Studies in persons without HIV infection have compared dual energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) measured adipose tissue (AT), but no such study has been conducted in HIV+ subjects, who have a high prevalence of regional fat loss.
We compared DXA with MRI-measured trunk, leg, arm, and total fat in HIV+ and control subjects.
Cross-sectional analysis in 877 HIV+ and 260 controls in FRAM (Fat Redistribution and Metabolic Change in HIV Infection), stratified by sex and HIV status.
Univariate associations of DXA with MRI were strongest for total and trunk fat (r≥0.92), and slightly weaker in leg (r≥0.87) and arm (r≥0.71). Estimated limb fat averaged substantially higher for DXA than MRI for HIV+ and control, men and women (all p<0.0001). Trunk showed much less difference between DXA and MRI, but was still statistically significant (p<0.0001). Bland-Altman plots showed increasing differences and variability; higher average limb fat in controls and HIV+ (both p<0.0001) was associated with greater DXA vs. MRI difference. As controls have more limb fat than HIV+, the bias leads to even higher fat measured by DXA than by MRI when controls are compared to HIV+; more HIV+ subjects had leg fat in the bottom decile of controls by DXA than by MRI (p<0.0001).
Although DXA and MRI-measured AT depots correlate strongly in HIV+ subjects and controls, differences increase as average fat increases, particularly for limb fat. DXA may estimate a higher peripheral lipoatrophy prevalence than MRI in HIV+ subjects.