How reliable is the ultrasound densitometer for community screening to diagnose osteoporosis in spine, femur, and forearm?

Dual X-ray absorptiometry (DXA) is the most widely used noninvasive, quantitative diagnostic method of measuring bone density, but it exhibits several limitations for the purpose of general screening and community-based study. Thus, we evaluated the feasibility of the ultrasound densitometer SoundScan Compact for screening the osteoporosis community. We compared the reliability of the SoundScan Compact's measurement to predict both osteopenia and osteoporosis at the spine, femur, and forearm measured by the XR-36. World Health Organisation criteria and Korean reference were used for the diagnosis of osteopenia and osteoporosis. Of the 1827 subjects screened in the community, we randomly selected and invited 106 subjects to our university hospital center for clinical epidemiology for further evaluation of their bone health using DXA. The site-specific relationships among speed of sound and bone mineral density at L2-L4 spine, femoral neck, trochanter, Ward's triangle, distal radius + ulna, proximal radius + ulna, and proximal radius were highly correlated with r values of 0.633, 0.632, 0.674, 0.632, 0.668, 0.78, and 0.777 respectively (all p < 0.0001). Of the 42 subjects defined as normal in the spine by SoundScan Compact's, 27 (64.3%) were also in agreement as the normal by the XR-36. However, an agreement of 43.5% (10/23) in osteopenia and 53.7% (22/41) in osteoporosis was less sensitive. Reliability tested by kappa statistics (kappa = 0.35; t = 5.3; p < 0.0001) revealed that the degree of agreement was not coincidental. On the femur, 54.8% (23/42) agreed as normal, 73.9% (17/23) as osteopenia, and 39% (16/41) as osteoporosis (kappa = 0.33; t = 5.5; p < 0.0001). Higher reliability was found in the forearm, with a kappa value of 0.48, t = 7.2, and p < 0.0001. A magnitude of agreement was also greater in the forearm, with 83.3% (35/42) agreement in normal, 52.2% (12/23) in osteopenia, and 64% (16/25) in osteoporosis. Although the SoundScan Compact's measures different bone properties and measurements are taken at different sites, it is a very useful instrument with a high correlation and high degree of variation and reliability to predict bone health at other sites such as the spine, femur, and forearm. The ultrasound densitometer such as SoundScan Compact's merits its use for community screening and in the primary care setting to detect osteopenia and osteoporosis for the purpose of early detection and prevention.