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The importance of controlling for the acute-phase response in the population-based assessment of vitamin A status: a study in children of pre-school age in Uganda.
Authors: Baingana R, Matovu-Kasozi D, Garrett D.
Source: Public Health Nutrition, 1:1-8. [Epub ahead of print], DOI: 10.1017/S1368980012004351, Published online: 01 October 2012
Topic(s): Child health
Vitamin A
Country: Africa
Published: OCT 2012
Abstract: OBJECTIVE: To improve estimates of vitamin A deficiency in children of pre-school age in the 2006 Uganda Demographic and Health Survey (UDHS 2006). DESIGN: A cross-sectional study in which dried blood spot samples were analysed for C-reactive protein (CRP). Retinol-binding protein (RBP) had previously been analysed using a commercial enzyme immunoassay. SETTING: A population-based study in Uganda. SUBJECTS: A systematically selected subset of the dried blood spot samples collected from children aged 6-59 months for UDHS 2006. Children were categorized into 'normal CRP' (Group A) and 'raised CRP' (Group B) using a CRP cut-off of 5 mg/l. A correction factor was calculated to adjust the Group B RBP values for the influence of the acute-phase response. RESULTS: Geometric mean CRP was 6·2 (95 % CI 5·5, 7·0) mg/l, 1·6 (95 % CI 1·5, 1·8) mg/l and 17·9 (95 % CI 16·4, 19·6) mg/l in all children, in Group A and in Group B, respectively. Geometric mean RBP in all children, in Group A and in Group B was 1·18 (95 % CI 1·14, 1·22) µmol/l, 1·26 (95 % CI 1·20, 1·33) µmol/l and 1·12 (95 % CI 1·07, 1·17) µmol/l, respectively, before correction. Correction increased mean RBP in Group B to 1·26 (95 % CI 1·21, 1·31) µmol/l. The prevalence of vitamin A deficiency (RBP < 0·825 µmol/l) reduced from 18·4 % (95 % CI 17·2, 23·0 %) to 13·9 % (95 % CI 11·3, 16·5 %). CONCLUSIONS: Correcting for the acute-phase response significantly reduced the prevalence of vitamin A deficiency; thus, the acute-phase response should be considered when vitamin A status is assessed using RBP in order to improve population-level estimates of vitamin A deficiency.