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Am J Clin Nutr. 2017 Jul;106(Suppl 1):390S-401S. doi: 10.3945/ajcn.116.142166. Epub 2017 Jun 14.

Adjusting retinol-binding protein concentrations for inflammation: Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project.

Author information

1
Nutrition and Health Sciences Program, Laney Graduate School, and leila.larson@emory.edu.
2
Strengthening Partnerships, Results, and Innovations in Nutrition Globally, Arlington, VA.
3
Helen Keller International, Washington DC.
4
Rollins School of Public Health, Emory University, Atlanta, GA.
5
Department of Nutrition, University of California, Davis, CA.
6
Nutrition and Health Sciences Program, Laney Graduate School, and.
7
Nutrition Branch, CDC, Atlanta, GA.
8
GroundWork, Fläsch, Switzerland.
9
School of Medicine and Health Sciences, University of Papua New Guinea, Port Moresby, Papua New Guinea; and.
10
Independent Public Health Nutrition Consultant, Cambridge, United Kingdom.

Abstract

Background: The accurate estimation of the prevalence of vitamin A deficiency (VAD) is important in planning and implementing interventions. Retinol-binding protein (RBP) is often used in population surveys to measure vitamin A status, but its interpretation is challenging in settings where inflammation is common because RBP concentrations decrease during the acute-phase response.Objectives: We aimed to assess the relation between RBP concentrations and inflammation and malaria in preschool children (PSC) (age range: 6-59 mo) and women of reproductive age (WRA) (age range: 15-49 y) and to investigate adjustment algorithms to account for these effects.Design: Cross-sectional data from 8 surveys for PSC (n = 8803) and 4 surveys for WRA (n = 4191) from the Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project were analyzed individually and combined with the use of a meta-analysis. Several approaches were explored to adjust RBP concentrations in PSC in inflammation and malaria settings as follows: 1) the exclusion of subjects with C-reactive protein (CRP) concentrations >5 mg/L or α-1-acid glycoprotein (AGP) concentrations >1 g/L, 2) the application of arithmetic correction factors, and 3) the use of a regression correction approach. The impact of adjustment on the estimated prevalence of VAD (defined as <0.7 μmol/L) was examined in PSC.Results: The relation between estimated VAD and CRP and AGP deciles followed a linear pattern in PSC. In women, the correlations between RBP and CRP and AGP were too weak to justify adjustments for inflammation. Depending on the approach used to adjust for inflammation (CRP+AGP), the estimated prevalence of VAD decreased by a median of 11-18 percentage points in PSC compared with unadjusted values. There was no added effect of adjusting for malaria on the estimated VAD after adjusting for CRP and AGP.Conclusions: The use of regression correction (derived from internal data), which accounts for the severity of inflammation, to estimate the prevalence of VAD in PSC in regions with inflammation and malaria is supported by the analysis of the BRINDA data. These findings contribute to the evidence on adjusting for inflammation when estimating VAD with the use of RBP.

KEYWORDS:

anemia; inflammation; meta-analysis; nutritional assessment; retinol-binding protein; vitamin A deficiency

PMID:
28615251
PMCID:
PMC5490644
DOI:
10.3945/ajcn.116.142166
[Indexed for MEDLINE]
Free PMC Article

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