Iron Status of Preadolescents Without Clinical Pallor Attending a Tertiary Care Hospital in South India- A Cross-Sectional Analytical Study

OBJECTIVES

To determine the prevalence of Iron Deficiency (ID) in children without clinical pallor using serum ferritin and the new parameters, soluble transferrin receptor (sTfR) & the ratio of sTfR/log10 serum ferritin (sTfR-F index), as suggested by WHO. Also to assess whether these new parameters could individually predict the presence of ID.

METHODS

Consecutive 230 healthy children aged 9-11 y without clinical pallor underwent estimation of Hemoglobin (Hb), C-Reactive Protein (CRP), serum ferritin, sTfR, and sTfR-F index levels in their blood. The abilities of the sTfR and sTfR-F index in predicting ID were determined by comparing with the gold standard (normal CRP and less serum ferritin), plotting Receiver-operating characteristic (ROC) curve, and noting the area under the curve (AUC).

RESULTS

The blood reports of 114 boys and 106 girls (total = 220) were available for analysis. Overall, 57 (31 girls, 26 boys) children had ID; among children with low CRP, 45 had ID, as suggested by low serum ferritin levels. Among children with high CRP, 12 had evidence of ID as evidenced by elevated sTfR and/or sTfR-F index. The positive predictive values of both sTfR and sTfR-F were low (32.9% and 35.9%, respectively) than the negative predictive values (85.6% and 95.3%, respectively).

CONCLUSIONS

The proportion of children identified to have ID using serum ferritin, sTfR, and sTfR-index was 25.9%. sTfR and/or sTfR-F index are unlikely to be ideal individual predictors of ID.

Associations of a metal mixture with iron status in U.S. adolescents: Evidence from the National Health and Nutrition Examination Survey

Iron is needed for normal development in adolescence. Exposure to individual environmental metals (e.g., lead) has been associated with altered iron status in adolescence, but little is known about the cumulative associations of multiple metals with Fe status. We used data from the 2017-2018 National Health and Nutrition Examination Survey (NHANES) to examine associations between a metal mixture (lead, manganese, cadmium, selenium) and iron status in 588 U.S. adolescents (12-17 years). We estimated cumulative and interactive associations of the metal mixture with five iron status metrics using Bayesian Kernel Machine Regression (BKMR). Higher concentrations of manganese and cadmium were associated with lower log-transformed ferritin concentrations. Interactions were observed between manganese, cadmium, and lead for ferritin and the transferrin receptor, where iron status tended to be worse at higher concentrations of all metals. These results may reflect competition between environmental metals and iron for cellular uptake. Mixed metal exposures may alter normal iron function, which has implications for adolescent development.

Prevalence and Associated Factors of Iron Deficiency and Iron Deficiency Anemia Among Under-5 Children: A Systematic Review and Meta-Analysis

Background. Iron deficiency anemia is a common health problem that affects children under the age of five. Children’s cognitive performance is impaired by iron deficiency, which impacts their psychomotor development. Therefore, the aim of this study was to determine the global prevalence and associated factors of iron deficiency and iron deficiency anemia among under-5 children. Methods. Relevant publications published till March 30, 2021 were identified in databases such as Medline/PubMed, Science Direct, Popline, EMBASE, African Journals Online, Scopus, and Google Scholar. The STATA version 11 software was utilized for the analysis. To determine the level of heterogeneity, I² test statistics were used. To detect publication bias, funnel plots analysis and the Egger weighted regression test were used. Results. The global pooled prevalence of iron deficiency anemia and iron deficiency was 16.42% (95% CI: 10.82, 22.01) and 17.95% (95% CI: 13.49, 22.41), respectively. Age less than 2 years (OR = 1.26; 95% CI: 1.14, 1.38) and living in a large family size (OR = 1.38; 95% CI: 1.18, 1.58) were associated with iron deficiency anemia. Children born from anemic mother, low birth weight, and do not drink iron fortified milk (OR = 1.20; 95% CI: 1.05, 1.36), (OR = 1.15; 95% CI: 1.01, 1.36) and (OR = 1.28; 95% CI: 1.10, 1.46), respectively were associated factors of iron deficiency in under-5 children. Conclusion. The prevalence of iron deficiency anemia and iron deficiency was significant across the globe, particularly in Asia and Africa. Therefore, regular screening and treatment of iron deficiency and iron deficiency anemia are required especially in high-risk children to reduce their complication.

