Dual-energy X-ray performs as well as clinical computed tomography for the measurement of visceral fat

Abstract

Visceral adipose tissue (VAT) is associated with adverse health effects including cardiovascular disease and type 2 diabetes. We developed a dual-energy X-ray absorptiometry (DXA) measurement of visceral adipose tissue (DXA-VAT) as a low cost and low radiation alternative to computed tomography (CT). DXA-VAT was compared to VAT assessed using CT by an expert reader (E-VAT). In addition, the same CT slice was also read by a clinical radiographer (C-VAT) and a best-fit anthropomorphic and demographic VAT model (A-VAT) was developed. Whole body DXA, CT at L4-L5, and anthropometry were measured on 272 black and white South African women (age 29 ± 8 years, BMI 28 ± 7 kg/m(2), waist circumference (WC) 89 ± 16 cm). Approximately one-half of the dataset (n = 141) was randomly selected and used as a training set for the development of DXA-VAT and A-VAT, which were then used to estimate VAT on the remaining 131 women in a blinded fashion. DXA-VAT (r = 0.93, standard error of the estimate (SEE) = 16 cm(2)) and C-VAT (r = 0.93, SEE = 16 cm(2)) were strongly correlated to E-VAT. These correlations with E-VAT were significantly stronger (P < 0.001) than the correlations of individual anthropometry measurements and the A-VAT model (WC + age, r = 0.79, SEE = 27 cm(2)). The inclusion of anthropometric and demographic measurements did not substantially improve the correlation between DXA-VAT and E-VAT. DXA-VAT performed as well as a clinical read of VAT from a CT scan and better than anthropomorphic and demographic models.

Figure 1

DXA-VAT region of measurement. The pure subcutaneous fat lateral to the abdominal muscles can be seen in the image. DXA-VAT, dual-energy X-ray absorptiometry-visceral adipose tissue.

Figure 2

Correlations between (a) E-VAT and DXA-VAT,(b) C-VAT, and (c) A-VAT. Only the validation set data are plotted for DXA-VAT and A-VAT, whereas the complete study set are plotted for C-VAT. A-VAT, anthropomorphic and demographic VAT model; C-VAT, clinical radiographer-VAT; DXA-VAT, dual-energy X-ray absorptiometry-visceral adipose tissue; E-VAT, expert reader-VAT; SEE, standard error of the estimate; VAT, visceral adipose tissue.

Figure 3

Bland–Altman plots and linear regression estimate, with 95% prediction bands, between (a) E-VAT and DXA-VAT, (b) C-VAT, and (c) A-VAT. A-VAT, anthropomorphic and demographic VAT model; C-VAT, clinical radiographer-VAT; DXA-VAT, dual-energy X-ray absorptiometry-visceral adipose tissue; E-VAT, expert reader-VAT; VAT, visceral adipose tissue.