Usefulness of serum transferrin receptor and serum ferritin in diagnosis of iron deficiency in infancy

Iron Deficiency is Related to Depressive Symptoms in United States Nonpregnant Women of Reproductive Age: A Cross-Sectional Analysis of NHANES 2005-2010

BACKGROUND

Findings of the association between iron status and depressive symptoms in nonpregnant women of reproductive age (WRA) are equivocal, limited by a small sample size, or did not consistently control for confounders.

OBJECTIVE

We tested the association between iron status and depressive symptoms in WRA with the NHANES data (2005-2010).

METHODS

Nonpregnant WRA (20-44 y) with complete data on iron (ferritin and transferrin receptor (TfR)) and anemia (hemoglobin) biomarkers, depressive symptoms (Patient Health Questionnaire-9), and sociodemographic variables were included. Logistic and negative binomial regressions were used to estimate presence (odds ratios) and magnitude (prevalence ratios), respectively, for depressive symptoms by iron deficiency (ID)/anemia/ID anemia in the total sample and stratified by poverty:income ratio (≤ 1.85 or >1.85).

RESULTS

Among 2516 females, the prevalence of ID was 8 to 16% (depending on the iron biomarker used), of anemia 8%, of which 52 to 65% were also ID. The prevalence of depressive symptoms was 10%. Crude logistic models showed that females with ID (TfR ≥ 8.3 mg/L or body iron <0 mg/kg) from the total sample had 1.82 (95% confidence interval [CI]: 1.24, 2.68) and 1.62 (95% CI: 1.05, 2.48), respectively, higher odds of depressive symptoms than females with iron sufficiency; these associations were attenuated after adjustments for confounders. Adjusted negative binomial models showed that females with ID (TfR ≥ 8.3 mg/L) from the total and low-income samples showed 1.19 (95% CI: 1:00, 1.40) and 1.27 (95% CI: 1.03, 1.58), respectively, higher prevalence ratios of depressive symptoms scores than females with iron sufficiency.

CONCLUSIONS

These nationally representative data indicate that nonpregnant WRA with ID (based on high TfR) in the United States have higher prevalence of somatic depressive symptoms scores than those with iron sufficiency, especially if they are of low income.

Reticulocyte hemoglobin content changes after treatment of anemia of prematurity

BACKGROUND

Iron deficiency during infancy is associated with poor neurological development, but iron overload causes severe complications. Appropriate iron supplementation is therefore vital. Reticulocyte hemoglobin content (RET-He) provides a real-time assessment of iron status and chracterezes hemoglobin synthesis in preterm infants. However, the existing literature lacks detailed reports assessing chronological changes in RET-He. The aim of this study was to assess the chronological changes in RET-He during oral iron dietary supplementation, and concomitant therapy with recombinant human erythropoietin (rHuEPO) in preterm very low birthweight infants.

METHODS

Very low birthweight infants, admitted to our neonatal intensive care unit were analyzed retrospectively. Hemoglobin (Hb), reticulocyte percentage (Ret), mean corpuscular volume, RET-He, serum iron (Fe), and serum ferritin were recorded. Data at birth (T0), the initial day of rHuEPO therapy (T1), the initial day of oral iron supplementation (T2), 1-2 weeks (T3), 3-4 weeks (T4), 5-6 weeks (T5), and 7-8 weeks (T6) from the initial day of oral iron supplementation were extracted, and their changes over time were examined.

RESULTS

Reticulocyte hemoglobin content was highest at birth and declined rapidly thereafter, especially after starting rHuEPO therapy. There was no upward trend in RET-He after the initiation of oral iron supplementation, with a slower increase during 5-6 weeks after the initiation of iron therapy.

CONCLUSIONS

During the treatment of anemia of prematurity, low RET-He levels may be prolonged. Anemia of prematurity should therefore be assessed and treated on a case-by-case basis, while considering the iron metabolic capacity of preterm infants.

Effect of Sepsis on Iron Parameters in a Population with High Prevalence of Malnutrition and Iron Deficiency: A Cross-Sectional Case-Control Pilot Study

There is lack of data on iron metabolism in critically ill sepsis children from population with high prevalence of iron deficiency (ID). The study was designed to study impact of sepsis on iron parameters in children with ID. Sepsis patients (age 6-59 months) and their apparently healthy sibling/cousin as controls were enrolled in this case-control pilot study. Serum iron, TIBC, transferrin saturation, ferritin and sTfR were measured in the two groups. sTfR-Ferritin index was calculated. Patients (n = 134) were significantly underweight compared to controls (n = 54) (WAZ score < - 2; 58% vs. 28%; p < 0.001). Serum iron and sTfR (mg/L) were lower [71.5 (51.0, 115.0) vs. 87.0 (64.5, 130.5), p = 0.068; 3.1 (2.1, 4.5) vs. 3.5 (2.8, 4.8), p = 0.026 respectively] while serum ferritin was higher [229 (94, 484.5) vs. 22 (9.2, 51); p < 0.001] in patients compared to controls. sTfR-Ferritin index was lower in patients [1.3 (0.8, 2.3) vs. 2.5 (1.8, 4.5); p < 0.001]. ROC AUC (patients vs. controls) were 0.89 (95% CI 0.83-0.95) and 0.76 (95% CI 0.68-0.85) for ferritin and sTfR-ferritin index respectively. Survivors and non-survivors were similar in terms of iron parameters. Sepsis-induced alterations in iron parameters among ID children are complex. Qualitatively it is similar (with quantitative differences) to non-ID adult population. Lack of correlation of iron parameters with mortality may be due to ID-associated immune dysfunction.

Soluble Transferrin Receptor during infancy and reference intervals for the Roche Cobas platform

INTRODUCTION

Infant iron status assessments may be difficult to interpret due to infections. The soluble transferrin receptor (sTfR) has been suggested as a biomarker mainly unaffected by the acute phase response. Reference intervals reflecting dynamics of infant growth first year in life are not well established.

METHODS

The sTfR and CRP concentrations were measured in samples from 451 term infants with the Roche Cobas platform in umbilical cord, at 48-96 hours, 4 and 12 months. Reference values were constructed as the 2.5th and 97.5th percentiles. The relationship between CRP concentrations >1 mg/L and sTfR was tested by Kendall correlation.

RESULTS

Reference intervals for girls and boys were 2.4-9.5 mg/L at birth, 2.9-8.4 mg/L at 48-96 hours, 2.6-5.7 mg/L at 4 months and 3.0-6.3 mg/L at 12 months. No differences between sexes were observed except for at 4 months. sTfR did not covariate with CRP concentrations >1 mg/L except in 48-96 hours samples.

CONCLUSION

This study reports reference intervals for sTfR from birth to 12 months of age in a large group of infants in a low-risk area for iron deficiency. sTfR might add value to infant iron status diagnostics since no covariation with CRP was found at birth, at 4 months or at 12 months.

BODY IRON STATUS INDICATORS AND INFLAMMATION INDICATORS DURING INFLAMMATORY BOWEL DISEASE THERAPY IN CHILDREN AND ADOLESCENTES

BACKGROUND

The treatment of patients with inflammatory bowel disease (IBD) consists of the induction and maintenance remission of the disease. Iron status indicators would be useful for the diagnosis of iron deficiency anemia, whereas the inflammation indicators would be for the diagnosis of chronic disease anemia.

OBJECTIVE

To assess body iron status indicators and inflammation indicators during the treatment of IBD, consisted of conventional or infliximab therapy in children and adolescents.

METHODS

A case-control study of a sample of 116 individuals, of which 81 patients with IBD, 18 of them receiving conventional therapy, 20 infliximab therapy, and 43 who were in remission of the disease, and 35 healthy (control group) children and adolescents. Iron status and inflammation indicators were investigated at baseline, and 2 and 6 months of both therapies - conventional and infliximab.

