Hans Verhoef

Hepcidin is the major predictor of erythrocyte iron incorporation in anemic African children

Iron supplementation strategies in the developing world remain controversial because of fears of exacerbating prevalent infectious diseases. Understanding the conditions in which iron will be absorbed and incorporated into erythrocytes is therefore important. We studied Gambian children with either postmalarial or nonmalarial anemia, who were given oral iron supplements daily for 30 days. Supplements administered on days 1 and 15 contained the stable iron isotopes 57Fe and 58Fe, respectively, and erythrocyte incorporation was measured in blood samples drawn 14 days later. We investigated how the iron-regulatory hormone hepcidin and other inflammatory/iron-related indices, all measured on the day of isotope administration, correlated with erythrocyte iron incorporation. In univariate analyses, hepcidin, ferritin, C-reactive protein, and soluble transferrin receptor (sTfR) strongly predicted incorporation of 57Fe given on day 1, while hepcidin, ferritin, and sTfR/log ferritin correlated with 58Fe incorporation. In a final multivariate model, the most consistent predictor of erythrocyte isotope incorporation was hepcidin. We conclude that under conditions of competing signals (anemia, iron deficiency, and infection), hepcidin powerfully controls use of dietary iron. We suggest that low-cost point-of-care hepcidin assays would aid iron supplementation programs in the developing world.

Efficacy of iron-fortified whole maize flour on iron status of schoolchildren in Kenya: a randomised controlled trial

BACKGROUND Sodium iron edetic acid (NaFeEDTA) might be a more bioavailable source of iron than electrolytic iron, when added to maize flour. We aimed to assess the effect, on childrens iron status, of consumption of whole maize flour fortified with iron as NaFeEDTA or electrolytic iron. METHODS 516 children, aged 3-8 years, from four schools in Marafa, Kenya, were randomly assigned to four groups. All were given the same amount of porridge five times a week. The porridge for one group was made from unfortified whole maize flour; for the other three groups it was fortified with either high-dose NaFeEDTA (56 mg/kg), low-dose NaFeEDTA (28 mg/kg), or electrolytic iron (56 mg/kg). Concentrations of haemoglobin, plasma ferritin, and transferrin receptor were analysed in samples taken at baseline and at the end of the 5-month intervention. The primary outcome was iron-deficiency anaemia. We analysed data on an intention-to-treat basis. This trial is registered with ClinicalTrials.gov, number NCT00386074. FINDINGS The prevalence of iron-deficiency anaemia in children given unfortified flour was 10%. Compared with placebo, the prevalence of iron-deficiency anaemia in children given flour fortified with high-dose NaFeEDTA, low-dose NaFeEDTA, and electrolytic iron changed by -89% (95% CI -97% to -49%), -48% (-77% to 20%), and 59% (-18% to 209%), respectively. Consumption of high-dose NaFeEDTA improved all measured iron-status indicators. Low-dose NaFeEDTA decreased the prevalence of iron deficiency but did not noticeably change the prevalence of anaemia. Electrolytic iron did not improve any of these iron-status indicators. Children who were iron-deficient at baseline benefited more from high-dose and low-dose NaFeEDTA than those with sufficient iron at baseline. INTERPRETATION Consumption of whole maize flour fortified with NaFeEDTA caused modest, dose-dependent improvements in childrens iron status. Fortification with electrolytic iron did not improve their iron status. Therefore, in high-phytate flours, NaFeEDTA is more suitable than electrolytic iron for supplementation of iron in the diet.

