Cross calibration of two dual-energy X-ray densitometers and comparison of visceral adipose tissue measurements by iDXA and MRI.

OBJECTIVE: Compare total percentage body fat (pfat) measurements between two densitometers and visceral adipose tissue (VAT) estimates between iDXA and magnetic resonance imaging (MRI) from the same defined abdominal region.

METHODS: Participants [N = 93 (50 men, 43 women), BMI: 19.1-57.6 kg/m2 ] underwent dual-energy X-ray absorptiometry (DXA) scans on two DXA systems (GE Healthcare Lunar iDXA and Lunar Prodigy), and a subgroup underwent abdominal MRI imaging for quantification of VAT.

RESULTS: Pfat correlated strongly between both machines (r2  = 0.98, P < 1.0E-14). Bland-Altman plots showed a bias with higher measured pfat on iDXA versus Prodigy in leaner subjects and the opposite in more overweight subjects. The R2 for regression of MRI on iDXA VAT values was 0.948. Bland-Altman bias was +104.1 cm3 with 95% limits of agreement of -681.9 to 890.0 cm3 . For both DXA methods, and iDXA versus MRI determined VAT, comparison using rank regression demonstrated no order bias.

CONCLUSIONS: The total pfat measured by both machines was strongly and linearly associated, allowing for conversion (equations are provided) of iDXA for assessment of longitudinal body fat changes. Despite a bias of abdominal VAT measures of iDXA versus MRI, the high rank correlation makes iDXA a good alternative to the more complicated and time-consuming MRI for use in larger cross-sectional and longitudinal studies.