title: Investigating heterogeneity in studies of resting energy expenditure in persons with HIV/AIDS: a meta-analysis.
abstract: 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.
  
  
  METHODS
  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.
authors.affiliation: Smart Foods Centre, University of Wollongong, Australia. marijka@uow.edu.au
authors.forename: Marijka J
authors.initials: MJ
authors.lastname: Batterham
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000378:metabolism*; D000328:Adult; D000367:Age Factors; D023241:Antiretroviral Therapy, Highly Active / Q000009:adverse effects; D001481:Basal Metabolism / Q000502:physiology*; D001499:Bayes Theorem; D001823:Body Composition / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D015658:HIV Infections / Q000378:metabolism*; D039682:HIV-Associated Lipodystrophy Syndrome / Q000378:metabolism*; D006801:Humans; D008297:Male; D012044:Regression Analysis