Comparison of single-slice CT and DXA-derived measures of central adiposity in South African women.

Background: Visceral adipose tissue (VAT) accumulation is a known risk factor for cardiometabolic diseases. Efficient imaging modalities are necessary to quantify VAT. The study assessed the agreement between dual-energy x-ray absorptiometry (DXA) and single-slice computed tomography (CT) for abdominal fat quantification in mixed-ancestry South African women, and determined if this differed by body mass index (BMI) categories.

Methods: VAT and abdominal subcutaneous adipose tissue (SAT) were measured using single-slice CT and DXA in 132 women aged 55 (45-64) years. Participants were categorised as normal weight (BMI < 25 kg/m2), overweight (BMI: 25-29.9 kg/m2) and obese (BMI ≥ 30 kg/m2). Pearson correlation coefficients and Bland-Altman analysis were used to determine agreement between the two measurements.

Results: Two thirds of the participants were obese. DXA and CT-derived measurements of abdominal VAT and SAT were significantly correlated in the overall sample (r = 0.872 and r = 0.966, both p < 0.001, respectively) and within BMI categories. DXA overestimated VAT and SAT in the overall sample and across BMI categories. In the overall sample, the mean difference (DXA-CT estimates) was 75.3 cm2 (95% CI: 68.8-81.8 cm2, p ≤ 0.0001) for VAT and 54.7 cm2 (47.1-62.3 cm2, p ≤ 0.0001) for SAT. Within increasing BMI categories, the variance between the two modalities was fixed for VAT (p = 0.359 for obese), whereas the variance for SAT was heteroscedastic (p ≤ 0.0001).

Conclusions: DXA overestimated VAT and abdominal SAT in a sample of middle-aged mixed-ancestry South African women. VAT variance was fixed in the obesity category, an indication that DXA may be valid in measuring VAT in obese people.