title: Accounting for the influence of inflammation on retinol-binding protein in a population survey of Liberian preschool-age 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) or 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 five approaches to adjust RBP for inflammation and estimate VAD prevalence (defined as RBP < 0.7 µmol/L): (1) ignoring inflammation; (2) excluding individuals with inflammation (C-reactive protein (CRP) >5 mg/L or alpha1-acid glycoprotein (AGP) >1 g/)L; (3) multiplying each individual's RBP by an internal correction factor; (4) by an external correction factor; and (5) using regression (corrected RBP = exp(InRBP - β1(lnCRPobs-lnCRPref) - β2(lnAGPobs-lnAGPref)). Corrected RBP was based on a regression model where reference lnCRP and lnAGP were set to the maximum of the lowest decile. The unadjusted prevalence of VAD was 24.7%. Children with elevated CRP and/or AGP had significantly lower RBP concentrations than their apparently healthy peers (geometric mean RBP 0.79 µmol/L (95% CI: 0.76, 0.82) vs. 0.95 µmol/L (95% CI: 0.92, 0.97), P < 0.001). Using approaches 2-5 resulted in a prevalence of VAD of 11.6%, 14.3%, 13.5% and 7.3%, respectively. Depending on the approach, the VAD prevalence is reduced 10-17 percentage points when inflammation is taken into account. Further quantification of the influence of inflammation on biomarkers of vitamin A status from other national surveys is needed to compare and recommend the preferred adjustment approach across populations.
authors: Nutrition and Health Sciences Program, Laney Graduate School, Emory University, Atlanta, Georgia, USA.
authors: Leila Margaret
authors: LM
authors: Larson
authors: Rollins School of Public Health, Emory University, Atlanta, Georgia, USA.
authors: O Yaw
authors: OY
authors: Addo
authors: UNICEF Regional Office for West and Central Africa, Dakar, Senegal.
authors: Fanny
authors: F
authors: Sandalinas
authors: UNICEF Liberia, Monrovia, Liberia.
authors: Katherine
authors: K
authors: Faigao
authors: UNICEF Regional Office for West and Central Africa, Dakar, Senegal.
authors: Roland
authors: R
authors: Kupka
authors: Rollins School of Public Health, Emory University, Atlanta, Georgia, USA.|Nutrition Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors: Rafael
authors: R
authors: Flores-Ayala
authors: Nutrition and Health Sciences Program, Laney Graduate School, Emory University, Atlanta, Georgia, USA.|Rollins School of Public Health, Emory University, Atlanta, Georgia, USA.|Nutrition Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors: Parminder S
authors: PS
authors: Suchdev
mesh_terms: D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007223:Infant; D007249:Inflammation / Q000453:epidemiology*; D007988:Liberia / Q000453:epidemiology; D009017:Morbidity; D009752:Nutritional Status; D009961:Orosomucoid / Q000378:metabolism; D015995:Prevalence; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D014801:Vitamin A / Q000097:blood; D014802:Vitamin A Deficiency / Q000097:blood / Q000453:epidemiology*
chemical_list: D015415:Biomarkers; D006454:Hemoglobins; D009961:Orosomucoid; D012177:Retinol-Binding Proteins; D014801:Vitamin A; D002097:C-Reactive Protein
keywords: C-reactive protein; alpha1-acid glycoprotein; inflammation; nutrition; retinol-binding protein; vitamin A deficiency