Osteoporosis assessment by whole body region vs. site-specific DXA.

The ability of regional data from whole body scans to provide an accurate assessment of site-specific BMD, osteoporosis prevalence and fracture risk has not been fully explored. To address these issues, we measured total body (TBBD) and site-specific BMD in an age-stratified population sample of 351 women (21-93 years) and 348 men (22-90 years). We found an excellent correlation between AP lumbar spine and total body lumbar spine subregion BMD (r2=0.92), but weaker ones for total hip compared to pelvis region (r2=0.72) or between total wrist and left arm subregion from the whole body scan (r2=0.83). The error in estimating site-specific BMD from total body regions ranged from 4.3% (lumbar spine) to 11.2% (femoral neck) in women and from 4.9 to 11.1%, respectively, in men. Site-specific versus regional measurements at the lumbar spine and total hip/pelvis provided comparable overall estimates of osteoporosis prevalence, but disagreed on the status of individuals; measurements at whole body regions underestimated osteoporosis as assessed at the femoral neck or total wrist. All measurements were associated with a history of various fractures [age adjusted odds ratios (OR), 1.3 to 2.1 in women and 1.2 to 1.5 in men] and were generally interchangeable, but femoral neck BMD provided the best estimate of osteoporotic fracture risk in women (OR, 2.9; 95% CI, 1.7-5.0). Although there are strong correlations between BMD from dedicated scans of the hip, spine and distal forearm and corresponding regions on the whole body scan, the measurements provide somewhat different estimates of osteoporosis prevalence and fracture risk.