RESULTS

The mean age was 12.1±4.3 years. At baseline, both groups - conventional therapy and infliximab - presented significant differences in most markers studied compared to the control group. After 2 months of conventional therapy, hemoglobin and serum iron levels were lower than those of the control group; and red cells distribution width (RDW), total iron-binding capacity, transferrin receptor/ferritin ratio, and interleukin-6 were higher than the control group. After 2 months of infliximab treatment, hemoglobin and serum iron levels were lower than those of the control group; and RDW, soluble transferrin receptor, soluble transferrin receptor/ferritin ratio, and interleukin-6 were higher than the control group. After 6 months of conventional therapy, hemoglobin and serum iron levels were lower than those of the control group, and RDW and interleukin-6 were higher than those of the control group. After 6 months of infliximab treatment, the hemoglobin and serum iron levels were lower than the control group, and RDW, soluble transferrin receptor, soluble transferrin receptor/ferritin ratio, erythrocyte sedimentation rate, and platelets were higher than the control group. Regarding patients under treatment for at least one year (remission group), all markers studied, except transferrin, were similar to the control group.

CONCLUSION

In conclusion, there were some contradictions among the different body iron status indicators and inflammation indicators at two and 6 months of treatment with conventional and infliximab therapy, however after one year of treatment, as shown by the remission group, all indicators studied, except transferrin, were similar to healthy children and adolescents.

Biomarkers of Nutrition for Development (BOND)-Iron Review

This is the fifth in the series of reviews developed as part of the Biomarkers of Nutrition for Development (BOND) program. The BOND Iron Expert Panel (I-EP) reviewed the extant knowledge regarding iron biology, public health implications, and the relative usefulness of currently available biomarkers of iron status from deficiency to overload. Approaches to assessing intake, including bioavailability, are also covered. The report also covers technical and laboratory considerations for the use of available biomarkers of iron status, and concludes with a description of research priorities along with a brief discussion of new biomarkers with potential for use across the spectrum of activities related to the study of iron in human health.The I-EP concluded that current iron biomarkers are reliable for accurately assessing many aspects of iron nutrition. However, a clear distinction is made between the relative strengths of biomarkers to assess hematological consequences of iron deficiency versus other putative functional outcomes, particularly the relationship between maternal and fetal iron status during pregnancy, birth outcomes, and infant cognitive, motor and emotional development. The I-EP also highlighted the importance of considering the confounding effects of inflammation and infection on the interpretation of iron biomarker results, as well as the impact of life stage. Finally, alternative approaches to the evaluation of the risk for nutritional iron overload at the population level are presented, because the currently designated upper limits for the biomarker generally employed (serum ferritin) may not differentiate between true iron overload and the effects of subclinical inflammation.

[Biological diagnosis of iron deficiency in children]

Measurement of serum ferritin (SF) is currently the laboratory test recommended for diagnosing iron deficiency. In the absence of an associated disease, a low SF value is an early and highly specific indicator of iron deficiency. The WHO criteria proposed to define depleted storage iron are 12μg/L for children under 5 years and 15μg/L for those over 5 years. A higher threshold of 30μg/L is used in the presence of infection or inflammation. Iron deficiency anemia, with typical low mean corpuscular volume and mean corpuscular hemoglobin, is only present at the end stage of iron deficiency. Other diagnostic tests for iron deficiency including iron parameters (low serum iron, increased total iron-binding capacity, low transferrin saturation) and erythrocyte traits (low mean corpuscular volume, increased zinc protoporphyrin) provide little additional diagnostic value over SF. In children, serum soluble transferrin receptor (sTfR) has been reported to be a sensitive indicator of iron deficiency and is relatively unaffected by inflammation. On the other hand, sTfR is directly related to extent of erythroid activity and not commonly used in clinical practice. In population surveys, approaches based on combinations of markers have been explored to improve the specificity and sensitivity of diagnostic. In addition to Hb value determination, a combination of parameters (among transferrin saturation, zinc protoporphyrin, mean corpuscular volume or serum ferritin) was generally used to assess iron deficiency. More recently sTfR/ ferritin index were evaluated, sTfR in conjunction with SF allowing to better distinguishing iron deficiency from inflammatory anemia. Also, hepcidin measurements appeared an interesting marker for diagnosing iron deficiency and identifying individuals in need of iron supplementation in populations where inflammatory or infectious diseases are frequently encountered. Reticulocyte Hb content (CHr) determination is an early parameter of iron deficiency erythropoiesis. CHr can be measured with several automated hematology analyzers and so, used for individual's iron status assessment. In addition to Hb concentration determination, individual's iron status is commonly assessed in the pediatric clinical practice by the SF measurement accompanied by the determination of C-reactive protein for detection of a simultaneous acute infection and/or inflammation.

Anemia of Inflammation during Human Pregnancy Does Not Affect Newborn Iron Endowment

Background

To our knowledge, no studies have addressed whether maternal anemia of inflammation (AI) affects newborn iron status, and few have addressed risk factors for specific etiologies of maternal anemia.

Objectives

The study aims were to evaluate 1) the contribution of AI and iron deficiency anemia (IDA) to newborn iron endowment, 2) hepcidin as a biomarker to distinguish AI from IDA among pregnant women, and 3) risk factors for specific etiologies of maternal anemia.

Methods

We measured hematologic biomarkers in maternal blood at 12 and 32 wk of gestation and in cord blood from a randomized trial of praziquantel in 358 pregnant women with Schistosoma japonicum in The Philippines. IDA was defined as anemia with serum ferritin <30 ng/mL and non-IDA (NIDA), largely due to AI, as anemia with ferritin ≥30 ng/mL. We identified cutoffs for biomarkers to distinguish IDA from NIDA by using area under the curve (AUC) analyses and examined the impact of different causes of anemia on newborn iron status (primary outcome) by using multivariate regression modeling.

Results

Of the 358 mothers, 38% (n = 136) had IDA and 9% (n = 32) had NIDA at 32 wk of gestation. At 32 wk of gestation, serum hepcidin performed better than soluble transferrin receptor (sTfR) in identifying women with NIDA compared with the rest of the cohort (AUCs: 0.75 and 0.70, respectively) and in identifying women with NIDA among women with anemia (0.73 and 0.72, respectively). The cutoff that optimally distinguished women with NIDA from women with IDA in our cohort was 6.1 µg/L. Maternal IDA, but not NIDA, was associated with significantly lower newborn ferritin (114.4 ng/mL compared with 148.4 µg/L; P = 0.042).

Conclusions

Hepcidin performed better than sTfR in identifying pregnant women with NIDA, but its cost may limit its use. Maternal IDA, but not NIDA, is associated with decreased newborn iron stores, emphasizing the need to identify this cause and provide iron therapy. This trial was registered at www.clinicaltrials.gov as NCT00486863.

Value of Soluble Transferrin Receptors and sTfR/log Ferritin in the Diagnosis of Iron Deficiency Accompanied by Acute Infection

There are many causes of anemia; the most common of these are acute and chronic infections, iron deficiency, or both. Identifying the cause is a very important step in management of anemia. So, we evaluated the usefulness of soluble transferrin receptor (sTfR) and of the sTfR/log ferritin in the diagnosis of iron deficiency anemia accompanied by acute infection. This study was conducted on 131 children aged 2-11 years old from those who attended the pediatric outpatient clinics in Menoufia university hospital. Hematological indices, iron balance and sTfR were evaluated and the sTfR/log F was calculated for each examined child. From the examined children four groups were distinguished: Group I (control): included 34 healthy children with normal iron status (66.7% males, age 4.2 ± 1.2). Group II (IDA): included 38 children diagnosed as iron deficiency anemia (47.4% males, age 4.9 ± 1.6). Group III (IDA + infection): included 26 children with infectious disease (upper respiratory tract infection, otitis media, pneumonia, stomatitis, and urinary tract infection) and anemia meeting criteria of IDA (50% males, age 4.2 ± 0.7). Group IV (anemia + infection): included 33 children with infectious anemia without iron deficiency (56.2% males, age 5.06 ± 1.4). It was proved that sTfR and sTfR/log Ferritin were significantly higher in children with anemia due to iron deficiency, and in those with infection + iron deficiency, versus those with infectious anemia or in healthy children. The use of sTfR and sTfR/log ferritin improves the diagnosis of IDA in pediatric patients, especially in the presence of coexisting acute infection.

A Review of Cutoffs for Nutritional Biomarkers

The nutritional status of an individual or population needs to be assessed through valid and reliable biomarkers. Cutoffs generally have an underlying relation to health status and are one of the important quantitative criteria against which biomarker outputs are compared. For this reason, cutoffs are integral for surveys, surveillance, screening, interventions, monitoring, and evaluation. Despite their importance, nutritional biomarker cutoffs have not been adequately addressed in the literature. Furthermore, the field has not reached a consensus on which cutoff to use for each biomarker, and different cutoffs are often used for the same biomarkers in published studies. This review provides a comprehensive overview of cutoffs related to nutritional biomarkers and highlights some of the high-priority research gaps and challenges of using micronutrient case studies.

