Cross-Calibration of iDXA and Prodigy on Spine and Femur Scans in Korean Adults

In this study, the authors compared bone mineral density (BMD) determined using GE Lunar iDXA and Prodigy and derived cross-calibration equations for the 2 devices in Korean adults. One hundred subjects (66 women and 34 men) participated in this study. Bone mineral density of spine and femur was measured by iDXA and Prodigy dual-energy X-ray absorptiometry (GE Lunar, Madison, WI). Subjects were divided into 3 groups. The first group (30 subjects) was scanned twice using Prodigy for precision testing and then once using iDXA. The second group (30 subjects) was scanned twice using iDXA and then once using Prodigy. Cross-calibration equations were derived using these results. The derived equations were tested in the third group (40 subjects). Predicted values from calculations based on Prodigy findings were compared with measured iDXA data. A significant difference was found between the BMD determined using the 2 devices (p < 0.001). However, linear regression analysis showed a high level of agreement between the two (r2 from 0.984 to 0.994, p < 0.001). Bland-Altman analysis revealed no significant correlations between Prodigy and iDXA. Cross-calibration equations decreased systematic errors between Prodigy and iDXA by 0.4% at the spine, 0.8% at the femoral neck, and 0.1% at the total femur. A high level of agreement was found between Prodigy and iDXA in Korean adults. Cross-calibration equations proved reliable based on comparisons of measured and calculated BMD values.