PROSPERO registration number: CRD42021267060

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.

The usefulness of reticulocyte haemoglobin content, serum transferrin receptor and the sTfR-ferritin index to identify iron deficiency in healthy children aged 1-16 years

This cross-sectional study, conducted on a population-based representative sample, evaluates the usefulness of reticulocyte haemoglobin content (CHr), serum transferrin receptor (sTfR) and sTfR/log ferritin (sTfR-F index) to recognise iron deficiency (ID) without anaemia, provides specific cut-off points for age and gender, and proposes a new definition of ID. A total of 1239 healthy children and adolescents aged 1-16 years were included. Complete blood count, iron biomarkers, erythropoietin, C-reactive protein, CHr, sTfR, and sTfR-F index were determined. ROC curves were obtained and sensitivity, specificity, predictive values, likelihood ratios, and accuracy for each specific cut-off points were calculated. Seventy-three had ID without anaemia. Area under the curve for sTfR-F index, sTfR and CHr were 0.97 (CI95% 0.95-0.99), 0.87 (CI95% 0.82-0.92) and 0.68 (CI95% 0.61-0.74), respectively. The following cut-off points defined ID: sTfR-F Index > 1.5 (1-5 years and 12-16 years boys) and > 1.4 (6-11 years and 12-16 years girls); sTfR (mg/L) > 1.9 (1-5 years), > 1.8 (6-11 years), > 1.75 (12-16 years girls) and > 1.95 (12-16 years boys); and CHr (pg) < 27 (1-5 years) and < 28.5 (6-16 years).Conclusions: CHr, sTfR and the sTfR-F index are useful parameters to discriminate ID without anaemia in children and adolescents, and specific cut-off values have been established. The combination of these new markers offers an alternative definition of ID with suitable discriminatory power. What is Known: • In adults, reticulocyte haemoglobin content (CHr), serum transferrin receptor (sTfR) and sTfR/log ferritin index (sTfR-F index) have been evaluated and recognised as reliable indicators of iron deficiency (ID). • Clinical manifestations of ID may be present in stages prior to anaemia, and the diagnosis of ID without anaemia continues to pose problems. What is New: • CHr, sTfR and the sTfR-F index are useful parameters in diagnosis of ID in childhood and adolescence when anaemia is not present. • We propose a new strategy for the diagnosis of ID in childhood and adolescence, based on the combination of these measures, which offer greater discriminatory power than the classical parameters.

Sickle Cell and α+-Thalassemia Traits Influence the Association between Ferritin and Hepcidin in Rural Kenyan Children Aged 14-26 Months

Background

The relation between subclinical hemoglobinopathies and concentrations of the iron-regulatory hormone hepcidin is not well characterized.

Objective

We investigated the relation of hepcidin concentration with hemoglobinopathies among young children in Kenya.

Methods

We quantified serum hepcidin and ferritin in 435 Kenyan children aged 14-20 mo in a subsample of the Water, Sanitation, and Handwashing (WASH) Benefits Trial. Blood samples were genotyped for α+-thalassemia and for sickle cell disorder. Hepcidin was compared across sickle cell and α+-thalassemia genotypes separately by using generalized linear models, and children who were normozygous for both conditions were also compared with those who had either of these conditions. In the association between hepcidin and ferritin, we assessed effect modification by genotype.

Results

In this population, we found that 16.2% had sickle cell trait and 0.2% had sickle cell disorder, whereas 40.0% were heterozygous for α+-thalassemia and 8.2% were homozygous. Hepcidin concentration did not differ by genotype, but effect modification was found by genotype in the association between hepcidin and ferritin (P < 0.1). Among normozygous sickle cell children (HbAA), there was an association between hepcidin and ferritin (β = 0.92; 95% CI: 0.72, 1.10). However, among those with sickle cell trait (HbAS), the association was no longer significant (β = 0.31; 95% CI: -0.04, 0.66). Similarly, among children who were normozygous (αα/αα) or heterozygous (-α/αα) for α+-thalassemia, hepcidin and ferritin were significantly associated [β = 0.94 (95% CI: 0.68, 1.20) and β = 0.77 (95% CI: 0.51, 1.03), respectively]; however, in children who were homozygous for α+-thalassemia (-α/-α), there was no longer a significant association (β = 0.45; 95% CI: -0.10, 1.00).

