Diagnosis of Iron Deficiency in Infants

Serum hepcidin and ferritin as markers of iron deficiency in premature infants born at less than 32 weeks of gestation: prospective observational study

BACKGROUND

Preterm infants born at less than 32 weeks of gestation are at higher risk of low total iron stores (iron deficiency). Serum ferritin is used as a valid total iron stores and iron deficiency biomarker, usually as a combination of ferritin and red blood cell counts.

METHODS

Serum hepcidin and ferritin values and red blood cell counts were obtained from 37 of 40 included premature infants born at less than 32 weeks of gestation at risk of iron deficiency. The first sample was obtained in the first week of life, and the second at transfer from the Neonatal intensive care unit to the maternity ward, when serum ferritin level below 25 µg/L has been defined as very low total iron stores (iron deficiency).

RESULTS

Ferritin median levels decreased from a median value of 152 µg/L at the first measurement to 54 µg/L at the second measurement. Hepcidin median levels also decreased from 30.1 µg/L to 2.1 µg/L. We found a positive and statistically significant correlation between levels of ferritin and hepcidin at both measurements (r=0.57; P<0.001 and r=0.72; P<0.001, respectively). Compared to serum hepcidin, ferritin at the first measurement has not statistically significant higher power in predicting children with iron deficiency before discharge from the hospital.

CONCLUSIONS

We found a correlation between ferritin and hepcidin levels. Nevertheless, hepcidin does not have a worse power in predicting children with iron deficiency compared to ferritin.

Hyperferritinemia among very-low-birthweight infants in Thailand: a prospective cohort study

OBJECTIVES

To determine the incidence of hyperferritinemia in VLBW infants, and its association with neonatal morbidity.

STUDY DESIGN

Prospective cohort study in a tertiary-level hospital in Bangkok, from March 2022 to January 2023. Serum ferritin (SF) was measured in VLBW infants at one month and repeated monthly for those with hyperferritinemia (SF > 300 ng/mL).

RESULTS

Gestational age and birth weight were 29.7 ± 2.4 weeks (mean ± SD) and 1100 g (IQR, 830, 1340). Hyperferritinemia was identified in 30.1% (95% CI, 20.8-41.4). After adjustment, only packed red cell transfusion >15 mL/kg was associated with hyperferritinemia (RR 3.1; 95% CI, 1.5-6.4). All elevated SF levels returned to normal within four months. Hyperferritinemia was associated with severe bronchopulmonary dysplasia (RR 2.3, 95% CI, 1.0-5.4) and retinopathy of prematurity (RR 3.5, 95% CI, 1.4-8.6).

CONCLUSION

Hyperferritinemia is common among our VLBW infants, particularly after transfusion, and is associated with severe BPD and ROP.

Biomarkers of Brain Dysfunction in Perinatal Iron Deficiency

Iron deficiency in the fetal and neonatal period (perinatal iron deficiency) bodes poorly for neurodevelopment. Given its common occurrence and the negative impact on brain development, a screening and treatment strategy that is focused on optimizing brain development in perinatal iron deficiency is necessary. Pediatric societies currently recommend a universal iron supplementation strategy for full-term and preterm infants that does not consider individual variation in body iron status and thus could lead to undertreatment or overtreatment. Moreover, the focus is on hematological normalcy and not optimal brain development. Several serum iron indices and hematological parameters in the perinatal period are associated with a risk of abnormal neurodevelopment, suggesting their potential use as biomarkers for screening and monitoring treatment in infants at risk for perinatal iron deficiency. A biomarker-based screening and treatment strategy that is focused on optimizing brain development will likely improve outcomes in perinatal iron deficiency.

