not enhanced by performing pQCT. Conclusions. Radial pQCT has little value as a screening tool to identify elderly women with lo w femoral BMD. Additional research is needed to determine whether or n ot pQCT will enhance fracture prediction beyond that obtainable from a density measurement by SPA.