Conclusion

Hepcidin was not associated with hemoglobin genotype, but there may be a difference in the way hepcidin responds to iron status among those with either sickle cell trait or homozygous α+-thalassemia in young Kenyan children. This trial was registered at clinicaltrials.gov as NCT01704105.

Lower Plasma Soluble Transferrin Receptor Range in Healthy Indian Pediatric Cohort as Compared to Asian and Western Data

Soluble serum transferrin receptor is derived from erythroid transferrin receptor expressed on surface of developing erythroid cells. It can be detected in blood using sensitive ELISA methodology and blood levels reflect physiological iron dependent erythropoiesis state in bone marrow. Normal adult levels vary from 2 to 5 mg/l. However, pediatric studies are few and describe normal ranges to the tune of 1.0-3.0 mg/l, which are relatively lower than that of adults. In present study 40 healthy children (2-12 years) were evaluated to establish normal soluble transferrin receptor range. The mean transferrin receptor levels were 0.39 mg/l with a range of 0.17-2.1 mg/l. The levels were low as compared to mean levels described in other studies from West and our country (4.39 and 2.0 mg/l respectively). Since, no internationally standard method for reporting and testing for transferrin receptor levels are yet available, hence it is imperative to establish normal control ranges in different population cohorts, especially in pediatric age group, to better interpret their levels in diagnostic context.

Reference values of serum transferrin receptor (sTfR) and sTfR/log ferritin index in healthy children

ABSTARCT The aims of this study were to determine appropriate reference ranges for serum transferrin receptor (sTfR) and sTfR/log ferritin (sTfR-F index) in healthy children and their relationship with iron parameters, erythropoiesis, and other conditions presented by the subject. A total of 902 children with normal iron status, aged 1-11 years, were included in a cross-sectional study. A physical examination was conducted and z-score of body mass index (zBMI) obtained. Complete blood count, iron biomarkers, erythropoietin, C-reactive protein, sTfR, and sTfR/log ferritin were determined. Linear multiple regression was applied to identify the factors that determined sTfR and sTfR-F index variability. Mean values for sTfR and sTfR-F index were 1.22 ± 0.28 mg/L (95% confidence interval [CI]: 1.2-1.23) and 0.87 ± 0.25 (95% CI: 0.85-0.88). The reference intervals (2.5th to 97.5th percentiles [P2.5-P97.5]) were 0.78-1.9 mg/L and 0.49-1.46, respectively. sTfR and sTfR-F values decreased with age (P <.03 and P <.0001, respectively). No changes were observed with sex. Changes in sTfR and sTfR-F index were consistent with ferritin and erythropoietin variations. Iron biomarkers, erythropoietin, and zBMI predicted 19% and 18.1% of the sTfR and sTfR-F index variability. The results provide reference ranges for sTfR and sTfR-F index in healthy children for clinical use in the assessment of body iron status. Both biomarkers are predicted by iron parameters, erythropoietin, and zBMI.

Identifying factors predicting iron deficiency in United States adolescent females using the ferritin and the body iron models

BACKGROUND & AIMS

Iron deficiency is the most prevalent nutritional deficiency in the United States affecting 9-16% of female adolescents. With the primary purpose of detecting iron deficiency, primary care screening consists of a hemoglobin or hematocrit laboratory test. This method is simple and inexpensive, but tests for anemia, and is neither sensitive nor specific for iron deficiency. Alternate methods for diagnosing iron deficiency using the ferritin and body iron models are not widely utilized. The study objective was to compare iron deficiency risk factors among adolescent females defined by the ferritin and body iron models to better characterize those who may benefit from iron deficiency testing as opposed to the current anemia-based screen.

METHODS

This cross-sectional study of female adolescents aged 12-21 years utilized National Health and Nutrition Examination Survey 2003-2006 data. Anemia was defined by standard hemoglobin cutoffs. The ferritin model defines iron deficiency through transferrin saturation, ferritin and erythrocyte protoporphyrin laboratory testing. Body iron calculates iron status with a formula involving transferrin receptor and ferritin. Bivariate and multivariable analyses examined associations between questionnaire responses and iron deficiency defined by each model.

