Cross Calibration of Bone Mineral Density Values Among Three Dual Energy X-ray Absorptiometry Systems

Abstract

The generalized Least Significant Change (GLSC) is at a 95% confidence interval of precision error in the bone mineral density (BMD). The objectives of the research were to generate the GLSC values among three DXA machines (Lunar Model Prodigy, HOLOGIC Model Discovery A and Discovery W), to predict Bone mineral Density (BMD) values from cross calibration equations and to compare our predicted BMDs. Our research – derived with equation together with those from the manufacturers equations and observed BMDs from actual measurements. BMD measurements were performed on 30 females (age 20 - 80) at the lumbar spine and proximal femur. Each site was measured with all 3 DXA machines twice with repositioning in between. All measurement and analysis steps complied with the ISCD official position. The GLSCs were as follows: between Lunar Prodigy and Hologic Discovery A at the lumbar spine, the neck of femur and the total hip is at 0.066, 0.088, and 0.066 (g/cm²), respectively; between Lunar Prodigy and Hologic Discovery W at the lumbar spine, the neck of femur and the total hip is at 0.064, 0.076, and 0.070. (g/cm²), respectively; between Hologic Discovery A and Hologic Discovery W at the lumbar spine, the neck of femur and the total hip is at 0.020, 0.074, and 0.062 (g/cm²), respectively. The comparison of the errors from both equations found that the lumbar spine and total hip were statistically significant but not statistically significant at the neck of femur. These errors were larger than GLSCs therefore, the calculation of GLSCs by using the data collection was more appropriate for cross calibration of the BMDs than the calculated BMDs from both equations.