Plasma Retinol-Binding Protein Predicts Plasma Retinol Concentration in Both Infected and Uninfected Cameroonian Women and Children

Abstract

Variation in the relationship between plasma retinol-binding protein (RBP) and retinol (ROH) has implications for vitamin A (VA) status assessment using RBP. Our objectives were to identify factors affecting the RBP:ROH relationship and to derive and evaluate population-specific RBP cutoffs for VA deficiency (VAD) in Cameroon. Plasma RBP, C-reactive protein (CRP), α1-acid-glycoprotein (AGP), and ROH concentrations were compared in a subsample of women 15-49 y (n = 121) and children 12-59 mo (n = 123) included in a national survey conducted in 2009. Plasma RBP and ROH were highly correlated (r = 0.94 for women; r = 0.96 for children; P < 0.001). Pregnancy and lactation altered the RBP:ROH relationship in women, but obesity, elevated CRP and AGP, age, and VA status did not. Among children, age altered the RBP:ROH relationship, but sex, stunting, VA status, and elevated CRP and AGP did not. Cutoffs for VAD derived using regression analysis were <1.17 μmol RBP/L for women (corresponding to <1.05 μmol ROH/L) and <0.83 μmol RBP/L for children (corresponding to <0.70 μmol ROH/L). The sensitivity and specificity of derived cutoffs were 81.8 and 93.0% for women and 94.7 and 88.9% for children, respectively. The infection-adjusted prevalence of low VA status (<1.17 μmol RBP/L) was 21.9% (95% CI = 18.7-25.0%) among women. Among children, the infection-adjusted prevalence of VAD (<0.83 μmol RBP/L) was 35.0% (95% CI = 31.1-39.0%). In conclusion, VAD remains a public health problem in Cameroon. The RBP:ROH relationship should be considered in surveys using RBP to assess VA status, and use of population-specific cutoffs may be advisable.

Determinants of iron status and Hb in the Bangladesh population: the role of groundwater iron

“…‡Fe deficiency is defined as serum ferritin <15 ng/ml (49) . §Adjusted for elevated C-reactive protein (>10 mg/l) or elevated α 1 -acid glycoprotein (>1 g/l) by mathematical correction (18,19) . ||Fe-deficiency anaemia is defined as Hb <11·5 g/dl plus serum ferritin <15 ng/ml in children aged 6-11 years and as Hb <12 g/dl plus serum ferritin <15 ng/ml in children aged 12-14 years (49) .…”

“…Adjusting for infection Serum ferritin was adjusted for infection by estimating biomarkers of infection: CRP and AGP. The adjustment of serum ferritin for elevated CRP (>10·0 mg/l) (15)(16)(17) and AGP (>1·0 g/l) was done by calculating the correction factors following the methods described by Thurnham et al (18) and Engle-Stone et al (19) . Similarly correction factors for serum retinol and Zn were calculated and used to adjust the retinol and Zn levels in serum.…”

International Experiences in Assessing Vitamin A Status and Applying the Vitamin A-Labeled Isotope Dilution Method

“…However, in 2009 a national survey was done in preparation for a large-scale food fortifi cation program (mandatory fortifi cation of oil) and indicators of VA status and infl ammation were assessed before the fortifi cation was begun. Adjusted results showed that 35 % of children under 5 years had VAD, which thus remains a severe public health problem [15]. These results suggest that the efforts through the national supplementation program have not been suffi cient to improve VA status in the population's children.…”

Prevalence and Predictors of Vitamin a Deficiency Among Infants in Western Kenya Using a Cross-Sectional Analysis

“…However, a primary short-coming of RBP is the lack of universally acceptable cutoff for defining VAD, hence making comparisons and interpretations of results across different populations is complicated. For our study, we applied a cut-off of <0.825 µmol RBP/L for children (corresponding to <0.70 µmol retinol/L) [18]. Secondary limitation of RBP is ability to act as a negative acute phase protein; we adjusted for this effect of infection/inflammation by applying a CRP cut-off of >5.0mg /L.…”

“…The inter-assay and intra-assay CV of the assay were <10%. Definition of VA status was serum RBP concentration <0.825 µmol/L (biologically equivalent to <0.70 µmol/L retinol) [18].…”