Ability of peripheral DXA measurement to diagnose osteoporosis as assessed by central DXA measurement

In order to evaluate the utility of peripheral measurement of bone mineral density (BMD) in the diagnosis of osteoporosis, we measured BMD at the spine and femoral neck with central dual-energy X-ray absorptiometry (DXA), at phalanx with AccuDXA (Schick) as well as proximal and distal forearm with pDXA (Norland) in 835 women ranging in age from 20 to 85 yr. In receiver operating characteristic (ROC) curves, where a positive case was defined as a T-score <= -2.5 either on spine or femoral neck, the areas under the curve were not significantly different between sites. At a T-score of -2.5 as determined by each peripheral apparatus, sensitivity and specificity were, respectively, 0.39 and 0.95 for phalanx and 0.75 and 0.85 for proximal forearm whereas they were 0.42 and 0.96 for distal forearm. Using optimal absolute BMD cutoff values improved the results. Sensitivity and specificity were, respectively, 0.79 and 0.83 for phalanx at an absolute BMD value of 0.436 and 0.84 and 0.79 for proximal forearm at a value of 0.703, whereas they were 0.90 and 0.75 for distal forearm at a value of 0.208. Combining the two forearm measurements improves the results slightly. At cutoff values of 0.641 and 0.252, respectively for proximal and distal forearms, sensitivity was 0.83 and specificity was 0.84. Therefore, a peripheral measurement of BMD together with a good clinical evaluation of the osteoporosis risk profile of the patient, can be an interesting tool for the diagnosis of osteoporosis in areas where central DXA is not available.