Bone mineral density in the lumbar spine as determined by dual-energy X-ray absorptiometry - Comparison of whole-body scans and dedicated regional scans

Purpose: To compare bone mineral in the lumbar spine as measured by either consecutive regional or whole-body dual-energy X-ray absorptiometry (DXA), and to develop models that predict regional results from whole-body results. Material and Methods: In 180 children and young adults, bone mineral in the lumbar spine was measured by a Hologic QDR-1000/W DXA scanner, using either whole-body software (which can give data for the lumbar spine subregion) or dedicated lumbar spine software. Data on 139 persons were used to compare the two methods and to develop models that predict the result of a regional scan from the result of a whole-body scan. Data on the remaining 41 persons were used to control these models. Results: Bone mineral content, bone area, and bone mineral areal density (BMDA) of the lumbar spine were measured significantly lower by whole-body scans than by regional scans (p<0.0001). The difference was larger for the lower values of bone area and BMDA. We developed models that predicted lumbar spine BMDA from whole-body results. When these models were controlled in another group, the mean error between the methods was non-significant and the error was unrelated to the BMDA value. However, the variance of the error was only minimally reduced. Conclusions: Lumbar spine bone mineral was measured significantly lower by whole-body DXA than by regional DXA. Based on local data, models were developed that removed the significant difference between the methods.