Percentile estimates for transferrin receptor in normal infants 9-15 mo of age

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.

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.

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.

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.

Predictors of serum ferritin and serum soluble transferrin receptor in newborns and their associations with iron status during the first 2 y of life

BACKGROUND

Adequate iron status at birth may prevent iron deficiency in early childhood.

OBJECTIVES

We aimed to identify predictors of serum ferritin (SF) and serum soluble transferrin receptor (sTfR) in healthy newborns and to relate these iron indexes to iron status in the first 2 y of life.

DESIGN

Using bivariate correlations and linear regression, we related various factors in pregnancy to SF (n=363) and sTfR (n=350) in healthy, term infants. Measurements of cord SF and sTfR were compared with those of SF and sTfR at 6, 12, and 24 mo. All 4 measurements were available for 191 and 169 infants for SF and sTfR, respectively.

RESULTS

Geometric mean (and 95% CI) cord SF and sTfR measurements were 159 (148, 171) microg/L and 7.3 (7.0, 7.6) mg/L, respectively. Cord SF correlated with sTfR (rho=-0.21, P<0.001). In regression analysis, cord SF correlated with smoking and the use of iron supplements during pregnancy (partial r=-0.12 and 0.16; P<0.05 for both). Cord sTfR was associated with first trimester BMI, gestational age, and male sex (partial r=0.30, 0.24, and 0.19, respectively; P<0.01 for all). Cord SF correlated with SF at 6, 12, and 24 mo (rho=0.45, 0.31, and 0.16 respectively; P<0.05 for all). At age 6 mo, 16 of 17 infants with SF <15 mug/L were boys.

CONCLUSIONS

Cessation of smoking and adequate iron prophylaxis during pregnancy may improve iron status in infancy. Cord SF is a predictor of iron status in the first 2 y of life. Boys are at particular risk of low iron status in early infancy.

Children with autism: effect of iron supplementation on sleep and ferritin

To determine if there is a relationship between low serum ferritin and sleep disturbance in children with autism spectrum disorder, an 8-week open-label treatment trial with oral iron supplementation was conducted as a pilot study. At baseline and posttreatment visits, parents completed a Sleep Disturbance Scale for Children and a Food Record. Blood samples were obtained. Thirty-three children completed the study. Seventy-seven percent had restless sleep at baseline, which improved significantly with iron therapy, suggesting a relationship between sleep disturbance and iron deficiency in children with autism spectrum disorder. Sixty-nine percent of preschoolers and 35% of school-aged children had insufficient dietary iron intake. Mean ferritin increased significantly (16 microg/L to 29 microg/L), as did mean corpuscular volume and hemoglobin, suggesting that low ferritin in this patient group resulted from insufficient iron intake. Similar prevalence of low ferritin at school age as preschool age indicates that children with autism spectrum disorder require ongoing screening for 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.

Transferrin receptor in serum. A new tool in the diagnosis and prevention of iron deficiency in blood donors

BACKGROUND

Transferrin receptor mediates cellular uptake of iron, and the expression on cells reflects iron needs and erythropoietic activity. The results of measuring transferrin receptor in serum (sTfR) in blood donors are presented.

STUDY DESIGN AND METHODS

Haemoglobin, serum-ferritin and sTfR were measured in 172 female and 174 male donors that had donated whole blood six or more times during the previous 3 years and in 96 female and 56 male new donors.

RESULTS

Haemoglobin and sTfR were not significant different in new and repeat donors. New donors had significantly higher s-ferritin than repeat donors. Twenty donors had a Hb above the low limit for normal, but below the determined cut-off for donation. Only three of these had high sTfR and/or low serum-ferritin. Hence, of the total 492 donors 3.5% were below the Hb cut-off, but having Hb, s-ferritin and sTfR within normal ranges. 11.6% of new female donors belonged in this category.

CONCLUSION

STfR is better than s-ferritin as a screening for iron deficiency. Most donors with low tissue iron neither have high sTfR, nor anaemia. There is probably no need to have a separate, higher than the lower normal range, requirement for Hb in donors. STfR measurements are probably most valuable in a setting where most donors are repeat donors.

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.

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

BACKGROUND

The serum transferrin receptor (TfR) and the ratio of TfR to serum ferritin (TfR:SF) have been shown to be useful as early indicators of iron deficiency.

OBJECTIVE

The objective of this study was to evaluate the performance of TfR and TfR:SF in the assessment of iron deficiency in infants and to analyze age-related changes in both variables.

DESIGN

A total of 716 blood samples obtained from 515 healthy infants aged 8-15 mo were studied.

