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 MRI from the same defined abdominal region. METHODS: Participants (N=93 (50m, 43f), BMI: 19.1–57.6 kg/m(2)) underwent dual-energy X-ray absorptiometry (DXA) scans on two DXA systems (iDXA and Lunar Prodigy), and a subgroup underwent abdominal MRI imaging for quantification of VAT. RESULTS: Pfat correlated strongly between both machines (r(2)=0.98, P<1.0E-14). Bland-Altman plots showed a bias with higher measured pfat on iDXA versus Lunar Prodigy in leaner subjects and the opposite in more overweight subjects. The R(2), for regression of MRI on iDXA VAT-values was 0.948. Bland-Altman bias was +104.1 cm(3) with 95% limits of agreement of −681.9 to 890.0 cm(3). For both DXA methods, and iDXA v MRI determined VAT, comparison using rank regression demonstrated no order bias. CONCLUSIONS: The total pfat measured by both machines were 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 v 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.