Dual-energy X-ray Performs as Well as Clinical Computer Tomography for the Measurement of Visceral Fat

Introduction:  Adverse health effects, such as cardiovascular disease and type 2 diabetes, are associated with visceral adipose tissue (VAT); VAT is thought to be more closely associated with obesity-related metabolic diseases than other obesity indexes, including BMI, waist circumference (WC), and waist-to-height ratio (WhtR).

To measure VAT, the gold standards are computed tomography (CT) and magnetic resonance imaging (MRI), but there are barriers to their use:

Therefore, dual-energy x-ray absorptiometry (DXA) is a possibility for measuring VAT with lower radiation exposure and cost.  This study was done to further refine DXA measurement of VAT (DXA-VAT).

Methods:  There were 272 women in this study that was done in South Africa.  Their age range was 18-49 years, and their BMI range was 17.7-45.8 kg/m2.  Whole body DXA, CT at L4-L5, and anthropomorphic analysis were done on all subjects. 

The training set were 141 randomly selected women from this dataset.  Their DXA-VAT was compared to CT-assessed VAT by an expert reader (E-VAT).  That same CT sample was read by a clinical radiographer (C-VAT); from that, a best-fit anthropomorphic and demographic VAT model (A-VAT) was created.
The DXA-VAT and the A-VAT were then applied to the remaining 131 women for validation in order to estimate their VAT.

Results:  DXA-VAT and C-VAT were strongly correlated with E-VAT, and those correlations were significantly stronger (p < 0.001) than the correlations of A-VAT and individual anthropometry measurements (WC + age, r = 0.79).

Including the anthropometric and demographic measurements did not improve the DXA-VAT and E-VAT correlations.

Conclusions:  A strong linear relationship existed between DXA-VAT and E-VAT, suggesting that DXA-VAT may be a reliable alternative to CT or MRI for estimating VAT.  Further study is needed in other populations.

Commentary by J. Michael Gonzalez-Campoy MD, PhD, FACE

For clinical pearls from this study, read Dr. Gonzalez-Campoy's introduction to this issue of EndoScan.