Investigating heterogeneity in studies of resting energy expenditure in persons with HIV/AIDS: a meta-analysis.

BACKGROUND: There is conflict in the literature about the extent of alterations of resting energy expenditure (REE) in persons with HIV. OBJECTIVE: The study was conducted to ascertain the mean difference in REE (in kJ) per kilogram of fat-free mass (FFM; REE/FFM) between HIV-positive subjects and control subjects and to investigate heterogeneity in the literature. DESIGN: A meta-analysis comparing classical and Bayesian methods was conducted. Heterogeneity was investigated by using subgroup analysis, metaregression, and a mixed indirect comparison. RESULTS: Of 58 studies meeting the inclusion criteria, 32 included both HIV-positive and control groups; 24 of these 32 were included. Thirty-seven studies were used in the mixed indirect comparison, and 30 were used in the subgroup comparisons of the HIV-symptomatic, lipodystrophy, weight-losing, and weight-stable subgroups and the healthy (HIV-negative) control group. Mean REE/FFM was significantly higher in 732 HIV-positive subjects than in 340 control subjects [11.93 kJ/kg (95% CI: 8.44,15.43 kJ/kg) and 12.47 kJ/kg (95% CI: 8.19,16.57 kJ/kg), classical and Bayesian random effects, respectively]; the test for heterogeneity was significant (P < 0.001). Both the mixed indirect comparison and the subgroup analysis indicated that REE/FFM was highest in the symptomatic subgroup; however, the small number of studies investigating symptomatic subjects limited statistical comparisons. The presence of lipodystrophy, use of highly active antiretroviral therapy, subject age, and method of body-composition measurement could not explain the heterogeneity in the data with the use of metaregression. CONCLUSIONS: REE/FFM (kJ/kg) is significantly higher in HIV-positive subjects than in healthy control subjects. Symptomatic HIV infection may contribute to the variations reported in the literature.