title: The importance of controlling for the acute-phase response in the population-based assessment of vitamin A status: a study in children of pre-school age in Uganda.
abstract: OBJECTIVE
  To improve estimates of vitamin A deficiency in children of pre-school age in the 2006 Uganda Demographic and Health Survey (UDHS 2006).
  
  
  METHODS
  A cross-sectional study in which dried blood spot samples were analysed for C-reactive protein (CRP). Retinol-binding protein (RBP) had previously been analysed using a commercial enzyme immunoassay.
  
  
  METHODS
  A population-based study in Uganda.
  
  
  METHODS
  A systematically selected subset of the dried blood spot samples collected from children aged 6–59 months for UDHS 2006. Children were categorized into ‘normal CRP’ (Group A) and ‘raised CRP’ (Group B) using a CRP cut-off of 5mg/l. A correction factor was calculated to adjust the Group B RBP values for the influence of the acute-phase response.
  
  
  RESULTS
  Geometric mean CRP was 6.2 (95% CI 5.5, 7.0) mg/l, 1.6 (95% CI 1.5, 1.8) mg/l and 17.9 (95% CI 16.4, 19.6) mg/l in all children, in Group A and in Group B, respectively. Geometric mean RBP in all children, in Group A and in Group B was 1.18 (95% CI 1.14, 1.22)mmol/l, 1.26 (95% CI 1.20, 1.33)mmol/l and 1.12 (95% CI 1.07, 1.17)mmol/l, respectively, before correction. Correction increased mean RBP in Group B to 1.26 (95% CI 1.21, 1.31)mmol/l. The prevalence of vitamin A deficiency (RBP,0.825mmol/l) reduced from 18.4% (95% CI 17.2, 23.0%) to 13.9% (95% CI 11.3, 16.5%).
  
  
  CONCLUSIONS
  Correcting for the acute-phase response significantly reduced the prevalence of vitamin A deficiency; thus, the acute-phase response should be considered when vitamin A status is assessed using RBP in order to improve population-level estimates of vitamin A deficiency.
authors.affiliation: Department of Biochemistry, Makerere University, PO Box 7062, Kampala, Uganda. rbaingana@sci.mak.ac.ug
authors.forename: Rhona
authors.initials: R
authors.lastname: Baingana
authors.forename: Dennis
authors.initials: D
authors.lastname: Matovu-Kasozi
authors.forename: Dean
authors.initials: D
authors.lastname: Garrett
mesh_terms: D000210:Acute-Phase Reaction / Q000097:blood*; D002097:C-Reactive Protein / Q000378:metabolism*; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D006306:Health Surveys; D006801:Humans; D007223:Infant; D015596:Nutrition Assessment; D009752:Nutritional Status; D012016:Reference Values; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D014454:Uganda / Q000453:epidemiology; D014801:Vitamin A / Q000097:blood*; D014802:Vitamin A Deficiency / Q000097:blood* / Q000453:epidemiology
chemical_list: D012177:Retinol-Binding Proteins; D014801:Vitamin A; D002097:C-Reactive Protein