RESULTS

In 144 samples in which all other laboratory indicators of iron status were within the reference range, the median and 95% CI for TfR and TfR:SF were 8.5 mg/L (95% CI: 5.9, 13.5) and 497 (95% CI: 134, 975), respectively. TfR and TfR:SF were significantly correlated with the other laboratory indicators of iron status. Furthermore, as the severity of iron deficiency progressed, there was a gradual increase in mean TfR concentration (P: < 0.00001; analysis of variance). The sensitivity of TfR > 13.5 mg/L and TfR:SF > 975 in the diagnosis of iron deficiency was 23.6% and 68.4%, respectively. The specificity was 98.3% and 63.3% for TfR and TfR:SF, respectively. The sensitivity and specificity of SF < 10 microg/L were 63.7% and 60.8%, respectively. Receiver operator characteristic analysis showed that TfR and TfR:SF were more accurate than was SF alone in the diagnosis of iron deficiency.

CONCLUSIONS

TfR and TfR:SF showed age-related changes; TfR and TfR:SF appear to be better diagnostic tests for iron deficiency in infants than SF.

Clinical safety of iron-fortified formulas

BACKGROUND

Iron-fortified formulas are recommended throughout infancy and are frequently used beyond, yet safety aspects have been inadequately studied. Iron could theoretically increase pro-oxidant stress, with potential adverse effects, including infection risk, and some clinicians suspect that iron-fortified formulas induce gastrointestinal disturbance.

OBJECTIVE

A planned component of a large intervention trial has been to test the hypothesis that infants receiving iron-fortified formula do not have a higher incidence of infections (primary outcome) or gastrointestinal problems (secondary outcome) than infants on low iron-formulas or cow's milk. Methods. Children (n = 493) 9 months old receiving cow's milk were recruited in 3 UK centers and randomized to: 1) cow's milk as before, 2) formula containing.9 mg/L of iron, or 3) an otherwise identical formula but containing 12 mg/L of iron. Children were followed at 3 monthly intervals and the episodes of infections, diarrhea and constipation, and general morbidity to 18 months old were recorded. Hematologic indices of iron status were determined at 18 months old.

RESULTS

Serum ferritin concentrations were increased in infants receiving iron-fortified formula but there were no intergroup differences in incidence of infection, gastrointestinal problems, or in general morbidity or weight gain.

CONCLUSIONS

We were unable to identify adverse health effects in older infants and toddlers consuming a high iron-containing formula (12 mg/L) even when used in populations with a low incidence of iron deficiency.

The measurement of serum transferrin receptor

The concentration of the soluble fragment of transferrin receptor in serum is an important new hematological parameter. Clinical and laboratory studies have shown that this serum form of the receptor reflects the total body mass of cellular transferrin receptor, 80% of which is contained in the erythroid marrow. The two disorders that result in an elevation in the serum transferrin receptor are anemias associated with enhanced erythropoiesis and tissue iron deficiency. The concentration of soluble transferrin receptor provides a useful quantitative measure of the erythroid marrow mass and thereby assists clinically in categorizing the type of anemia. The most important clinical use of the serum transferrin receptor is in determining the cause of iron deficient erythropoiesis (that is, identifying iron deficiency anemia whether it occurs alone or in the presence of the anemia of chronic disease). Present evidence supports the routine use of the serum transferrin receptor in the clinical evaluation of anemic patients.

Structure, function and clinical significance of transferrin receptors

Iron plays an essential role in a spectrum of metabolic processes. Cellular iron uptake is facilitated by transferrin receptor (TfR)-mediated endocytosis. In recent years more insight has been obtained in TfR physiology and the regulation of cellular iron homeostasis. The synthesis of TfR and the iron storage protein ferritin is regulated reciprocally at the post-transcriptional level according to the cellular iron status. As a result of externalization of TfR during the endocytic cycle, a soluble form of TfR can be detected in serum. The serum TfR (sTfR) level is closely related to erythroid TfR turnover and the prime determinants of the sTfR concentration are cellular iron demands and erythroid proliferation rate. In the absence of a hyperplastic erythropoiesis the sTfR level is a sensitive parameter of early tissue iron deficiency. The entire spectrum of body iron status can be assessed by measurement of serum ferritin and sTfR levels, with ferritin as marker of tissue iron stores and sTfR as index of tissue iron needs. The sTfR may be a promising tool to detect iron deficiency in inflammatory states and in the anaemia of chronic disease as its concentration is, in contrast to ferritin levels, not influenced by the acute phase response. Determination of sTfR levels may also improve assessment of body iron stores during pregnancy and in neonates. Finally, the sTfR may be a useful parameter to monitor erythropoiesis in various clinical settings, for instance in the prediction of the haematological response to erythropoietin treatment. However, standardization of the sTfR assay, with definition of reference and pathological ranges, is necessary for the definitive introduction of the sTfR as major parameter of iron metabolism.