Intermittent administration of iron and sulfadoxine-pyrimethamine to control anaemia in Kenyan children: a randomised controlled trial

BACKGROUND Iron supplementation is recommended for children at high risk of anaemia, but its benefits may not outweigh the associated risk of malaria in areas of seasonal transmission. We investigated the effect on haemoglobin concentrations of intermittent administration of iron supplements and sulfadoxine-pyrimethamine in symptom-free children under intense health surveillance. METHODS In a trial of two by two factorial design, 328 anaemic Kenyan children were randomly assigned either iron or placebo and sulfadoxine-pyrimethamine or placebo (82 to each group). Primary outcomes were haemological indicators of iron status and inflammation at the end of the follow-up, and occurrence of malaria attacks. Morbidity surveillance consisted of medical examinations every 4 weeks, continuous passive case detection, and visits twice a week to community health-workers. Analyses were by intention to treat. FINDINGS After 12 weeks, the groups assigned iron plus sulfadoxine-pyrimethamine, iron alone, or sulfadoxine-pyrimethamine alone had higher haemoglobin concentrations than the group assigned placebo (treatment effect adjusted for prognostic factors at baseline: 11.1 g/L [95% CI 7.5 to 14.7]; 10.7 g/L [7.1 to 14.3]; and 3.1 g/L [-0.5 to 6.7]). Administration of iron plus sulfadoxine-pyrimethamine also lowered the proportion with anaemia from 100% at baseline to 36% at 12 weeks, and of iron deficiency from 66% at baseline to 8% at 12 weeks. Survival analysis showed no evidence of substantially increased risk of malaria after iron supplementation. INTERPRETATION Iron supplementation gives substantial health benefits, which may outweigh possible inherent risks caused by malaria. A larger study than ours is needed to assess benefits and risks of intermittent administration of sulfadoxine-pyrimethamine in reducing the incidence of malaria attacks in areas of seasonal malaria transmission.

Assessment of Urinary Concentrations of Hepcidin Provides Novel Insight into Disturbances in Iron Homeostasis during Malarial Infection

Disturbances in iron homeostasis are frequently observed in individuals with malaria. To study the effect of malaria and its treatment on iron homeostasis and to provide a mechanistic explanation for observed alterations in iron distribution, we studied the course of the iron regulatory hormone hepcidin in anemic Tanzanian children with febrile Plasmodium falciparum malaria. Before initiation of antimalarial treatment, urinary concentrations of hepcidin were strongly elevated and were associated with iron maldistribution, as was suggested by the presence of hypoferremia and high serum concentrations of ferritin. Antimalarial treatment resulted in a rapid decrease in urinary concentrations of hepcidin and reversal of the hypoferremia. Exploration of regulatory pathways of hepcidin production by analysis of iron, erythropoietic, and inflammatory indices suggested that reduced erythropoietic activity and inflammation stimulated hepcidin production. We conclude that high concentrations of hepcidin explain the observed disturbances in host iron homeostasis associated with malaria and may contribute to malarial anemia and an impaired erythropoietic response to iron supplementation.

Effect of supplementation with zinc and other micronutrients on malaria in Tanzanian children: a randomised trial

Hans Verhoef and colleagues report findings from a randomized trial conducted among Tanzanian children at high risk for malaria. Children in the trial received either daily oral supplementation with either zinc alone, multi-nutrients without zinc, multi-nutrients with zinc, or placebo. The investigators did not find evidence from this study that zinc or multi-nutrients protected against malaria episodes.

Expression of the Iron Hormone Hepcidin Distinguishes Different Types of Anemia in African Children

