Use of serum retinol-binding protein for prediction of vitamin A deficiency: effects of HIV-1 infection, protein malnutrition, and the acute phase response
Baeten, J.M.; Richardson, B.A.; Bankson, D.D.; Wener, M.H.; Kreiss, J.K.; Lavreys, L.; Mandaliya, K.; Bwayo, J.J.; McClelland, R.Scott.
American Journal of Clinical Nutrition 79(2): 218-225
2004
ISSN/ISBN: 0002-9165 PMID: 14749226 DOI: 10.1093/ajcn/79.2.218Document Number: 232640
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. Design: 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 mmol/L) with 93% sensitivity and 75% specificity and vitamin A deficiency (retinol < 0.70 mmol/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. Reprinted by permission of the publisher.