RESULTS

Among 1765 participants, 2.7% were anemic. Iron deficiency prevalence was 13.1% and 9.1% by the ferritin and body iron models, respectively. Based on the model, anemia-based screening had a sensitivity of 15.6-18.8% for iron deficiency. Multivariable associations for ferritin model iron deficiency included age, race/ethnicity, activity level and medroxyprogresterone acetate injection. Age and food insecurity were significant using the body iron model.

CONCLUSIONS

Universal anemia-based screening misses the majority of iron-deficient adolescent females. The common risk factor identified here, adolescent age, may both inform preventive care guidelines on age-based screenings and prospective studies of adolescent iron deficiency risk factors.

Reference values of serum transferrin receptor and sTfR/log ferritin index in healthy adolescents

Adolescence is a period of increased iron requirements, which impact on iron status. The purpose of this research is to determine the reference intervals for serum transferrin receptor (sTfR) and sTfR/log ferritin index (sTfR-F index) in healthy adolescents, and their relation with iron parameters and erythropoiesis. A total of 253 healthy adolescents without overweight, aged 12 to 16 years, were selected in a cross-sectional study. Hemoglobin, red cell indices, reticulocyte hemoglobin content (rHb), reticulocytes, ferritin, transferrin saturation, erythrocyte protoporphirin, erythropoietin, C-reactive protein, sTfR, and sTfR-F index were measured. Changes in erythropoiesis and iron status in the age interval were observed and analyzed, and linear multiple regression was applied to identify the factors that determine the variability of sTfR and sTfR-F index. Mean values for sTfR and sTfR-F index were 1.32 ± 0.3 mg/L (95% CI, 1.3-1.36) and 0.9 ± 0.25 (95% CI, 0.87-0.93). The reference intervals were 0.84 to 1.97 mg/L and 0.51 to 1.44, respectively. sTfR and sTfR-F index values were significantly higher in boys (1.39 ± 0.3 vs. 1.23 ± 0.26 mg/L, P<0.0001 and 0.93 ± 0.37 vs. 0.86 ± 0.22, P<0.04) and decreased with age (P<0.0001 and 0.04, respectively). No changes were recorded in erythropoietin. Age, sex, pubertal status, and ferritin predicted 24.1% of sTfR variability and age, sex, pubertal status, transferrin saturation, rHb, erythrocytes, and reticulocytes predicted 15% of sTfR-F index variability.

Neuroimaging, nutrition, and iron-related genes

Several dietary factors and their genetic modifiers play a role in neurological disease and affect the human brain. The structural and functional integrity of the living brain can be assessed using neuroimaging, enabling large-scale epidemiological studies to identify factors that help or harm the brain. Iron is one nutritional factor that comes entirely from our diet, and its storage and transport in the body are under strong genetic control. In this review, we discuss how neuroimaging can help to identify associations between brain integrity, genetic variations, and dietary factors such as iron. We also review iron's essential role in cognition, and we note some challenges and confounds involved in interpreting links between diet and brain health. Finally, we outline some recent discoveries regarding the genetics of iron and its effects on the brain, suggesting the promise of neuroimaging in revealing how dietary factors affect the brain.

Hepcidin expression from monocyte of splenectomized and non-splenectomized patients with HbE-β-thalassemia

OBJECTIVE

Hepcidin is a key regulator of body iron homeostasis. The inflammatory cytokine interleukin (IL)-6 has been reported to upregulate expression of the hepcidin (HAMP) gene in monocytes. The purpose of this work was to determine HAMP expression at steady state in monocytes of splenectomized and non-splenectomized patients with HbE-β-thalassemia compared with normal controls.

METHODS

Levels of HAMP mRNA were measured using real-time reverse transcriptase polymerase chain reaction. Plasma IL-6, soluble transferrin receptor (sTfR), and ferritin levels were determined by enzyme-linked immunosorbent assay, and C-reactive protein (CRP) by nephelometry.