Depleted iron stores and iron deficiency anemia associated with reduced ferritin and hepcidin and elevated soluble transferrin receptors in a multiethnic group of preschool-age children

Iron deficiency anemia is prevalent in subgroups of the Canadian population. The objective of this study was to examine iron status and anemia in preschool-age children. Healthy children (n = 430, 2–5 years old, Montreal, Quebec, Canada) were sampled from randomly selected daycares. Anthropometry, demographics, and diet were assessed. Biochemistry included hemoglobin, ferritin, soluble transferrin receptors (sTfR), ferritin index, markers of inflammation (C-reactive protein, interleukin 6 (IL-6), and tumour necrosis factor alpha (TNFα)), and hepcidin. Iron deficiency and anemia cutoffs conformed to the World Health Organization criteria. Differences among categories were tested using mixed-model ANOVA or χ2tests. Children were 3.8 ± 1.0 years of age, with a body mass index z score of 0.48 ± 0.97, and 51% were white. Adjusted intakes of iron indicated <1% were at risk for deficiency. Hemoglobin was higher in white children, whereas ferritin was higher with greater age and female sex. Inflammatory markers and hepcidin did not vary with any demographic variable. The prevalence of iron deficiency was 16.5% (95% confidence interval (CI), 13.0–20.0). Three percent (95% CI, 1.4–4.6) of children had iron deficiency anemia and 12.8% (95% CI, 9.6–16.0) had unexplained anemia. Children with iron deficiency, with and without anemia, had lower plasma ferritin and hepcidin but higher sTfR, ferritin index, and IL-6, whereas those with unexplained anemia had elevated TNFα. We conclude that iron deficiency anemia is not very common in young children in Montreal. While iron deficiency without anemia is more common than iron deficiency with anemia, the correspondingly reduced circulating hepcidin would have enabled heightened absorption of dietary iron in support of erythropoiesis.

Optical sensor: a promising strategy for environmental and biomedical monitoring of ionic species

In this review, we cover the recent developments in fluorogenic and chromogenic sensors for Cu²⁺, Fe²⁺/Fe³⁺, Zn²⁺and Hg²⁺.

The value of Ret-Hb and sTfR in the diagnosis of iron depletion in healthy, young children

OBJECTIVES

Reticulocyte hemoglobin (Ret-Hb) content and soluble transferrin receptor (sTfR) are described as promising biomarkers in the analysis of iron status. However, the value of Ret-Hb and sTfR in the early detection of iron depletion, as frequently observed in children in high-income countries, is unclear. We hypothesized that young children to iron depletion, using the WHO cutoff of ferritin <12 μg/l, would have lower Ret-Hb and higher sTfR concentrations compared to children with a ferritin ⩾level 12 μg/l.

SUBJECTS/METHODS

In this cross-sectional study, we analyzed mean concentrations of Ret-Hb and sTfR in 351 healthy children aged 0.5-3 years in a high-income country. The Student's t-test was used to compare Ret-Hb and sTfR concentrations between groups.

RESULTS

We showed that concentrations of Ret-Hb and sTfR are similar in children with and without iron depletion. A decrease in Ret-Hb concentration was present only when ferritin concentrations were <8 μg/l. sTfR concentrations were similar in children with ferritin concentrations <6 μg/l and ⩾12 μg/l.

CONCLUSIONS

Our results showed that the discriminative value of Ret-Hb and sTfR for the detection of iron depletion is limited. Our findings suggest that ferritin is the most useful biomarker in the screening of iron depletion in healthy children in high-income countries. However, ideally, reference ranges of iron status biomarkers should be based on studies showing that children with concentrations outside reference ranges have poor neurodevelopmental outcomes.

Comparison of two doses of elemental iron in the treatment of latent iron deficiency: efficacy, side effects and blinding capabilities

Adherence to iron supplementation can be compromised due to side effects, and these limit blinding in studies of iron deficiency. No studies have reported an efficacious iron dose that allows participants to remain blinded. This pilot study aimed to determine a ferrous sulfate dose that improves iron stores, while minimising side effects and enabling blinding. A double-blinded RCT was conducted in 32 women (18-35 years): 24 with latent iron deficiency (serum ferritin < 20 µg/L) and 8 iron sufficient controls. Participants with latent iron deficiency were randomised to 60 mg or 80 mg elemental iron or to placebo, for 16 weeks. The iron sufficient control group took placebo. Treatment groups (60 mg n = 7 and 80 mg n = 6) had significantly higher ferritin change scores than placebo groups (iron deficient n = 5 and iron sufficient n = 6), F(1, 23) = 8.46, p ≤ 0.01. Of the 24 who completed the trial, 10 participants (77%) on iron reported side effects, compared with 5 (45%) on placebo, but there were no differences in side effects (p = 0.29), or compliance (p = 0.60) between iron groups. Nine (69%) participants on iron, and 11 (56%) on placebo correctly guessed their treatment allocation. Both iron doses were equally effective in normalising ferritin levels. Although reported side-effects were similar for both groups, a majority of participants correctly guessed their treatment group.

Assessing chaperone for Zn, Cu-superoxide dismutase as an indicator of copper deficiency in malnourished children

It is not clear how frequent is copper deficiency in humans. Current copper markers are not sensitive enough to detect early copper deficiency and new markers are needed. CCS is a candidate to become a copper biomarker.

OBJECTIVE

Measuring CCS mRNA relative expression in malnourished children and compare results (a) with those of the same children after nutritional recovery and (b) with well-nourished children.

METHOD

On admission to the protocol and after 15 day nutritional treatment, severely (G1=18) and moderately (G2=10) malnourished children were compared with well-nourished healthy controls (G3=15), measuring anthropometric indicators, blood biochemistry, Cu, Fe and Zn serum concentrations, ceruloplasmin, C Reactive protein and mRNA abundance of CCS, SOD and MT2 in peripheral mononuclear cells.

RESULT

In malnourished groups, mean serum copper concentration was below the cut-off on admission to hospital and increased after 15 days (t-test, p<0.01). On admission to protocol, CCS mRNA abundance in G1 and G2 was higher than in G3 (one way ANOVA, p<0.001). After 15 days, CCS expression decreased as expected (t-test, p<0.001). Initial SOD mRNA relative abundance was higher in study groups than controls and also between G1 and G2 (One way ANOVA, both p<0.01); after 15 days, G1 and G2 were not different (t-test, NS). MT2A abundance of transcripts did not follow a clear change pattern.

CONCLUSION

CCS mRNA abundance responded as expected, being higher in malnourished children than in controls; nutritional recovery in these latter resulted in decreasing expression of the chaperone, supporting the hypothesis that CCS may be a copper biomarker.

Impact of inflammation on the biomarkers of iron status in a cross-sectional survey of Lao women and children

Anaemia is prevalent in South East Asia and Fe deficiency (ID) is considered to be the main cause, but the role of subclinical inflammation in the aetiology is uncertain. In the present study, we determined the influence of inflammation on the biomarkers of Fe status in women and children, and herein, we discuss the proportion of anaemia associated with ID. As part of the 2006 Lao People's Democratic Republic (The Lao PDR) National Nutrition Survey, blood collected from 482 young children and 816 non-pregnant women was analysed. Plasma ferritin, transferrin receptor (sTfR), Hb, C-reactive protein (CRP) and α-1-acid glycoprotein (AGP) concentrations were measured. ID was assessed using ferritin concentrations ( < 12 (children) or < 15 (adults) μg/l), sTfR concentrations (>8.3 mg/l) and body Fe stores (BIS < 0). Elevated CRP (>5 mg/l) and/or AGP (>1 g/l) concentrations were used to categorise inflammation status in order to correct the Fe biomarkers for inflammation. Inflammation was present in 14% of adults and 43% of children. Anaemia was present in 37.6% of both women (Hb concentrations < 120 g/l) and children (Hb concentrations < 110 g/l). Correcting ferritin concentrations for inflammation increased the prevalence of ID from 24.3 to 26% for women and from 18 to 21% for children (P< 0.001 for both). Ferritin concentrations were more helpful in detecting ID than sTfR concentrations or BIS, but regression analysis found that sTfr concentrations explained more of the variance in Hb concentrations in both women (20%) and children (17%) than ferritin concentrations (5 and 1.4%, respectively). Nevertheless, the total variance in Hb concentrations explained was only 26 and 18 % in women and children, respectively, and other factors may be more important than ID in contributing to anaemia in The Lao PDR.

