Introduction: Visceral adipose tissue (VAT) is a strong predictor of cardiometabolic risk. Magnetic resonance imaging (MRI) is recognised as a valid approach to assess VAT, however cost limits use in clinical settings. Instead, waist circumference (WC) is commonly used as a surrogate measure to assess VAT. Dual energy x-ray absorptiometry (DXA) can now estimate VAT, however its reliability and validity to measure change in VAT over time remains unclear. The aim of this study was to compare the measurement of VAT volume from DXA to MRI.
Methods: 29 participants (26 male) with coronary artery disease (64±8 years BMI 27.8±3.5 kg/m2) were measured at baseline and following a 12-week exercise program. VAT and abdominal subcutaneous fat (SAT) were measured by a 3 Telsa MRI system. Transverse slice images from diaphragm to pelvis (L5/S1) were used to quantify total volumes by semi-automated specialised software. To measure the reliability of DXA to estimate VAT, two DXA scans were performed at baseline and analysed using intra-class correlation. Validity was assessed by Bland Altman analysis.
Results: The reliability of DXA for VAT estimation was excellent with intra-class correlation of 0.997. There was a strong linear correlation between DXA and MRI for VAT volume at baseline (r=0.89; p<0.001, and change over time (r=0.72; p<0.001). However Bland Altman analysis revealed significant underestimation of VAT volume by DXA at baseline (-749cm3 [-1633cm3–135cm3], p<0.001), and change over time (-176cm3 [-555cm3–203cm3], p<0.001). WC had a strong correlation with VAT volume at baseline (r=0.80; p<0.001) but association to longitudinal change in VAT volume was not as strong (r=0.43; p=0.020). Instead, change in SAT showed a strong correlation with change in WC (r=0.81; p<0.001).
Conclusion: DXA significantly underestimates cross-sectional and longitudinal change in VAT volume compared to MRI. However DXA is more predictive of change in VAT than WC.