Accuracy of Longitudinal Assessment of Visceral Adipose Tissue by Dual-Energy X-Ray Absorptiometry in Children with Obesity

Abstract

Background: Increased visceral adipose tissue (VAT) is strongly associated with cardiometabolic risk factors. Accurate quantification of VAT is available through magnetic resonance imaging (MRI), which incurs a significant financial and time burden. We aimed to assess the accuracy of dual-energy X-ray absorptiometry- (DXA-) derived VAT (DXA-VAT) against a gold standard MRI protocol (MRI-VAT) in children with normal weight and obesity cross-sectionally, and over the course of a lifestyle intervention.

Methodology: MRI-VAT and DXA-VAT were quantified in 61 children (30 normal weight and 31 with obesity) at baseline. Children with obesity entered a three-month exercise and/or nutrition intervention after which VAT was reassessed. MRI- and DXA-VAT cross-sectional area, volume, and mass were quantified, and associations were calculated at baseline (n = 61) and pre-post intervention (n = 28, 3 participants dropped out). Method agreement was assessed through Bland-Altman analysis, linear regression, and Passing-Bablok regression.

Results: At baseline, all DXA- and MRI-VAT outcomes were strongly associated (r = 0.90, P < 0.001). However, there were no significant associations between absolute or relative change in DXA- and MRI-VAT outcomes (r = 0.25-0.36, P > 0.05). DXA significantly overestimated VAT CSA (cross-sectional area), volume, and mass when compared with MRI (P < 0.001) at baseline. Significant proportional bias was observed for all DXA-VAT outcomes at baseline and for relative longitudinal changes in DXA-VAT.

Conclusions: Although DXA-VAT outcomes were strongly associated with MRI-VAT outcomes at baseline, estimates were subject to proportional bias in children with obesity and normal weight. DXA lacks validity for detecting changes in VAT among children with obesity. This trial is registered with NCT01991106.

Conflict of interest statement

Dr. Coombes reports grants from Coca-Cola and Renew Corp and personal fees from Tolmar Pharmaceuticals and Novo Nordisk Pharmaceuticals, all outside the submitted work. Dr. Keating reports grants from Exercise and Sports Science Australia and Diabetes Australia, all outside the submitted work. The remaining authors have no conflicts of interest relevant to this article to disclose.

Copyright © 2019 Katrin A. Dias et al.

Figures

Figure 1

Subcutaneous (red) and visceral (green) adipose tissue compartments shown on DXA (a) and MRI (b). Blue dashed lines on DXA panel show the abdominal wall musculature.

Figure 2

Linear regression illustrating the relationship between MRI- and DXA-VAT CSA (a), volume (b), and mass (c) in all participants. Dashed lines represent 95% confidence intervals.

Figure 3

Bland–Altman plots comparing MRI-VAT (reference) with DXA-VAT CSA (a), volume (b), and mass (c) in all participants. The plots show the mean difference between the two measures (thick solid line), the upper and lower limits of agreement (thin solid line), 95% confidence intervals (dashed lines), line of equality (y = 0, dotted line), and the regression line of differences (dashed-dotted line). MD = mean difference; LoA = limits of agreement.

Figure 4

Passing–Bablok regression plots comparing MRI-VAT (reference) with DXA-VAT CSA (a), volume (b), and mass (c) in all participants. The plots show the regression line (solid line), 95% confidence intervals (dashed lines), and identity line (x = y dotted line).

Figure 5

Linear regression illustrating the relationship between absolute and relative change in MRI- and change DXA-CSA (a, b), volume (c, d), and mass (e, f). Dotted lines represent 95% confidence intervals.

Figure 6

Bland–Altman plots comparing absolute and relative change in MRI-VAT (reference) with absolute and relative change in DXA-VAT CSA (a, b), volume (c, d), and mass (e, f). The plots show the mean difference between the two measures (thick solid line), the upper and lower limits of agreement (thin solid line), 95% confidence intervals (dashed lines), line of equality (y = 0, dotted line), and the regression line of differences (dashed dotted line). MD = mean difference; LoA = limits of agreement.