Psychosocial stimulation benefits development in nonanemic children but not in anemic, iron-deficient children

Young children with iron deficiency anemia (IDA) usually have poor development, but there is limited information on their response to psychosocial intervention. We aimed to compare the effects of psychosocial stimulation on the development of children with IDA and children who were neither anemic nor iron deficient (NANI). NANI (n = 209) and IDA (n = 225) children, aged 6-24 mo, from 30 Bangladeshi villages were enrolled in the study. The villages were then randomized to stimulation or control, and all children with IDA received 30 mg iron daily for 6 mo. Stimulation comprised 9 mo weekly play sessions at home. We assessed children's development at baseline and after 9 mo by using the Psychomotor Development Index (PDI) and the Mental Development Index (MDI) of the Bayley Scales of Infant Development-II, and rated their behavior during the test. When we controlled for socioeconomic background, the IDA and NANI groups did not differ in their Bayley scores and behavior at baseline. After 9 mo, the IDA group had improved in iron status compared with baseline but had lower PDI scores and were less responsive to the examiner than the NANI group. Random-effects multilevel regressions of the final Bayley scores of the IDA and NANI groups showed that stimulation improved children's MDI [B ± SE = 5.7 ± 1.9 (95% CI: 2.0, 9.4), P = 0.003], and the interaction between iron status and stimulation showed a suggestive trend (P = 0.10), indicating that children with IDA and NANI responded differently to stimulation, with the NANI group improving more than the IDA group. In addition to iron treatment, children with IDA may require more intense or longer interventions than NANI children.

Estimating the prevalence of iron deficiency in the first two years of life: technical and measurement issues

National-level data on iron deficiency is not available for most countries and many rely on the prevalence of anemia as a proxy estimate, assuming that approximately 50% of anemia cases are caused by iron deficiency. Anemia, however, has multiple causal factors and the risk attributable to any one cause will depend on its relative importance in a population in relation to other causes. The present review summarizes current estimates on the prevalence of iron deficiency and anemia in children younger than 2 years and evaluates the strengths and weaknesses of currently available indicators of iron deficiency in children. Anemia prevalence is insufficient to estimate the prevalence of iron deficiency in children younger than 2 years. The methods widely used to assess iron deficiency at the population level rely on venous blood samples and are complicated and costly to implement.

Complementary foods fortified with micronutrients prevent iron deficiency and anemia in Vietnamese infants

To investigate whether an intervention including micronutrient-fortified complementary foods can improve iron status, we conducted a randomized controlled trial in 5-mo-old Vietnamese infants (n = 246). Villages (n = 29) were randomly divided into those receiving instant flour (FF) or a food complement (FC) both fortified with micronutrients or nothing [control (C)]. FF and FC infants received daily for 6 mo at least 2 meals of fortified complementary foods. Micronutrient status was assessed by measurement of hemoglobin (Hb) and plasma ferritin (PF), transferrin receptor, zinc, and retinol. Final Hb (mean ± SD) was higher in the FF (112.5 ± 8.0 g/L) and FC (114.0 ± 7.0 g/L) groups compared with C (109.0 ± 8.0 g/L; P = 0.006). PF (geometric mean [95% CI]) was also higher in FF (19.8 μg/L [17.5-22.3]) and FC (20.8 μg/L [18.3-23.6]) compared with C (11.1 μg/L [9.8-12.5]; P < 0.0001). Anemia prevalence decreased more in the FC group (-43.6%) compared with C (-10.3%; P = 0.006). The change in prevalence of PF < 12 μg/L was different in the FF (-16.4%) and FC (-6.7%) groups compared with C (+30.4%; P < 0.01). Endpoint prevalence of iron deficiency (ID) and ID anemia (IDA) were lower in the FF (13.4 and 6.7%, respectively) and FC (15.2 and 3.8%) groups compared with C (57.5 and 37.5%) (P < 0.0001). Retinol and zinc concentrations did not differ among groups, but endpoint prevalence of zinc deficiency was lower in FF infants (36.1%) than in C infants (52.9%; P = 0.04). Micronutrient-fortified complementary foods significantly improved iron status and decreased the prevalence of anemia, ID, and IDA in Vietnamese infants and can be an important tool to reduce ID in infancy in developing countries.

Development of nutritional iron deficiency in growing male rats: haematological parameters, iron bioavailability and oxidative defence

Despite Fe deficiency having been widely studied, the sequence of events in its development still remains unclear. The aim of the present study was to elucidate the effects of nutritional Fe-deficiency development on haematological parameters, Fe bioavailability and the enzymes involved in oxidative defence in recently weaned male Wistar albino rats. Control (C) and Fe-deficient (ID) groups were fed the AIN-93 G diet with a normal Fe level (45 mg/kg diet) or with a low Fe level (5 mg/kg diet), respectively, for 20, 30 or 40 d. At day 20 serum Fe, serum ferritin and the saturation of transferrin decreased drastically, decreasing further in the course of Fe-deficiency development for the saturation of transferrin. The development of Fe deficiency did not affect plasma thiobarbituric acid-reactive substance production, or catalase (CAT) and glutathione peroxidase (GPx) activities in erythrocyte cytosol. Fe deficiency diminished hepatic Fe content and CAT and GPx activities in hepatic cytosol only at day the 20. However, in spite of the minor Fe deposits in the brain of ID rats, the CAT and GPx activities in the brain cytosolic fraction did not differ in any of the studied periods v. control rats. These results show that brain is a tissue that does not seem to depend on Fe levels for the maintenance of antioxidant defence mechanisms in the course of nutritional Fe deficiency.

Evaluation of iron deficiency as a nutritional adaptation to infectious disease: an evolutionary medicine perspective

An evolutionary perspective suggests that iron deficiency may have opposing effects on infectious disease risk, decreasing susceptibility by restricting iron availability to pathogens, and increasing susceptibility by compromising cellular immunocompetence. In some environments, the trade-off between these effects may result in optimal iron intake that is inadequate to fully meet body iron needs. Thus, it has been suggested that moderate iron deficiency may protect against acute infection, and may represent a nutritional adaptation to endemic infectious disease stress. To test this assertion, we examined the association between infection, reflected by C-reactive protein, a biomarker of inflammation, and iron status, reflected by transferrin receptor (TfR) and zinc protoporphyrin to heme ratio (ZPP:H), among school-age Kenyan children, and evaluated the hypothesis that moderate iron deficiency is associated with lower odds of infectious disease. TfR > 5.0 mg/l, with sensitivity and specificity for iron deficiency (ZPP:H > 80 micromol/mol) of 0.807 and 0.815, was selected as the TfR definition of iron deficiency. Controlling for age and triceps skinfold thickness (TSF), the odds ratio (OR) for acute viral or bacterial infection associated with iron deficiency (compared to normal/replete) was 0.50 (P = 0.11). Controlling for age and TSF, the OR for infection associated with an unequivocally iron replete state (compared to all others) was 2.9 (P = 0.01). We conclude that iron deficiency may protect against acute infection in children.

Methods to assess iron and iodine status

Four methods are recommended for assessment of iodine nutrition: urinary iodine concentration, the goitre rate, and blood concentrations of thyroid stimulating hormone and thyroglobulin. These indicators are complementary, in that urinary iodine is a sensitive indicator of recent iodine intake (days) and thyroglobulin shows an intermediate response (weeks to months), whereas changes in the goitre rate reflect long-term iodine nutrition (months to years). Spot urinary iodine concentrations are highly variable from day-to-day and should not be used to classify iodine status of individuals. International reference criteria for thyroid volume in children have recently been published and can be used for identifying even small goitres using thyroid ultrasound. Recent development of a dried blood spot thyroglobulin assay makes sample collection practical even in remote areas. Thyroid stimulating hormone is a useful indicator of iodine nutrition in the newborn, but not in other age groups. For assessing iron status, haemoglobin measurement alone has low specificity and sensitivity. Serum ferritin remains the best indicator of iron stores in the absence of inflammation. Measures of iron-deficient erythropoiesis include transferrin iron saturation and erythrocyte zinc protoporphyrin, but these often do not distinguish anaemia due to iron deficiency from the anaemia of chronic disease. The serum transferrin receptor is useful in this setting, but the assay requires standardization. In the absence of inflammation, a sensitive method to assess iron status is to combine the use of serum ferritin as a measure of iron stores and the serum transferrin receptor as a measure of tissue iron deficiency.