The iron hormone hepcidin correctly identifies African children in whom iron supplementation is most likely to be beneficial. Hepcidin Guides Iron Supplementation in African Children Anemia affects 300 million preschool children worldwide and has multiple causes including iron deficiency or infection. Dietary iron supplementation is used to combat anemia, but substantial concerns exist that iron can be harmful, in part by promoting infection. Iron is likely to preferentially benefit children with iron deficiency anemia, but identification of such children is challenging. Hepcidin is the hormone that regulates body iron levels and inhibits absorption of iron from the diet. Hepcidin concentrations are generally low in iron deficiency but are raised in iron-replete individuals and are also increased by infection. In a new study, Pasricha et al. set out to investigate whether hepcidin measurements would enable targeting of interventions to children who need iron but who are also able to absorb it. They tested this by measuring hepcidin in three cohorts of preschool African children from The Gambia and Tanzania. Single cutoffs of hepcidin concentrations efficiently identified children with iron deficiency, distinguished between iron deficiency anemia and anemia due to infection and inflammation, and predicted which children would incorporate >20% of an oral iron dose into their red blood cells. Thus, hepcidin is a critical determinant of iron homeostasis and may be a useful marker to guide diagnosis of anemia and enable screen-and-treat iron supplementation programs. Childhood anemia is a major global health problem resulting from multiple causes. Iron supplementation addresses iron deficiency anemia but is undesirable for other types of anemia and may exacerbate infections. The peptide hormone hepcidin governs iron absorption; hepcidin transcription is mediated by iron, inflammation, and erythropoietic signals. However, the behavior of hepcidin in populations where anemia is prevalent is not well established. We show that hepcidin measurements in 1313 African children from The Gambia and Tanzania (samples taken in 2001 and 2008, respectively) could be used to identify iron deficiency anemia. A retrospective secondary analysis of published data from 25 Gambian children with either postmalarial or nonmalarial anemia demonstrated that hepcidin measurements identified individuals who incorporated >20% oral iron into their erythrocytes. Modeling showed that this sensitivity of hepcidin expression at the population level could potentially enable simple groupings of individuals with anemia into iron-responsive and non–iron-responsive subtypes and hence could guide iron supplementation for those who would most benefit.

Defining Falciparum-Malaria-Attributable Severe Febrile Illness in Moderate-to-High Transmission Settings on the Basis of Plasma PfHRP2 Concentration

Background. In malaria-endemic settings, asymptomatic parasitemia complicates the diagnosis of malaria. Histidine-rich protein 2 (HRP2) is produced by Plasmodium falciparum, and its plasma concentration reflects the total body parasite burden. We aimed to define the malaria-attributable fraction of severe febrile illness, using the distributions of plasma P. falciparum HRP2 (PfHRP2) concentrations from parasitemic children with different clinical presentations. Methods. Plasma samples were collected from and peripheral blood slides prepared for 1435 children aged 6−60 months in communities and a nearby hospital in northeastern Tanzania. The study population included children with severe or uncomplicated malaria, asymptomatic carriers, and healthy control subjects who had negative results of rapid diagnostic tests. The distributions of plasma PfHRP2 concentrations among the different groups were used to model severe malaria-attributable disease. Results. The plasma PfHRP2 concentration showed a close correlation with the severity of infection. PfHRP2 concentrations of >1000 ng/mL denoted a malaria-attributable fraction of severe disease of 99% (95% credible interval [CI], 96%–100%), with a sensitivity of 74% (95% CI, 72%–77%), whereas a concentration of <200 ng/mL denoted severe febrile illness of an alternative diagnosis in >10% (95% CI, 3%–27%) of patients. Bacteremia was more common among patients in the lowest and highest PfHRP2 concentration quintiles. Conclusions. The plasma PfHRP2 concentration defines malaria-attributable disease and distinguishes severe malaria from coincidental parasitemia in African children in a moderate-to-high transmission setting.

Protection against Diarrhea Associated with Giardia intestinalis Is Lost with Multi-Nutrient Supplementation: A Study in Tanzanian Children

Background Asymptomatic carriage of Giardia intestinalis is highly prevalent among children in developing countries, and evidence regarding its role as a diarrhea-causing agent in these settings is controversial. Impaired linear growth and cognition have been associated with giardiasis, presumably mediated by malabsorption of nutrients. In a prospective cohort study, we aim to compare diarrhea rates in pre-school children with and without Giardia infection. Because the study was conducted in the context of an intervention trial assessing the effects of multi-nutrients on morbidity, we also assessed how supplementation influenced the relationship between Giardia and diarrhoea rates, and to what extent Giardia modifies the intervention effect on nutritional status. Methods and Findings Data were collected in the context of a randomized placebo-controlled efficacy trial with 2×2 factorial design assessing the effects of zinc and/or multi-micronutrients on morbidity (n = 612; height-for-age z-score <−1.5 SD). Outcomes measures were episodes of diarrhea (any reported, or with ≥3 stools in the last 24 h) and fever without localizing signs, as detected with health-facility based surveillance. Giardia was detected in stool by enzyme-linked immunosorbent assay. Among children who did not receive multi-nutrients, asymptomatic Giardia infection at baseline was associated with a substantial reduction in the rate of diarrhea (HR 0.32; 0.15–0.66) and fever without localizing signs (HR 0.56; 0.36–0.87), whereas no such effect was observed among children who received multi-nutrients (p-values for interaction 0.03 for both outcomes). This interaction was independent of age, HAZ-scores and distance to the research dispensary. There was no evidence that Giardia modified the intervention effect on nutritional status. Conclusion Although causality of the Giardia-associated reduction in morbidity cannot be established, multi-nutrient supplementation results in a loss of this protection and thus seems to influence the proliferation or virulence of Giardia or associated intestinal pathogens.

