Application of Retinol-Binding Protein Enzyme Immunoassay to Dried Blood Spots to Assess Vitamin A Deficiency in a Population-Based Survey: The Uganda Demographic and Health Survey 2006

Baingana, Rhona; Matovu, Denis Kasozi; Garrett, Dean

doi:10.1177/156482650802900406

Cited by 21 publications

(25 citation statements)

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“…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. (3) . The VAD prevalence estimate in children was 20?4 % (4) .…”

Section: Introductionmentioning

confidence: 99%

“…We previously reported on the assessment of the prevalence of VAD in the UDHS 2006 using an enzyme immunoassay to measure the levels of RBP in DBS (3) . However, we did not measure any APP at that time.…”

Section: Introductionmentioning

confidence: 99%

“…Regardless of the approach, the consensus is that including measurements of APP will improve the interpretation of results when vitamin A status is assessed using retinol and RBP. The application of a correction factor is a logical approach for interpreting levels of serum retinol (12)(13)(14) and other nutritional biomarkers (16)(17)(18) that are influenced by infection, when these indicators are measured in populations with a high burden of infection.We previously reported on the assessment of the prevalence of VAD in the UDHS 2006 using an enzyme immunoassay to measure the levels of RBP in DBS (3) . However, we did not measure any APP at that time.…”

mentioning

confidence: 99%

“…A similar validation experiment for RBP had already demonstrated an excellent correlation between RBP values of matching serum and DBS samples (r 5 0?79, P , 0?00001). A correction factor of 1?44 was used to correct all DBS RBP values (3) . …”

mentioning

confidence: 99%

“…The filter paper cards were labelled and dried overnight in opaque boxes containing desiccant (Minipak; Multisorb Technologies, Buffalo, NY, USA), packed individually in low-gas-permeable plastic zip-lock bags containing desiccant and humidity indicator cards, and stored at 2208C until analysis. Analysis for RBP using enzyme immunoassay (SCANLISA R RBP Assay; Scimedx Corporation, Denville, NJ, USA) was carried out in 2006 and is described elsewhere (3) . In preparation for CRP analysis, all 2460 DBS were checked individually for stability (humidity status) and adequacy of spots.…”

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confidence: 99%

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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

Baingana

Matovu-Kasozi

Garrett

2012

Public Health Nutr.

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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) mmol/l, 1?26 (95 % CI 1?20, 1?33) mmol/l and 1?12 (95 % CI 1?07, 1?17) mmol/l, respectively, before correction. Correction increased mean RBP in Group B to 1?26 (95 % CI 1?21, 1?31) mmol/l. The prevalence of vitamin A deficiency (RBP , 0?825 mmol/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. (3) . The VAD prevalence estimate in children was 20?4 % (4) . Circulating concentrations of serum retinol (5)(6)(7) and RBP (8) decline in response to the acute-phase response and may not adequately reflect vitamin A status. These changes, which are an integral part of the acute-phase response, reflect decreased synthesis of RBP and increased excretion of retinol in urine (9,10) . Because levels of circulating acute-phase proteins (APP) can aid in the interpretation of low serum retinol levels, the simultaneous measurement of retinol and one or more APP is recommended (5)(6)(7)(11)(12)(13) . There is currently no consensus on how to correct retinol concentrations for the influence of the acute-phase response. Paracha et al. (11) proposed the application of new cut-offs for low and deficient retinol concentrations for children in whom a 1 -antichymotrypsin and a 1 -acid glycoprotein concentrations were elevated. In the approach proposed by Thurnham et al., individuals with normal APP levels provide the reference group for whom it is assumed that diet is the main factor responsible for the concentration of retinol. The median retinol value for the reference group is divided by the respective median values for groups at different stages of the acutephase response. Correction factors thus obtained were applied to apparently healthy HIV-1-positive adults with raised APP; the proportion with low...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%