Effect of daily or weekly multiple-micronutrient and iron foodlike tablets on body iron stores of Indonesian infants aged 6-12 mo: a double-blind, randomized, placebo-controlled trial

BACKGROUND

There is still uncertainty about the best procedure to alleviate iron deficiency. Additionally more reliable methods are needed to assess the effect of iron intervention.

OBJECTIVE

We examined the efficacy of daily iron (10 mg), daily and weekly multiple-micronutrient supplementation (10 and 20 mg Fe, respectively) in improving body iron stores of Indonesian infants.

DESIGN

Infants aged 6-12 mo were randomly allocated to 1 of 4 groups: daily multiple-micronutrients (DMM) foodlike tablets (foodLETs), weekly multiple-micronutrient (WMM) foodLETs, daily iron (DI) foodLETs, or daily placebo. Hemoglobin, ferritin, transferrin receptors, and C-reactive protein data were obtained at baseline and 23 wk.

RESULTS

Body iron estimated from the ratio of transferrin receptors to ferritin was analyzed for 244 infants. At baseline, mean iron stores (0.5 +/- 4.1 mg/kg) did not differ among the groups, and 45.5% infants had deficits in tissue iron (body iron < 0). At week 23, the group DI had the highest increment in mean body iron (4.0 mg/kg), followed by the DMM group (2.3 mg/kg; P < 0.001 for both). The iron stores in the WMM group did not change, whereas the mean body iron declined in the daily placebo group (-2.2 mg/kg; P < 0.001). Compared with the daily placebo group, the DMM group gained 4.55 mg Fe/kg, the DI group gained 6.23 mg Fe/kg (both P < 0.001), and the WMM group gained 2.54 mg Fe/kg (P = 0.001).

CONCLUSIONS

When compliance can be ensured, DI and DMM foodLETs are efficacious in improving and WMM is efficacious in maintaining iron stores among Indonesian infants.

Serum transferrin receptor, ferritin, and reticulocyte maturity indices during the first year of life in 'large' preterm infants

BACKGROUND

Preterm infants are at risk of developing iron deficiency; among the iron status and hemopoiesis indices the serum transferrin receptor (sTfr) has been shown to be a useful indicator in assessing iron status, while immature reticulocyte production is regarded as an estimator of erythropoiesis.

OBJECTIVE

To investigate age-related changes in iron status infants born 'moderately' preterm, with a gestational age (GA) of 32-36 wk, and identify associations between sTfr and other hematological and biochemical iron indices.

DESIGN

Hospital-based prospective, longitudinal study in preterm infants.

METHODS

Iron and erythropoiesis parameters were evaluated in 181 formula-fed preterm infants at 2 and 6 wk and 3, 6, 9, and 12 months chronological age. Hemoglobulin (Hb), hematocrit (Hct), mean corpuscular volume (MCV), reticulocytes, serum iron (sFe), serum ferritin (sFer), sTfr, and reticulocyte subpopulations were measured.

RESULTS

A total of 756 measurements were performed. After an initial decline, Hb rose from month 3 to 12 of life. SFe and sFer and immature reticulocyte count decreased from the second week to the third month and remained stable thereafter. STfr was lower up to 6 wk and stable from month 3 to 12. Iron deficiency anemia (IDA) was found in 5.5% of infants. In 76 measurements sFer was <12 microg/L, implying storage iron deficiency (SID). A negative correlation was observed between sTfr and other indices of iron status such as Hb, Hct, MCV, sFe, and sFer. Infants with sFer <12 microg/L had lower sTfr than those with sFer >12 microg/L. Reticulocyte production was positively associated with STfr, but this association was dependent on the chronological age of the infant.

CONCLUSION

Iron depletion is common in formula-fed preterm (32-36 wk GA) infants between month 3 and 12 of life. STfr appears to be an indicator of iron status in preterm infants during the first year of life.

Soluble transferrin receptor as an indicator of iron deficiency in HIV-infected infants

BACKGROUND

Iron deficiency is common in human immunodeficiency virus (HIV)-infected infants in sub-Saharan Africa. It is not known whether soluble transferrin receptor (sTfR) is a good indicator of iron deficiency in infants with HIV.

METHODS

We evaluated sTfR as an indicator of iron deficiency in 134 HIV-infected 9-month-old infants in Kampala, Uganda. Ferritin <12 microg/L and microcytic, hypochromic anaemia were used as indicators of iron deficiency, respectively. The presence of inflammation was indicated by C-reactive protein >5 mg/L or alpha1-acid glycoprotein >1 g/L.

RESULTS

Receiver operator characteristic curves showed that the area under the curve was 0.67 when sTfR receptor was compared with low ferritin and 0.71 when sTfR was compared with microcytic, hypochromic anaemia. The appropriate calculated cut-offs of sTfR >3.74 microg/mL (43.98 nmol/L) and >3.53 microg/mL (41.55 nmol/L) show adequate specificities of 60% and sensitivities of 63% and 69% for low ferritin and microcytic, hypochromic anaemia, respectively. C-reactive protein and alpha 1-acid glycoprotein were strongly correlated with serum ferritin (r=0.371 and r=0.458, respectively, both p<0.0001) but were not correlated with sTfR (r=0.009 and r= -0.003, respectively, both p=0.9). In all, 78.6% of infants had alpha l-acid glycoprotein >1 g/L and 54.7% had C-reactive protein >5 g/L.

CONCLUSIONS

Soluble TfR appears to be an adequate indicator of iron deficiency in HIV-infected infants.

Interação entre vitamina A e ferro em diferentes grupos populacionais

A interação entre ferro e vitamina A tem sido alvo de pesquisas científicas, visto que existem questões ainda pouco esclarecidas. Através de um levantamento bibliográfico, mediante consulta à base de dados Medline da National Library of Medicine, Estados Unidos da America, foram selecionadas publicações que tratavam sobre a interação entre ferro e vitamina A em seres humanos, a partir da década de 80 até o ano de 2003. As palavras chave utilizadas no levantamento bibliográfico foram "ferro", "vitamina A" e "anemia" e seus correspondentes em língua inglesa. Os resultados indicam que existe correlação entre os indicadores do estado nutricional de vitamina A e ferro em crianças, adolescentes e gestantes e que a fortificação e suplementação com vitamina A têm efeito favorável no metabolismo do ferro nesses grupos. Entretanto, ainda são necessários mais estudos para se conseguir estabelecer quais as doses e o período necessário de suplementação de vitamina A para beneficiar significantemente o estado nutricional de ferro. Os mecanismos que explicam a associação entre vitamina A e ferro ainda são desconhecidos, entretanto alguns autores atribuem essa interação ao fato de a vitamina A beneficiar a eritropoese, prevenir infecções ou melhorar a absorção de ferro.

On risks and benefits of iron supplementation recommendations for iron intake revisited

Iron is an essential trace element with a high prevalence of deficiency in infants and in women of reproductive age from developing countries. Iron deficiency is frequently associated with anaemia and, thus, with reduced working capacity and impaired intellectual development. Moreover, the risk for premature delivery, stillbirth and impaired host-defence is increased in iron deficiency. Iron-absorption and -distribution are homeostatically regulated to reduce the risk for deficiency and overload. These mechanisms interact, in part, with the mechanisms of oxidative stress and inflammation and with iron availability to pathogens. In the plasma, fractions of iron may not be bound to transferrin and are hypothesised to participate in atherogenesis. Repleted iron stores and preceding high iron intakes reduce intestinal iron absorption which, however, offers no reliable protection against oral iron overload. Recommendations for dietary iron intake at different life stages are given by the US Food and Nutrition Board (FNB), by FAO/WHO and by the EU Scientific Committee, among others. They are based, on estimates for iron-losses, iron-bioavailability from the diet, and iron-requirements for metabolism and growth. Differences in choice and interpretation of these estimates lead to different recommendations by the different panels which are discussed in detail. Assessment of iron-related risks is based on reports of adverse health effects which were used in the attempts to derive an upper safe level for dietary iron intake. Iron-related harm can be due to direct intestinal damage, to oxidative stress, or to stimulated growth of pathogens. Unfortunately, it is problematic to derive a reproducible cause-effect and dose-response relationship for adverse health effects that suggest a relationship to iron-intake, be they based on mechanistic or epidemiological observations. Corresponding data and interpretations are discussed for the intestinal lumen, the vascular system and for the intracellular and interstitial space, considering interference of the mechanisms of iron homoeostasis as a likely explanation for differences in epidemiological observations.