RESULTS

Levels of HAMP mRNA, CRP, IL-6, sTfR, and ferritin were significantly higher in both groups of patients with thalassemia than controls, but were not different between splenectomized and non-splenectomized patients. Monocyte HAMP mRNA content of patients with thalassemia correlated with plasma IL-6 and CRP levels.

DISCUSSION

Patients with HbE-β-thalassemia have persistent elevation of the plasma inflammatory cytokines, CRP, and IL-6, and the latter could be responsible (in part) to the induction of HAMP expression in monocytes of patients with HbE-β-thalassemia.

Iron supplementation is positively associated with increased serum ferritin levels in 9-month-old Danish infants

Fe deficiency is still common in infancy, even in affluent societies, and has prompted Fe fortification of food products and use of Fe supplements in many populations. In the present study, we tested the hypothesis that Fe status among 9-month-old infants following the Danish Fe supplementation recommendation (>400 ml Fe-fortified formula or 8 mg Fe/d) is associated with more favourable levels of Fe status indicators compared to those not following the recommendation. A random sample of 9-month-old infants living in Copenhagen was established and 312 healthy term infants were examined at 9·1 (sd0·3) months of age. Blood samples were available from 278 infants. Overall, twenty infants (7·8 %) had Fe deficiency (serum ferritin < 12 μg/l) and < 1 % had Fe deficiency anaemia (serum ferritin < 12 μg/l and Hb < 100 g/l). Serum ferritin was positively associated with birth weight (P < 0·001), intake of fortified formula and follow-on formula (P = 0·001), and female sex (P < 0·001). Cow's milk intake and length of exclusive breast-feeding were negatively associated with Hb levels (P = 0·013 andP < 0·001). Serum ferritin levels were significantly higher (P < 0·0001) and transferrin receptor (TfR) was significantly lower (P = 0·003) among infants (n188) meeting the Fe supplementation recommendation compared to those (n67) not meeting the recommendation. No significant difference between these two groups was found for Hb. In conclusion, this study confirmed that Fe status of infants following the Danish Fe supplementation recommendation was significantly associated with increased serum ferritin and decreased levels of TfR indicating more favourable Fe status, compared to infants not following the recommendation.

Brain structure in healthy adults is related to serum transferrin and the H63D polymorphism in the HFE gene

Control of iron homeostasis is essential for healthy central nervous system function: iron deficiency is associated with cognitive impairment, yet iron overload is thought to promote neurodegenerative diseases. Specific genetic markers have been previously identified that influence levels of transferrin, the protein that transports iron throughout the body, in the blood and brain. Here, we discovered that transferrin levels are related to detectable differences in the macro- and microstructure of the living brain. We collected brain MRI scans from 615 healthy young adult twins and siblings, of whom 574 were also scanned with diffusion tensor imaging at 4 Tesla. Fiber integrity was assessed by using the diffusion tensor imaging-based measure of fractional anisotropy. In bivariate genetic models based on monozygotic and dizygotic twins, we discovered that partially overlapping additive genetic factors influenced transferrin levels and brain microstructure. We also examined common variants in genes associated with transferrin levels, TF and HFE, and found that a commonly carried polymorphism (H63D at rs1799945) in the hemochromatotic HFE gene was associated with white matter fiber integrity. This gene has a well documented association with iron overload. Our statistical maps reveal previously unknown influences of the same gene on brain microstructure and transferrin levels. This discovery may shed light on the neural mechanisms by which iron affects cognition, neurodevelopment, and neurodegeneration.

Effectiveness of a large-scale iron-fortified milk distribution program on anemia and iron deficiency in low-income young children in Mexico

BACKGROUND

Anemia during infancy impairs neurodevelopment. Little information has been published about the effectiveness of large-scale programs on anemia and iron-deficiency prevention.

OBJECTIVE

The objective was to assess the effectiveness of a large-scale program that distributes subsidized iron-fortified milk in Mexico on anemia and iron deficiency in children aged 12-30 mo.

DESIGN

A double-blinded, group-randomized effectiveness trial was conducted in 12 milk distribution clusters assigned to consume iron-fortified (FM; n = 7) or nonfortified (NFM; n = 5) milk. A daily portion of FM contained 5.28 mg Fe (ferrous gluconate) and 48 mg sodium ascorbate.

