Dataset Information

Serum retinol concentrations demonstrate high specificity after correcting for inflammation but questionable sensitivity compared with liver stores calculated from isotope dilution in determining vitamin A deficiency in Thai and Zambian children.

ABSTRACT: BACKGROUND:The WHO estimates that 190 million preschool children have vitamin A deficiency (VAD). Serum retinol (SR) concentration is a common indicator of vitamin A (VA) status, but SR is homeostatically controlled and suppressed during inflammation, which may lead to misdiagnosis. OBJECTIVE:The sensitivity and specificity of SR compared with VA total liver reserves (TLRs) were evaluated for VAD in children from Thailand (n = 37) and Zambia (n = 128). SR was adjusted for inflammation in the Zambian children. DESIGN:Each child was classified as VA-deficient or not based on cutoffs of <0.1 ?mol VA/g liver with the use of retinol isotope dilution and <0.7 ?mol/L for SR concentrations. Four categories of infection status in the Zambian children were based on elevated C-reactive protein (CRP) and ?1-acid glycoprotein (AGP). Sensitivity and specificity were calculated with the use of unadjusted and inflammation marker-adjusted SR cutoffs. RESULTS:VAD was 65% and 0% according to TLRs and SR, respectively, in Thai children and 0% and 17%, respectively, in Zambian children. No true positive VAD cases occurred; thus, sensitivity was 0% and indeterminable, respectively; specificity was 100% and 82.8%, respectively. CRP was elevated in 26.6% of Zambian children, whereas 97.7% had elevated AGP, categorizing them as having no infection (2.3%) or in early (26.6%) or late (58.6%) convalescence. With the use of marker-adjusted SR cutoffs of 0.6 ?mol/L for late convalescence and 0.5 ?mol/L for early convalescence, the adjusted prevalence of SR deficiency was 2.3%, increasing specificity to 97.3%. CONCLUSIONS:No cases of VAD were identified by both TLRs and SR (true positives) in Thai or Zambian children. Specificity of SR to evaluate VAD was high, but additional research is needed to investigate sensitivity. Adjusting SR cutoffs for inflammation improved specificity by reducing false positives. SR as a VAD indicator may depend on infection rates, which should be taken into consideration. These studies were registered at clinicaltrials.gov as NCT01061307 (for Thailand) and NCT01814891 (for Zambia).

SUBMITTER: Suri DJ

PROVIDER: S-EPMC6546224 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Serum retinol concentrations demonstrate high specificity after correcting for inflammation but questionable sensitivity compared with liver stores calculated from isotope dilution in determining vitamin A deficiency in Thai and Zambian children.

Suri Devika J DJ Tanumihardjo Jacob P JP Gannon Bryan M BM Pinkaew Siwaporn S Kaliwile Chisela C Chileshe Justin J Tanumihardjo Sherry A SA

The American journal of clinical nutrition 20151007 5

<h4>Background</h4>The WHO estimates that 190 million preschool children have vitamin A deficiency (VAD). Serum retinol (SR) concentration is a common indicator of vitamin A (VA) status, but SR is homeostatically controlled and suppressed during inflammation, which may lead to misdiagnosis.<h4>Objective</h4>The sensitivity and specificity of SR compared with VA total liver reserves (TLRs) were evaluated for VAD in children from Thailand (n = 37) and Zambia (n = 128). SR was adjusted for inflamma ...[more]

PMID: 26447158

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Project description:Background:Retinol isotope dilution (RID) indirectly estimates vitamin A (VA) status. Multicompartment modeling of RID data is used to refine study designs and equations to calculate VA stores. Previous studies suggest that VA in slowly turning over pools is not traced if follow-up is not long enough; however, shorter RID studies are being investigated. Few long-term models have been published. Objective:We determined the effect of time on mathematical models of VA kinetics, model parameters, and outcomes. Methods:In this longitudinal study, women (mean ± SD age: 22 ± 3 y; n = 7) were given 2.0 µmol [14,15]-13C2-retinyl acetate. Blood samples were staggered from 4 h to 152 d; the fraction of dose in serum was modeled with compartmental models. Four model-time categories were created: full models that used all data (median: 137 d; range 97-152 d) and truncated shorter studies of 14, 27, and 52 d (range: 42-62 d). Outcomes included number of compartments to adequately model serum data, kinetic parameters, total traced VA mass, and time-to-dose equilibration. To gain insight into longer follow-up, an additional participant was given 17.5 µmol 13C4-VA, and data were modeled as long as enrichment was above baseline (5 y). Results:Longer follow-up times affected kinetic parameters and outcomes. Compared with the 14-d models, long-term full models required an additional compartment for adequate fit (14.3% compared with 100%; P = 0.0056) and had longer [median (quartile 1, quartile 3)] whole-body half-life [15.0 d (10.5, 72.6 d) compared with 135 d (115, 199 d); P = 0.0006], time-to-dose equilibration [3.40 d (3.14, 6.75 d) compared with 18.9 d (11.2, 25.7 d); P < 0.0001], and total traced mass [166 µmol VA (162, 252 µmol VA) compared with 476 µmol VA (290, 752 µmol VA); P = 0.0031]. Conclusions:Extended RID sampling alters numerous mathematically modeled, time-dependent outcomes in women. Length of study should be considered when using mathematical models for calculating total-body VA stores or kinetic parameters related to VA turnover. This study is registered at www.clinicaltrials.gov as NCT03248700.