Serum transferrin receptor in children: usefulness for determinating the nature of anemia in infection

OBJECTIVES

To know the variations of serum transferrin receptor (sTfR) and its indices depending on the status of body iron and the presence of infection in children, to evaluate their usefulness for recognizing the nature of anemia in infection, and to know the role of erythropoietic activity in these conditions.

DESIGN AND METHODS

Three hundred and sixty-eight children between 1 and 10 years were included: 206 healthy children; 60 iron deficient anemic children (IDA); 102 with anemia and infectious disease, 58 of them meeting criteria for IDA. We measured hemoglobin, red cell indices, reticulocytes, transferrin saturation, serum ferritin, erythrocyte protoporphyrin, serum erythropoietin, and sTfR. Statistic method: ANOVA test, multiple linear regression, and ROC curve.

RESULTS

sTfR, sTfR/ferritin ratio, and sTfR-logferritin index values were found to increase significantly in IDA children. These values were significantly lower in infectious anemia than iron deficiency states. Serum erythropoietin only was elevated significantly in iron deficiency states. In children without infection, mean corpuscular hemoglobin, erythrocyte protoporphirin, erythropoietin logarithm, and total-iron-binding-capacity logarithm predicted 81% of sTfR variability. sTfR and its indices showed a very high sensitivity and specificity for recognizing iron deficiency states. In children with IDA and infection sensitivity for sTfR/ferritin ratio was low (area under the curve: 0.71; 95% confidence interval: 0.64-0.88). For discriminating the nature of anemia in infection the cut-off point obtained for sTfR, sTfR/ferritin ratio, and sTfR-F index were 3, 70, and 1.8, respectively, and their sensitivity and specificity were also very high.

CONCLUSIONS

sTfR, sTfR/ferritin ratio, and sTfR-F index are useful parameters for recognizing iron deficiency and the nature of anemia in infection. In IDA+infection, sTfR/ferritin ratio should not be recommended in the diagnosis of iron deficiency. In iron deficiency, erythropoietic activity has a secondary role as predictor factor of sTfR levels.

Comparative effectiveness of zinc protoporphyrin and hemoglobin concentrations in identifying iron deficiency in a group of low-income, preschool-aged children: practical implications of recent illness

OBJECTIVE

The goal was to assess the influence of recent infection on screening tests for iron depletion (zinc protoporphyrin and hemoglobin) among low-income, preschool-aged children.

METHODS

This cross-sectional study was conducted at community sites and ambulatory care clinics in Hartford, Connecticut, and included 180 preschool-aged children. Iron depletion was defined as serum ferritin levels of < or = 15 microg/L. Recent illness was defined by parent or guardian (caretaker) report or evidence of elevated C-reactive protein concentrations. History of anemia was determined through medical records review. Sensitivity, specificity and positive predictive values of hemoglobin and zinc protoporphyrin were calculated overall and for children with and without recent illness.

RESULTS

At enrollment, more than one half of the children had a recent illness, and 57.5% had a history of anemia. More than one third had iron depletion. Serum ferritin levels were significantly higher among recently ill children. Secondary to recent illness, the positive predictive value of elevated zinc protoporphyrin, but not low hemoglobin, was reduced significantly. Zinc protoporphyrin levels of >69 micromol/mol heme identified significantly more iron-deficient children.

CONCLUSIONS

Compared with anemia, elevated zinc protoporphyrin levels identified significantly more iron-deficient children. Recently ill children were one half as likely to have low serum ferritin levels, compared with children without recent illness. The negative effect of recent illness on the positive predictive value of zinc protoporphyrin when ferritin is used to determine iron status has many practical implications.

Anemia, iron deficiency, and iron deficiency anemia in 12-36-mo-old children from low-income families

BACKGROUND

Iron deficiency (ID) is the most common nutritional deficiency in the world and remains relatively common in at-risk groups in the United States. The actual prevalence of anemia, ID, and iron deficiency anemia (IDA) in California remains unclear.

OBJECTIVE

The objective was to determine the prevalence of anemia, low iron stores, ID, and IDA in children participating in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) population, and to assess the value of using hemoglobin to predict ID.

DESIGN

This was a cross-sectional study of a convenience sample of 12-36-mo-old children from WIC clinics in 2 California counties.

RESULTS

The prevalence of anemia was 11.1% (hemoglobin <110 g/L at 12-24 mo or <111 g/L at 24-36 mo). Study- and literature-determined abnormal values for iron measures were as follows: serum ferritin <or=8.7 or <10.0 microg/L, serum transferrin receptor >or=8.4 or >10.0 microg/mL, and transferrin saturation <or=13.2% or <10.0%, respectively. The prevalences of low iron stores (low ferritin) were 24.8% and 29.0%, of ID (>or=2 abnormal iron measures) were 16.2% and 8.8%, and of IDA (ID with low hemoglobin) were 3.4% and 3.2% on the basis of study- and literature-determined cutoffs, respectively. Hemoglobin concentration was used to predict study- and literature-determined ID on the basis of receiver operating characteristic curves. The sensitivity of low hemoglobin in predicting study- and literature-determined ID was low (23.2% and 40.0%, respectively).

CONCLUSIONS

Anemia and ID were prevalent in this WIC sample, but IDA was uncommon. Low hemoglobin is a poor predictor of ID.

Soluble transferrin receptor in hemochromatosis patients during phlebotomy therapy

BACKGROUND

The monitoring of phlebotomies in hemochromatosis patients depends on iron status measured by ferritin and transferrin saturation (TS). However, in the presence of inflammation or liver injury, soluble transferrin receptor (sTfR) determination was proposed to replace ferritin for diagnosing iron deficiency (ID). The present study evaluated performances of sTfR for the prediction of iron deficiency in a large number of hemochromatosis patients under phlebotomy therapy.

METHODS

We studied 52 patients undergoing therapeutic phlebotomies and obtained 2 samples from 37 patients. Biological parameters were determined before each phlebotomy began. Performances of sTfR and TS in the diagnosis of iron deficiency were compared, according to ferritin levels under 12 microg/l.

RESULTS

Ferritin and TS were correlated with removed iron (r=0.473, p<0.005 and r=0.345, p<0.05, respectively) and sTfR was correlated with the decrease in hemoglobin levels induced by phlebotomies (r=-0.678, p<0.0001). Areas under Receiver Operating Characteristics (ROC) curves for sTfR and TS were not statistically different for prediction of iron deficiency and sensitivity/specificity of sTfR at 1.64 mg/l were 67/86%.

CONCLUSIONS

sTfR determination could be used to predict iron depletion induced by phlebotomies when ferritin is of limited interest, to avoid the appearance of anemia.

Serum transferrin receptor and zinc protoporphyrin as indicators of iron status in African children

BACKGROUND

Although transferrin receptor (TfR) and zinc protoporphyrin (ZnPP) are often used to define iron status in school-age children in developing countries, the diagnostic cutoffs for this age group are uncertain.

OBJECTIVE

The objective was to determine the sensitivity and specificity of TfR and ZnPP in predicting iron deficiency in black and white children in Africa.

DESIGN

Hemoglobin, C-reactive protein (CRP), serum ferritin (SF), TfR, and ZnPP were measured in children in Côte d'Ivoire and Morocco. We excluded children with elevated CRP and then used receiver operating characteristic (ROC) curves to evaluate TfR and ZnPP alone and in combination in screening for iron deficiency, defined as an SF concentration <15 mug/L, and iron deficiency anemia (IDA), defined as an SF concentration <15 mug/L and low hemoglobin.

