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1.  Comparison of DXA and MRI-measured adipose tissue depots in HIV-infected and control subjects 
Background
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.
Objective
We compared DXA with MRI-measured trunk, leg, arm, and total fat in HIV+ and control subjects.
Design
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.
Results
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).
Conclusions
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.
PMCID: PMC3156610  PMID: 18842798
DXA; MRI; adipose tissue depots; lipoatrophy; HIV infection
2.  Simple anthropometric measures correlate with metabolic risk indicators as strongly as magnetic resonance imaging–measured adipose tissue depots in both HIV-infected and control subjects2 
Background
Studies in persons without HIV infection have compared percentage body fat (%BF) and waist circumference as markers of risk for the complications of excess adiposity, but only limited study has been conducted in HIV-infected subjects.
Objective
We compared anthropometric and magnetic resonance imaging (MRI)–based adiposity measures as correlates of metabolic complications of adiposity in HIV-infected and control subjects.
Design
The study was a cross-sectional analysis of 666 HIV-positive and 242 control subjects in the Fat Redistribution and Metabolic Change in HIV Infection (FRAM) study assessing body mass index (BMI), waist (WC) and hip (HC) circumferences, waist-to-hip ratio (WHR), %BF, and MRI-measured regional adipose tissue. Study outcomes were 3 metabolic risk variables [homeostatic model assessment (HOMA), triglycerides, and HDL cholesterol]. Analyses were stratified by sex and HIV status and adjusted for demographic, lifestyle, and HIV-related factors.
Results
In HIV-infected and control subjects, univariate associations with HOMA, triglycerides, and HDL were strongest for WC, MRI-measured visceral adipose tissue, and WHR; in all cases, differences in correlation between the strongest measures for each outcome were small (r ≤ 0.07). Multivariate adjustment found no significant difference for optimally fitting models between the use of anthropometric and MRI measures, and the magnitudes of differences were small (adjusted R2 ≤ 0.06). For HOMA and HDL, WC appeared to be the best anthropometric correlate of metabolic complications, whereas, for triglycerides, the best was WHR.
Conclusion
Relations of simple anthropometric measures with HOMA, triglycerides, and HDL cholesterol are approximately as strong as MRI-measured whole-body adipose tissue depots in both HIV-infected and control subjects.
PMCID: PMC2587301  PMID: 18541572

Results 1-2 (2)