Accounting for the Influence of Inflammation on Retinol Binding Protein in a Population Survey of Liberian Preschool‐Aged Children

Abstract

Vitamin A deficiency (VAD) is an important contributor to child morbidity and mortality. The prevalence of VAD, measured by retinol binding protein (RBP) and retinol, is overestimated in populations with a high prevalence of inflammation. We aimed to quantify and adjust for the effect of inflammation on VAD prevalence in a nationally representative survey of Liberian children 6 to 35 months of age.We compared four methods to adjust RBP for inflammation and estimate VAD prevalence: 1) ignoring inflammation, 2) excluding individuals with inflammation (elevated C‐reactive protein (CRP) or alpha1‐acid glycoprotein (AGP), 3) multiplying each individual's RBP by a correction factor, and 4) using regression (corrected RBP = RBP ‐ β1(CRPobs‐CRPref) ‐ β2(AGPobs‐AGPref). Corrected RBP was based on a regression model where CRP and AGP were set to the maximum of the lowest quintile.The unadjusted prevalence of VAD was 28%. Children with elevated CRP and/or AGP had significantly lower RBP concentrations (by 14%) than apparently healthy children. Using methods 2‐4 resulted in a prevalence of VAD of 20%, 18%, and 7%, respectively. Depending on the approach, ignoring inflammation would result in an overestimation of VAD prevalence of 28‐75%.Further quantification of the influence of inflammation on biomarkers of vitamin A status from national surveys is needed to compare and recommend the preferred adjustment method across populations.Support: BMGF, CDC, GAIN, NICHD