Relationship of the availability of micronutrient powder with iron status and hemoglobin among women and children in the Kakuma Refugee Camp, Kenya.

BACKGROUND: Micronutrient powder is a potential strategy to improve iron status and reduce anemia in refugee populations. OBJECTIVE: To evaluate the effect of the availability of home fortification with a micronutrient powder containing 2.5 mg of sodium iron ethylenediaminetetraacetate (NaFeEDTA) on iron status and hemoglobin in women and children in the Kakuma Refugee Camp in northwest Kenya. METHODS: Hemoglobin and soluble transferrin receptor were measured in 410 children 6 to 59 months of age and 458 women of childbearing age at baseline (just before micronutrient powder was distributed, along with the regular food ration) and at midline (6 months) and endline (13 months)follow-up visits. RESULTS: At the baseline, midline, and endline visits, respectively, the mean (+/- SE) hemoglobin concentration in women was 121.4 +/- 0.8, 120.8 +/- 0.9, and 120.6 +/- 1.0 g/L (p = .42); the prevalence of anemia (hemoglobin < 120 g/L) was 42.6%, 41.3%, and 41.7% (p = .92); and the mean soluble transferrin receptor concentration was 24.1 +/- 0.5, 20.7 +/- 0.7, and 20.8 +/- 0.7 nmol/L (p = .0006). In children, the mean hemoglobin concentration was 105.7 +/- 0.6, 109.0 30322 1.5, and 105.5 +/- 0.3 g/L (p = .95), respectively; the prevalence of anemia (hemoglobin < 110 g/L) was 55.5%, 52.3%, and 59.8% (p = .26); and the mean soluble transferrin receptor concentration was 36.1 +/- 0.7, 29.5 +/- 1.9, and 28.4 +/- 3.2 nmol/L (p = .02), in models that were adjusted for age using least squares means regression. CONCLUSIONS: In children and in women of childbearing age, the availability of micronutrient powder was associated with a small improvement in iron status but no significant change in hemoglobin in this refugee camp setting.

Vitamin A dynamics in breastmilk and liver stores: a life history perspective.

OBJECTIVES: Newborns are dependent on breastmilk vitamin A for building hepatic stores of vitamin A that will become critical for survival after weaning. It has been documented that vitamin A concentrations in breastmilk decline across the first year postpartum in both well-nourished and malnourished populations. The reason for this decline has been assumed to be a sign of concurrently depleting maternal hepatic stores. This study investigates this assumption to clarify why the decline occurs, drawing on life history theory. METHODS: A cross sectional survey was conducted among lactating mothers in Kenya in 2006. Data were used to examine (1) the relationship between liver vitamin A and time, (2) if the relationship between milk and liver vitamin A varies by time, and (3) by maternal parity. RESULTS: The relationship between liver vitamin A and time fits the quadratic pattern with marginal significance (P = 0.071, n = 192); the liver vitamin A declined during early postpartum then recovered in late postpartum time, controlling covariates. The milk-liver vitamin A relationship varied by postpartum time periods (P = 0.03) and by maternal parity (P = 0.005). Mothers in earlier postpartum or higher parity had a stronger positive relationship between milk and liver vitamin A than mothers in later postpartum or lower parity. CONCLUSIONS: Our observations are consistent with life history tradeoffs and negate the assumption that maternal hepatic and milk vitamin A decline together. Rather, maternal liver vitamin A has a dynamic relationship with milk vitamin A, particularly depending on postpartum time and maternal parity.

Assessment of the relative dose-response test based on serum retinol-binding protein instead of serum retinol in determining low hepatic vitamin A stores.

BACKGROUND: The relative dose-response (RDR) test, which measures the percentage of change in serum retinol concentration in response to an oral vitamin A (VA) dose, is a functional reference method to assess low hepatic VA stores. However, problems due to the relative instability of retinol, which is measured in the traditional RDR test, could be circumvented if retinol-binding protein (RBP), a more stable marker of VA, could be measured instead of retinol to provide the RDR value. OBJECTIVE: The objective was to compare classification of VA status assessed by retinol-RDR with that assessed by using RBP-RDR. DESIGN: With the use of serum samples from 57 lactating women in northern Kenya collected in August-September 2006, we assessed the accuracy of RBP-RDR in predicting low hepatic VA stores through receiver operator characteristic (ROC) analysis using retinol-RDR values as the gold standard. By using regression analysis, we explored the effects of 1) body mass index (BMI) on RBP-RDR performance and 2) the oral VA dose on the retinol-RBP molar ratio. RESULTS: The classificatory accuracy of RBP-RDR was low to moderate (n = 50; ROC area: 0.56-0.72) depending on the cutoffs used. RBP-RDR systematically overestimated VA deficiency with higher BMI, although it was superior to a single measurement of serum retinol. The discrepancy between RBP-RDR and retinol-RDR appears to originate in a retinol concentration-dependent alteration of the retinol-RBP molar ratio triggered by the oral dose. CONCLUSIONS: RBP-RDR has the potential to serve as a moderately accurate surrogate measure of retinol-RDR if the variation associated with BMI is understood and adjusted. Further studies should clarify the dynamics of the retinol-RBP molar ratio and its link to RBP-RDR performance.

Retinol-binding protein stability in dried blood spots.

BACKGROUND: Retinol-binding protein (RBP) is accepted as a surrogate biochemical marker for retinol to determine vitamin A (VA) status. A recently developed enzyme immunoassay for RBP uses serum or whole blood stored as dried blood spots (DBS). However, the stability of RBP in DBS has not been examined. METHODS: RBP stability was studied in a laboratory and in field conditions in northern Kenya. For the laboratory study, 63 DBS collected by finger prick and stored sealed in a plastic bag with desiccant were exposed to 1 of 5 time/storage-temperature treatments: (a) baseline, (b) 30 degrees C/7 days, (c) 30 degrees C/14 days, (d) 30 degrees C/28 days, and (e) 4 degrees C/38 days. Baseline RBP concentrations were compared to those obtained after the storage treatments. For the field study, 50 paired DBS and serum specimens were prepared from venous blood obtained in northern Kenya. DBS were stored in a sealed plastic bag with desiccant at ambient temperature (12 degrees C-28 degrees C) for 13-42 days, and sera were stored at -20 degrees C to -70 degrees C. Recovered RBP concentrations were compared with serum retinol for stability, correlation, sensitivity, and specificity. RESULTS: RBP in DBS stored in the laboratory at 30 degrees C remained stable for 2-4 weeks, but specimens stored at 4 degrees C for 38 days produced values below baseline (P = 0.001). DBS stored under field conditions remained stable for 2-6 weeks, as demonstrated by good correlation with serum retinol, a result that suggests that RBP in DBS will have good sensitivity and specificity for predicting VA deficiency. CONCLUSION: RBP in DBS can withstand storage at a relatively high ambient temperature and thus facilitate accurate VA assessments in populations in locations where serum collection and storage are unfeasible.