DXA Estimated VAT Change after Surgery Induced Weight Loss in Women is Inaccurate

• Published in: Obesity (Silver Spring, Md.) Md.), 2021-12, Vol.29, p.84-85
• Main Authors: Ashby-Thompson, Maxine, Heshka, Stanley, Rizkalla, Bridgette, Tampa, Rosalie Zurlo, Lemos, Thaisa, Janumala, Isaiah, Goodpaster, Bret, Delany, James, Courcoulas, Anita, Strain, Gladys, Pomp, Alfons, Kang, Patrick, Lin, Susan, Thornton, John, Gallagher, Dympna
• Format: Article
• Language: English
• Subjects: Gastrointestinal surgery; Weight control
• ISSN: 1930-7381; 1930-739X

Background: Elevated VAT is an established metabolic risk factor. Reliable and simple methods to quantify changes in VAT are needed. The CoreScan™ (GE) software estimates VAT from a specified region on a whole-body DXA scan and has not been validated in persons with severe obesity or longitudinally after rapid weight loss. This study investigated the agreement between VAT by DXA and the criterion MRI method. Methods: Women with obesity (N = 36; age 43 years; 61% had BMI > 40kg/m2; 89% Caucasian) with iDXA and MRI scans before RYGB bariatric surgery (T0), and at (T12) 12- and (T24) 24-months post-surgery were analyzed. CoreScan™ VAT (DXA VAT) per manufacturer is the area between the top of the iliac crest and 20% of the distance from top of the iliac crest to the base of the skull. VAT by MRI, which reflected total VAT, was measured from VAT visible in slices extending from the base of the lungs to the tip of the sacrum/coccyx on a whole-body multislice MRI scan. Longitudinal analyses with time as a repeated measure, DXA VAT as a time-varying predictor and the interaction of time and DXA VAT were used to test whether the relation of DXA VAT to MRI VAT differed over time. Results: Mean DXA VAT was 45% of total VAT measured by MRI at T0, 47% at T12 and 68% at T24. At each time point, DXA and MRI VAT were strongly associated (R2 65-80%). However, significant amounts of change in MRI VAT between T0 and T12 were not accounted for by DXA changes (0.81 kg, p = 0.03) and the relation of DXA VAT to MRI VAT differed significantly between T12 and T24 (interaction p = 0.03). Conclusions: DXA VAT as measured by CoreScan™, within the limits of error, may be useful as an indicator of whether VAT has increased or decreased within the same subject. However, CoreScan™ lacks accuracy for comparing VAT across subjects or for estimating the size of changes within subject.