Project description:BackgroundBiomarkers of micronutrient status are needed to best define deficiencies and excesses of essential nutrients.ObjectiveWe evaluated several supporting biomarkers of vitamin A status in Zambian children to determine whether any of the biomarkers were consistent with high liver retinol stores determined by using retinol isotope dilution (RID).DesignA randomized, placebo-controlled, biofortified maize efficacy trial was conducted in 140 rural Zambian children from 4 villages. A series of biomarkers were investigated to better define the vitamin A status of these children. In addition to the assessment of total-body retinol stores (TBSs) by using RID, tests included analyses of serum carotenoids, retinyl esters, and pyridoxal-5'-phosphate (PLP) by using high-pressure liquid chromatography, retinol-binding protein by using ELISA, and alanine aminotransferase (ALT) activity by using a colorimetric assay.ResultsChildren (n = 133) were analyzed quantitatively for TBSs by using RID. TBSs, retinyl esters, some carotenoids, and PLP differed by village site. Serum carotenoids were elevated above most nonintervened reference values for children. α-Carotene, β-carotene, and lutein values were >95th percentile from children in the US NHANES III, and 13% of children had hypercarotenemia (defined as total carotenoid concentration >3.7 μmol/L). Although only 2% of children had serum retinyl esters >10% of total retinol plus retinyl esters, 16% of children had >5% as esters, which was consistent with high liver retinol stores. Ratios of serum retinol to retinol-binding protein did not deviate from 1.0, which indicated full saturation. ALT activity was low, which was likely due to underlying vitamin B-6 deficiency, which was confirmed by very low serum PLP concentrations.ConclusionsThe finding of hypervitaminosis A in Zambian children was supported by high circulating concentrations of carotenoids and mildly elevated serum retinyl esters. ALT-activity assays may be compromised with co-existing vitamin B-6 deficiency. Nutrition education to improve intakes of whole grains and animal-source foods may enhance vitamin B-6 status in Zambians.

Project description:This analysis was performed in Zambian children who had a high prevalence of hypervitaminosis A, defined as >?1.0 ?mol retinol/g liver. Bone parameters included markers of bone formation (P1NP), bone resorption (CTX), parathyroid hormone, calcium, vitamin A, and vitamin D. Low dietary vitamin A intake increased P1NP. PURPOSE:Vitamin A (VA) interacts with bone health, but mechanisms require clarification. In countries where multiple interventions exist to eradicate VA deficiency, some groups are consuming excessive VA. Bone metabolism and inflammatory parameters were measured in Zambian children who had high prevalence of hypervitaminosis A determined by 13C-retinol isotope dilution. METHODS:Children (n?=?143), 5 to 7 years, were recruited into a placebo-controlled biofortified orange maize feeding study for 90 days. Bone turnover (P1NP and CTX) and inflammatory (C-reactive protein (CRP) and alpha-1-acid glycoprotein) biomarkers were measured in fasting blood samples before and/or after intervention with the following: (1) VA at the recommended dietary allowance (400 ?g retinol activity equivalents/day (as retinyl palmitate)), (2) maize enhanced with the provitamin A carotenoid ?-carotene (2.86 mg/day), or (3) a placebo. Parathyroid hormone, calcium, and 25(OH)-vitamin D were measured at end line. RESULTS:Bone formation, as measured by P1NP, increased (P?<?0.0001) in the placebo group who consumed low preformed VA during the intervention. Bone resorption, measured by CTX, was not affected. P1NP and CTX were negatively associated with inflammation, most strongly with CRP. Serum calcium did not differ among groups and was low (7.29?±?0.87 ?g/dL). Serum 25(OH) D did not differ among groups (54.5?±?15 nmol/L), with 91% <?75 nmol/L and 38% <?50 nmol/L. CONCLUSIONS:Reduction of dietary preformed VA in Zambian children for 4 months improved bone formation. Chronic consumption of preformed VA caused hypervitaminosis A and may impair bone formation. In children, this could be associated with failure to accrue optimal peak bone mass. TRIAL REGISTRATION:The NIH Clinical Trial registry number is NCT01814891; https://clinicaltrials.gov/ct2/show/NCT01814891 .

Dataset Information

Serum retinol concentrations demonstrate high specificity after correcting for inflammation but questionable sensitivity compared with liver stores calculated from isotope dilution in determining vitamin A deficiency in Thai and Zambian children.

Publications

Serum retinol concentrations demonstrate high specificity after correcting for inflammation but questionable sensitivity compared with liver stores calculated from isotope dilution in determining vitamin A deficiency in Thai and Zambian children.

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