Defining falciparum malaria attributable severe febrile illness in moderate to high transmission settings based on plasma PfHRP2

Background. In malaria-endemic settings, asymptomatic parasitemia complicates the diagnosis of malaria. Histidine-rich protein 2 (HRP2) is produced by Plasmodium falciparum, and its plasma concentration reflects the total body parasite burden. We aimed to define the malaria-attributable fraction of severe febrile illness, using the distributions of plasma P. falciparum HRP2 (PfHRP2) concentrations from parasitemic children with different clinical presentations. Methods. Plasma samples were collected from and peripheral blood slides prepared for 1435 children aged 6−60 months in communities and a nearby hospital in northeastern Tanzania. The study population included children with severe or uncomplicated malaria, asymptomatic carriers, and healthy control subjects who had negative results of rapid diagnostic tests. The distributions of plasma PfHRP2 concentrations among the different groups were used to model severe malaria-attributable disease. Results. The plasma PfHRP2 concentration showed a close correlation with the severity of infection. PfHRP2 concentrations of >1000 ng/mL denoted a malaria-attributable fraction of severe disease of 99% (95% credible interval [CI], 96%–100%), with a sensitivity of 74% (95% CI, 72%–77%), whereas a concentration of <200 ng/mL denoted severe febrile illness of an alternative diagnosis in >10% (95% CI, 3%–27%) of patients. Bacteremia was more common among patients in the lowest and highest PfHRP2 concentration quintiles. Conclusions. The plasma PfHRP2 concentration defines malaria-attributable disease and distinguishes severe malaria from coincidental parasitemia in African children in a moderate-to-high transmission setting.

α+-Thalassemia Protects against Anemia Associated with Asymptomatic Malaria: Evidence from Community-Based Surveys in Tanzania and Kenya

BACKGROUND In hospital-based studies, alpha(+)-thalassemia has been found to protect against severe, life-threatening falciparum malaria. alpha(+)-Thalassemia does not seem to prevent infection or high parasite densities but rather limits progression to severe disease--in particular, severe malarial anemia. We assessed to what extent alpha(+)-thalassemia influences the association between mild, asymptomatic Plasmodium falciparum infection and hemoglobin concentration. METHODS The study was based on 2 community-based surveys conducted among afebrile children (0.5-8 years old; n=801) in Kenya and Tanzania. RESULTS Among children without inflammation (whole-blood C-reactive protein concentration <or=10 mg/L), P. falciparum infection was associated with only small reductions in hemoglobin concentration, and effects were similar across alpha-globin genotypes. By contrast, the reduction in hemoglobin concentration associated with P. falciparum infection accompanied by inflammation was larger and strongly depended on genotype (normal, -21.8 g/L; heterozygous, -16.7 g/L; and homozygous, -4.6 g/L). Relative to children with a normal genotype, this difference in effect was 5.1 g/L (95% confidence interval [CI], -1.0 to 11.1 g/L) for heterozygotes and 17.2 g/L (95% CI, 8.3 to 26.2 g/L) for homozygotes (estimates are adjusted for study site, age, height-for-age z score, and iron deficiency). CONCLUSIONS alpha(+)-Thalassemia limits the decline in hemoglobin concentration that is associated with afebrile infections, particularly those that are accompanied by inflammation.