DISCRIMINATORY ABILITY OF BONE MASS MEASUREMENTS (SPA AND DEXA) FOR FRACTURES IN ELDERLY POSTMENOPAUSAL WOMEN

We investigated the discriminatory ability of forearm bone mineral content (BMC(arm)) measured by single photon absorptiometry (SPA) and spinal bone mineral density (BMD(spine)) measured by dual-energy X-ray absorptiometry (DEXA) in 387 elderly postmenopausal women. Of these, 22 had never sustained a fracture (normal), 91 had had less than three vertebral wedge fractures (mild), 51 had experienced a peripheral fracture (moderate), and 24 had had more than three vertebral wedge or compression fractures (severe). BMC(arm) exceeded BMD(spine) slightly in the ability to discriminate the mild and moderate groups (P < 0.01-0.001), whether calculations were performed on raw values or the Z-scores compared with premenopausal women. Receiver operating (ROC) analysis showed that at every cutoff level BMC(arm) had a similar ability as BMD(spine) to discriminate between the vertebral fracture (mild and severe) groups and healthy premenopausal and nonfractured postmenopausal women (normal), whereas BMC(arm) had a significantly higher discriminatory ability of peripheral fractures (P < 0.05) (moderate) group compared with premenopausal women. We conclude that SPA and DEXA are equally capable as diagnostic procedures in women with established osteoporosis.