Cross-Calibration of GE Healthcare Lunar Prodigy and iDXA Dual-Energy X-Ray Densitometers for Bone Mineral Measurements

Table 3

Mean (SD) values and linear correlation coefficients () of the in vivo dual-energy X-ray absorptiometry (DXA) measurements with Prodigy and iDXA (). Bland and Altman analysis results with relative mean differences % as well as limits of agreement [  ±  (1.96 × SD)]. Simple linear regression analysis of Prodigy (dependent) versus iDXA (independent) BMD data with standard error (SE) and standard errors of estimates (SEE). Systematic BMD differences were observed between Prodigy and iDXA. After linear regression correction equations were applied the differences were negligible.

BMD ROI	Prodigy; mean (SD)	iDXA; mean (SD)		%	Intercept (SE)	Slope (SE)	SEE	SEE (%)	Limits of agreement
Spine L2–L4	1.169 (0.145)	1.186 (0.149)	0.990	1.5		0.985 (0.002)	0.021	1.8	−0.025 to 0.059
Femoral neck	0.941 (0.129)	0.946 (0.128)	0.986	0.5		0.995 (0.003)	0.022	2.3	−0.037 to 0.048
Ward’s triangle	0.761 (0.145)	0.758 (0.148)	0.985	−0.4		1.002 (0.004)	0.026	3.4	−0.05 to 0.05
Trochanter	0.800 (0.102)	0.806 (0.108)	0.987	0.7	0.044 (0.015)	0.939 (0.019)	0.017	2.1	−0.030 to 0.040
Shaft	1.162 (0.164)	1.180 (0.168)	0.993	1.5		0.985 (0.002)	0.020	1.7	−0.022 to 0.058
Total hip	0.993 (0.126)	1.002 (0.129)	0.995	0.9		0.990 (0.002)	0.013	1.3	−0.016 to 0.034

Formula for relative mean difference (%): [(iDXA − Prodigy) × 100/Prodigy].
Significantly different () mean difference ( = Prodigy − iDXA, paired -test or nonparametric Wilcoxon signed-rank test in Ward’ triangle BMD, BMC, or area ROIs).
Correction equation: Prodigy (BMD) = Slope × iDXA (BMD) + intercept.
Formula for SEE (%): [SEE × 100/((Prodigy + iDXA)/2)].