RESULTS

Overall treatment effects were documented at 6 and 12 mo for anemia and for iron deficiency assessed by both serum ferritin (SF) and serum soluble transferrin receptor (sTfR) (interaction: P < 0.10). Differential effects at 6 mo (P = 0.004) and 12 mo (P = 0.664) were documented only for sTfR. Estimated prevalences (EPs) of anemia (hemoglobin < 110 g/L) from baseline to 6 and 12 mo decreased from 42.6% to 19.7% and 9.4%, respectively, in the NFM group (n = 210) and from 44.5% to 12.7% and 4.0%, respectively, in the FM group (n = 357). EPs of SF < 12 mug/L from baseline to 6 and 12 mo changed from 36.0% to 41.8% and 17.1%, respectively, in the NFM group (n = 43) and from 29.8% to 18.6% and 5.7%, respectively, in the FM group (n = 144). EPs of sTfR > 3.3 mg/L from baseline to 6 and 12 mo decreased from 16.2% to 8.3% and 2.0%, respectively, in the NFM group (n = 114) and from 15.5% to 0.7% and 1.1%, respectively, in the FM group.

CONCLUSION

A large-scale iron-fortified subsidized-milk program was effective at reducing the rates of anemia and iron deficiency in Mexican children during 12 mo of implementation. This trial was registered at clinicaltrials.gov as NCT00508131.

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.

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.

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.

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.

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 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.

Iron overload in children who are treated for acute lymphoblastic leukemia estimated by liver siderosis and serum iron parameters

OBJECTIVE

To evaluate a secondary liver iron overload and its fate in children who are treated conventionally for acute lymphoblastic leukemia and to assess whether serum soluble transferrin receptor (sTfR) is useful in detecting iron load.

METHODS

Liver siderosis was estimated histologically from liver biopsy specimens of 30 children (aged 2.6-17.6 years) close to or at the end of therapy using total iron score (TIS). Serum iron parameters and sTfR were measured at the same time and in 22 patients 1 to 3 years after therapy.

RESULTS

In 19 (63%) of 30 patients, liver TIS was >15, indicating at least moderate iron overload. Serum ferritin, iron, and transferrin iron saturation levels were highest and transferrin level lowest in the patients with the highest liver iron content. Serum sTfR levels did not differ significantly between the patients with varying amounts of liver iron. TIS correlated most significantly positively with serum ferritin (r(S) = 0.899), transferrin iron saturation (r(S) = 0.764), and the amount of transfused red blood cells (r(S) = 0.783). Serum iron parameters normalized in most patients during the follow-up. In 3 (14%) of 22 patients, serum ferritin level remained high (>1000 microg/L).

CONCLUSIONS

Long-term iron overload is detected in at least 14% of children after therapy for acute lymphoblastic leukemia. Serum sTfR is an inappropriate marker for liver iron overload, whereas ferritin seems to be the most useful serologic marker for it.

Regression-based reference limits for urinary amino acids in a pediatric population

Age-related variation of the urinary excretion of amino acids has been widely reported. Instead of the conventional reference intervals, continuous reference limits might be a more practical approach during periods of rapid changes such as infancy or childhood. Regression-based reference limits have been produced for the urinary excretion of 23 amino acids analyzed in 148 healthy individuals from 0 to 12 years of age. Urinary excretion was modeled as a function of age by two parametric procedures: the polynomial and the piece-wise linear regression methods. Likewise, age-specific standard deviation was estimated by the regression of the absolute values of the residuals on age. Residual analysis was employed to select the best-fitting model and the 95% reference limits, and their 95% confidence intervals were calculated and plotted against the raw data. The urinary excretion of 19 amino acids decreased rapidly during the first year of life with a further slow decline thereafter. These amino acids fit better the piecewise model. The other four amino acids displayed a steady decrease in the urinary excretion from birth to puberty, and the excretion patterns fit better the quadratic or linear model. Fifteen amino acids showed a significant change in standard deviation with age. Regression-based reference limits differed consistently from conventional limits (<3 years) and narrower confidence intervals were obtained throughout the entire period studied. Avoiding partitioning gave rise to smoothly changing limits. Therefore, such alternative way of presenting amino acid reference limits may facilitate the follow-up of patients with inborn errors of amino acid metabolism.