title: Use of serum retinol-binding protein for prediction of vitamin A deficiency: effects of HIV-1 infection, protein malnutrition, and the acute phase response.
abstract: BACKGROUND
  Serum retinol is the most commonly used indicator of vitamin A status. Retinol is transported in a 1-to-1 complex with retinol-binding protein (RBP). RBP is easy and inexpensive to measure, and studies have shown a high correlation between concentrations of RBP and concentrations of retinol. The performance of RBP in the context of infection or protein malnutrition, however, has not been evaluated.
  
  
  OBJECTIVE
  Our aim was to determine whether RBP is a good surrogate measure for retinol in the context of HIV-1 infection, protein malnutrition, and the acute phase response.
  
  
  METHODS
  The relation between RBP and retinol was examined in a cross-sectional study of 600 Kenyan women.
  
  
  RESULTS
  There was a high correlation between concentrations of RBP and those of retinol (r = 0.88). When equimolar cutoffs were used, RBP predicted marginal vitamin A status (retinol < 1.05 micro mol/L) with 93% sensitivity and 75% specificity and vitamin A deficiency (retinol < 0.70 micro mol/L) with 91% sensitivity and 94% specificity. Similarly high sensitivities and specificities were found among subgroups with HIV-1 infection, a positive acute phase response, and protein malnutrition. Protein malnutrition and a positive acute phase response were common, especially among HIV-1-infected women, and were independently and synergistically associated with lower RBP concentrations.
  
  
  CONCLUSIONS
  Equimolar RBP cutoffs predict vitamin A deficiency with high sensitivity and specificity, even in the context of infection and protein malnutrition. Like retinol, RBP may not accurately identify true vitamin A status under all conditions, because the acute phase response and protein malnutrition depress RBP concentrations. However, RBP may be a simple, inexpensive tool for assessment of vitamin A deficiency in population studies.
authors.affiliation: Department of Epidemiology, University of Washington, Seattle, WA 98104, USA. jbaeten@u.washington.edu
authors.forename: Jared M
authors.initials: JM
authors.lastname: Baeten
authors.forename: Barbra A
authors.initials: BA
authors.lastname: Richardson
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Bankson
authors.forename: Mark H
authors.initials: MH
authors.lastname: Wener
authors.forename: Joan K
authors.initials: JK
authors.lastname: Kreiss
authors.forename: Ludo
authors.initials: L
authors.lastname: Lavreys
authors.forename: Kishorchandra
authors.initials: K
authors.lastname: Mandaliya
authors.forename: Job J
authors.initials: JJ
authors.lastname: Bwayo
authors.forename: R Scott
authors.initials: RS
authors.lastname: McClelland
mesh_terms: D000210:Acute-Phase Reaction / Q000209:etiology*; D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000097:blood* / Q000150:complications; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D009752:Nutritional Status; D011502:Protein-Energy Malnutrition / Q000097:blood* / Q000150:complications; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D014801:Vitamin A / Q000097:blood*; D014802:Vitamin A Deficiency / Q000097:blood* / Q000453:epidemiology / Q000209:etiology
chemical_list: D012177:Retinol-Binding Proteins; D014801:Vitamin A