RESULTS

The sample included 2814 children aged 5-15 y. The sensitivity and specificity of TfR and ZnPP were limited by considerable overlap between iron-sufficient, nonanemic children and those with IDA. On the basis of ROC curves, we identified diagnostic cutoffs for TfR and ZnPP that achieved specificities and sensitivities of approximately 60-80%. Separate cutoffs for Côte d'Ivoire and Morocco gave the best performance; the cutoffs for both TfR and ZnPP were higher in Côte d'Ivoire. Moreover, a comparison of nonanemic, iron-sufficient subjects showed that Ivorian children had significantly higher TfR and ZnPP concentrations than did Moroccan children (P < 0.01).

CONCLUSIONS

New diagnostic cutoffs for TfR and ZnPP, based on ROC curve analyses, may improve the performance of these indexes in defining iron status in children. Significant ethnic differences in TfR and ZnPP suggest that separate cutoffs may be needed for black and white children.

Anemia is a poor predictor of iron deficiency among toddlers in the United States: for heme the bell tolls

CONTEXT

Many toddlers in the United States have their hemoglobin (Hb) measured periodically. Is this worthwhile?

OBJECTIVE

To determine if the presence of anemia correctly diagnoses iron deficiency (ID) and if the absence of anemia correctly rules out ID in young children.

METHODOLOGY

An analysis of data from the US National Health and Nutrition Examination Survey III (1988-1994) was performed. Subjects were children 12 to 35 months old for whom complete blood counts and cardinal measures of iron nutrition (ferritin, transferrin saturation, and free erythrocyte protoporphyrin) were reported.

RESULTS

In the US National Health and Nutrition Examination Survey III, the prevalence of ID ranged from 6% to 18% in various subpopulations of toddlers. In the general population, the positive predictive value of Hb concentration ([Hb]) <110 g/L for ID was 29% (95% confidence interval [CI]: 20-38%), and the sensitivity was 30% (95% CI: 20-40%). Changing the diagnostic cutoff point to [Hb] <107 g/L resulted in a positive predictive value of 38% (95% CI: 24-52%) but lowered the sensitivity to 15% (95% CI: 7-22%).

CONCLUSIONS

ID remains common in the United States. In agreement with other reports, anemia in toddlers in developed countries is more likely to be due to causes other than ID. Conversely, most children with ID are not anemic. Many false-positive and false-negative results render the measurement of Hb a screening test of relatively little value. The current detection strategy needlessly treats and retests many children without ID and leaves many iron-deficient toddlers unattended.

Iron status of children with phenylketonuria undergoing nutrition therapy assessed by transferrin receptors

PURPOSE

The purpose of the study was to determine the incidence of iron deficiency in children undergoing therapy for phenylketonuria using serum transferrin receptor and ferritin concentrations.

METHODS

A 1-year study was conducted in 37 children 2 <13 years old with phenylketonuria (8 fed Periflex [Group I], 15 fed Phenex-2 Amino Acid-Modified Medical Food [Group II], and 14 fed Phenyl-Free [Group III]). Hemoglobin, hematocrit, serum transferrin receptor, and ferritin concentrations were assessed at baseline and 12 months and intakes of protein, iron, and vitamin C were evaluated at baseline and at 3-month intervals. Transferrin receptor and ferritin concentrations were analyzed for group differences by analysis of variance.

RESULTS

Mean protein, iron, and vitamin C intakes of all 3 groups of children were greater than Recommended Dietary Intakes for age. Only 2 of 60 3-day diet diaries of Group II children failed to contain 100% of Recommended Dietary Intakes for iron during study. The following number of children had iron status indices outside reference ranges at study end: 7 children, transferrin receptor/ferritin ratios; 4 children, transferrin receptors; 2 children, hematocrit; 1 child, ferritin. No correlation was found between iron intake and any index of iron status.

CONCLUSIONS

The transferrin receptor/ferritin ratio appeared to be the most sensitive index of iron deficiency in this study. Reasons for iron deficiency with greater than recommended iron intakes by children with phenylketonuria may be multiple. Early assessment and therapy of iron deficiency may improve cognitive and behavioral outcomes of children with PKU.

Preconception hemoglobin and ferritin concentrations are associated with pregnancy outcome in a prospective cohort of Chinese women

Prenatal anemia and iron deficiency are associated with adverse birth outcomes, but no previous studies have examined the relation between preconception anemia, iron deficiency, and pregnancy outcome in healthy women. We measured hemoglobin (Hb), ferritin, transferrin receptor (TfR), and vitamins B-6, B-12, and folate concentrations before pregnancy in 405 Chinese women (median time from sample collection to gestation end = 316 d). Both mild (95 </= Hb < 120 g/L) and moderate (Hb < 95 g/L) anemia were significantly associated with lower birthweight (139 and 192 g, respectively); iron-deficiency anemia alone (Hb < 120 g, ferritin < 12 microg/L, no B-vitamin deficiency) was associated with a 242-g decrease in birthweight. Both low (<12 microg/L) and high (>/=60 microg/L) ferritin were also significantly associated with lower birthweight (106 and 123 g, respectively). The risks of low birthweight (LBW) and fetal growth restriction (FGR) were significantly greater among women with moderate anemia compared with nonanemic controls [odds ratio (OR): 6.5; 95% CI: 1.6, 26.7; P = 0.009 and OR: 4.6; 95% CI: 1.5, 13.5; P = 0.006, respectively]. TfR and low ferritin were not associated with adverse birth outcome, but elevated ferritin, which could be a marker of inflammation, was associated with increased risk of LBW (OR: 2.2; 95% CI: 0.9, 5.7; P = 0.09) and FGR (OR: 2.7; 95% CI: 1.3, 5.6; P = 0.008). Preconception anemia, particularly iron-deficiency anemia, was associated with reduced infant growth and increased risk of adverse pregnancy outcome in Chinese women.

Dietary iron intake is positively associated with hemoglobin concentration during infancy but not during the second year of life

Iron status during infancy and early childhood reflects highly dynamic processes, which are affected by both internal and external factors. The regulation of iron metabolism seems to be subjected to developmental changes during infancy, although the exact nature of these changes and their implications are not fully understood. We wanted to explore the association between dietary iron intake and indicators of iron status, and to assess temporal changes in these variables. This was done by secondary analysis of data from a recently conducted dietary intervention trial in which healthy, term, well-nourished infants were randomly assigned to consume iron-fortified infant cereals with regular or low phytate content, or iron-fortified infant formula. Dietary iron intake from 6 to 8 mo and from 9 to 11 mo was associated with hemoglobin (Hb) concentration at 9 mo (r = 0.27, P < 0.001) and 12 mo (r = 0.21, P = 0.001), respectively, but iron intake from 12 to 18 mo was not associated with Hb at 18 mo. In contrast, iron intake from 6 to 11 mo was not associated with serum ferritin (S-Ft) at 9 or 12 mo, whereas iron intake from 12 to 17 mo was positively associated with S-Ft at 18 mo (r = 0.14, P = 0.032). These shifts in associations between dietary iron intake, and Hb and S-Ft, respectively, may be due to developmental changes in the channeling of dietary iron to erythropoiesis relative to storage, in the absence of iron deficiency anemia. These observations should be taken into consideration when evaluating iron nutritional status during infancy and early childhood.

Receptor sérico de transferrina en niños sanos. Valor diagnóstico en la anemia infecciosa y en la ferropénica

BACKGROUND

The serum transferrin receptor (TfR) presents certain advantages over other parameters of cellular iron status because it does not vary in acute or chronic diseases.

OBJECTIVE

To establish reference ranges of TfR in healthy children for our laboratory, to define the distribution of this variable in children with acute illness and in those with iron deficiency, and to evaluate the diagnostic yield of TfR, the transferrin-receptor/ferritin ratio (TfR/F) and the transferrin-receptor-ferritin index (TfR-F) in distinguishing ferropenic from infectious anemia.

PATIENTS AND METHODS

A descriptive, cross-sectional analysis was conducted in 132 children aged from 6 months to 16 years for a period of 18 months. The subjects were classified in three groups: healthy children, children with acute illness, and children with iron deficiency. The distribution of TfR and its diagnostic yield were evaluated.

RESULTS

Of the 132 subjects, 30 were excluded because they lacked one or more of the parameters under analysis and 19 were excluded because they showed a thalassemic trait. In the 30 healthy children, the mean TfR concentration was 1.2 mg/l (SD 0.36) and the median was 1.02 (IQR 0.7-1.7). In the 32 children with acute illness, with or without anemia, TfR values were similar to those found in healthy children (p > 0.05). TfR values were higher in children with iron deficiency (21 patients; mean TfR value: 1.67 mg/l SD 0:98) than in healthy children but this difference was not statistically significant (p 0.08). The highest TfR values were found in the group with ferropenic anemia (mean TfR value: 2.13 mg/l SD 1.14) with a statistically significant difference between healthy children (p 0.04) and those with iron deficiency without anemia (p 0.01). The TfR/F ratio showed an optimal diagnostic yield in distinguishing ferropenic from acute disease anemia. If this ratio is higher than 80.7 ferropenia can be suspected as the cause of the anemia with a global value of the test of 100 % (95 % CI: 75.91-99.42).

CONCLUSIONS

TfR could be useful in evaluating intracellular iron status in children. Acute disease does not alter TfR values and, in combination with ferritin, TfR offers an optimal diagnostical yield in distinguishing ferropenic from acute illness anemia.

Soluble transferrin receptor in Aboriginal children with a high prevalence of iron deficiency and infection

OBJECTIVES

Aboriginal children in tropical Australia have a high prevalence of both iron deficiency and acute infections, making it difficult to differentiate their relative contributions to anaemia. The aims of this study were to compare soluble transferrin receptor with ferritin in iron deficiency anaemia (IDA), and to examine how best to distinguish the effect of iron deficiency from infection on anaemia.

METHODS

We conducted a prospective study of 228 admissions to Royal Darwin Hospital in children from 6 to 60 months of age. Transferrin receptor concentrations were measured by a particle-enhanced immunoturbidimetric assay and ferritin by a microparticle enzyme immunoassay.

RESULTS

On multiple regression, the best explanatory variables for haemoglobin differences (r2=33.7%, P<0.001) were mean corpuscular volume (MCV), red cell distribution width (RDW) and C-reactive protein (CRP); whereas transferrin receptor and ferritin were not significant (P>0.4). Using > or =2 abnormal indices (MCV, RDW, blood film)+haemoglobin <110 g/l as the reference standard for IDA, transferrin receptor produced a higher area under the curve on receiver operating characteristic curve analysis than ferritin (0.79 vs. 0.64, P<0.001) or the transferrin receptor-ferritin index (0.77). On logistic regression, the effect of acute infection (CRP) on haemoglobin was significant (P<0.001) at cut-offs of 105 and 110 g/l, but not at 100 g/l when only iron deficiency indicators (MCV, RDW, blood film) were significant.

CONCLUSIONS

Transferrin receptor does not significantly improve the diagnosis of anaemia (iron deficiency vs. infection) over full blood count and CRP, but in settings with a high burden of infectious diseases and iron deficiency, it is a more reliable adjunctive measure of iron status than ferritin.

Molecular mechanisms and regulation of iron transport

Iron homeostasis is primarily maintained through regulation of its transport. This review summarizes recent discoveries in the field of iron transport that have shed light on the molecular mechanisms of dietary iron uptake, pathways for iron efflux to and between peripheral tissues, proteins implicated in organellar transport of iron (particularly the mitochondrion), and novel regulators that have been proposed to control iron assimilation. The transport of both transferrin-bound and nontransferrin-bound iron to peripheral tissues is discussed. Finally, the regulation of iron transport is also considered at the molecular level, with posttranscriptional, transcriptional, and posttranslational control mechanisms being reviewed.

Soluble transferrin receptor for the evaluation of erythropoiesis and iron status

Iron transport in the plasma is carried out by transferrin, which donates iron to cells through its interaction with a specific membrane receptor, the transferrin receptor (TfR). A soluble form of the TfR (sTfR) has been identified in animal and human serum. Soluble TfR is a truncated monomer of tissue receptor, lacking its first 100 amino acids, which circulates in the form of a complex of transferrin and its receptor. The erythroblasts rather than reticulocytes are the main source of serum sTfR. Serum sTfR levels average 5.0+/-1.0 mg/l in normal subjects but the various commercial assays give disparate values because of the lack of an international standard. The most important determinant of sTfR levels appears to be marrow erythropoietic activity which can cause variations up to 8 times below and up to 20 times above average normal values. Soluble TfR levels are decreased in situations characterized by diminished erythropoietic activity, and are increased when erythropoiesis is stimulated by hemolysis or ineffective erythropoiesis. Measurements of sTfR are very helpful to investigate the pathophysiology of anemia, quantitatively evaluating the absolute rate of erythropoiesis and the adequacy of marrow proliferative capacity for any given degree of anemia, and to monitor the erythropoietic response to various forms of therapy, in particular allowing to predict response early when changes in hemoglobin are not yet apparent. Iron status also influences sTfR levels, which are considerably elevated in iron deficiency anemia but remain normal in the anemia of inflammation, and thus may be of considerable help in the differential diagnosis of microcytic anemia. This is particularly useful to identify concomitant iron deficiency in a patient with inflammation because ferritin values are then generally normal. Elevated sTfR levels are also the characteristic feature of functional iron deficiency, a situation defined by tissue iron deficiency despite adequate iron stores. The sTfR/ferritin ratio can thus describe iron availability over a wide range of iron stores. With the exception of chronic lymphocytic leukemia (CLL) and high-grade non-Hodgkin's lymphoma and possibly hepatocellular carcinoma, sTfR levels are not increased in patients with malignancies. We conclude that soluble TfR represents a valuable quantitative assay of marrow erythropoietic activity as well as a marker of tissue iron deficiency.

Increased serum soluble transferrin receptor concentration detects subclinical iron deficiency in healthy adolescent girls

The objective of this study was to investigate whether the measurement of serum soluble transferrin receptor could detect subclinical iron deficiency in adolescent girls, and to assess the possible specificity-compromising effects of growth, menarche, and intensive physical activity. The study population consisted of 191 physically active (control) girls aged 9-15 years. Dietary iron intake was estimated at baseline, and after 6 and 12 months. Iron status of the subjects was assessed by haematological laboratory tests at 6 and 12 months. A 3-month iron and multivitamin supplementation was started after the visit at 6 months. The supplementation consistently decreased soluble transferrin receptor concentrations in subjects with initial values greater than 2.4 mg/l, which was determined by regression analysis to be the cut-off value for iron-deficient erythropoiesis. The 95% reference interval in the iron-replete subjects (0.9-2.4 mg/l) was consistent with this finding. In our population, the incidence of subclinical iron deficiency was 10%. Growth or physical activity had no effect on the iron status. This study shows that, similarly to adults, soluble transferrin receptor measurement can be used to detect subclinical iron deficiency in adolescents (competitive athletes or normal controls). We suggest that soluble transferrin receptor concentrations above 2.4 mg/l indicate clinically relevant iron deficiency in adolescents.

The diagnostic criteria for iron deficiency in infants should be reevaluated

Diagnostic criteria for iron deficiency (ID) and iron deficiency anemia (IDA) in infants are poorly defined. Our aim was to establish appropriate cut-off values for hemoglobin (Hb), plasma ferritin, erythrocyte mean cell volume (MCV), zinc protoporphyrin (ZPP) and soluble transferrin receptors (TfR) in infancy. Exclusively breast-fed infants (n = 263) in Honduras and Sweden were randomly assigned to receive iron supplementation or placebo, and blood samples were obtained at 4, 6 and 9 mo of age. Reference ranges were determined using three different approaches for defining iron-replete infants. The usefulness of several variables for predicting the Hb response to iron was evaluated. We found the following 2 SD cut-off values in iron-replete infants: Hb <105 g/L at 4-6 mo and <100 g/L at 9 mo; ZPP >75 micro mol/mol heme at 4-6 mo and >90 micro mol/mol heme at 9 mo; ferritin <20 micro g/L at 4 mo, <9 micro g/L at 6 mo and <5 micro g/L at 9 mo; and TfR >11 mg/L at 4-9 mo. The Hb response to iron was not a useful definition of IDA at 4 mo of age. Hb, MCV and ZPP at 6 mo as well as growth variables predicted the Hb response at 6-9 mo, but ferritin and TfR at 6 mo did not. We conclude that there is need for a reevaluation of the definitions of ID and IDA in infants.