Control variables of serum ferritin concentrations in hospitalized newborn infants: an observational study

Both iron excess and deficiency are deleterious to cellular and organ homeostasis. Serum ferritin levels serve as a biomarker of iron storage; however, their distribution and determinants in sick newborn infants remain unclear. This study aimed to investigate the reference range and independent variables of serum ferritin in hospitalized newborn infants. All newborn infants who were hospitalized at a tertiary neonatal center within 24 h of birth were retrospectively reviewed for the period of April 2015 through March 2017. Serum ferritin levels were assessed using venous blood samples obtained at admission and their independent variables were explored. The study population comprised 368 infants (36.2 ± 2.8 weeks gestation and 2319 ± 623 g at birth), whose median serum ferritin level was 149 µg/L (inter-quartile range: 81-236). The multivariable model used to explain serum ferritin values comprised hemoglobin, lactate dehydrogenase, blood pH, and maternal hypertensive disorders in pregnancy (all p < 0.01, adjusted for sex and birth weight). Serum ferritin values in hospitalized newborn infants were comparable to those previously reported using umbilical cord blood. Our novel findings indicated the association between blood pH, lactate dehydrogenase, and ferritin levels, suggesting the influence of antenatal hypoxia-ischemia and stress to serum ferritin levels.

Reticulocyte Hemoglobin Equivalent has Comparable Predictive Accuracy as Conventional Serum Iron Indices for Predicting Iron Deficiency and Anemia in a Nonhuman Primate model of Infantile Iron Deficiency

BACKGROUND

Infantile iron deficiency (ID) causes anemia and compromises neurodevelopment. Current screening relies on hemoglobin (Hgb) determination at 1 year of age, which lacks sensitivity and specificity for timely detection of infantile ID. Low reticulocyte Hgb equivalent (RET-He) indicates ID, but its predictive accuracy relative to conventional serum iron indices is unknown.

OBJECTIVES

The objective was to compare diagnostic accuracies of iron indices, red blood cell (RBC) indices, and RET-He for predicting the risk of ID and IDA in a nonhuman primate model of infantile ID.

METHODS

Serum iron, total iron binding capacity, unsaturated iron binding capacity, transferrin saturation (TSAT), Hgb, RET-He, and other RBC indices were determined at 2 wk and 2, 4, and 6 mo in breastfed male and female rhesus infants (N = 54). The diagnostic accuracies of RET-He, iron, and RBC indices for predicting the development of ID (TSAT < 20%) and IDA (Hgb < 10 g/dL + TSAT < 20%) were determined using t tests, area under the receiver operating characteristic curve (AUC) analysis, and multiple regression models.

RESULTS

Twenty-three (42.6%) infants developed ID and 16 (29.6%) progressed to IDA. All 4 iron indices and RET-He, but not Hgb or RBC indices, predicted future risk of ID and IDA (P < 0.001). The predictive accuracy of RET-He (AUC = 0.78, SE = 0.07; P = 0.003) for IDA was comparable to that of the iron indices (AUC = 0.77-0.83, SE = 0.07; P ≤ 0.002). A RET-He threshold of 25.5 pg strongly correlated with TSAT < 20% and correctly predicted IDA in 10 of 16 infants (sensitivity: 62.5%) and falsely predicted possibility of IDA in only 4 of 38 unaffected infants (specificity: 89.5%).

CONCLUSIONS

RET-He is a biomarker of impending ID/IDA in rhesus infants and can be used as a hematological parameter to screen for infantile ID.

Effects of latent iron deficiency on auditory neural maturation during early infancy in infants above 35 weeks' gestation

BACKGROUND

Latent iron deficiency (LID) at birth is associated with prolonged latencies in auditory brainstem response (ABR), a surrogate for neural maturation. This study aimed to compare wave and inter-peak latencies of ABR at birth and at 4-6 months of age in infants ≥35 weeks of gestation with normal iron status (NIS) and LID.

METHODS

Neonates born at ≥35 weeks were screened. Cord ferritin value ≤ 75 ng/mL and >75 ng/mL were classified as LID and NIS, respectively. ABR was performed within 48 h of birth. The absolute latencies of waves I, III, and V, and inter-peak latencies I-III, III-V, and I-V were computed. Infants were reassessed at 4-6 months of age for hemoglobin, serum ferritin levels, and ABR latencies.

RESULTS

In total, 160 neonates were enrolled. The mean (SD) birth weight and gestational age of the study population were 2843 (384) g and 38.3 (1.1) weeks, respectively. Approximately 122 infants completed follow-up until 4-6 months of age: 37 in the LID group and 85 in the NIS group. Overall, the wave and interpeak latencies in both groups at birth were comparable. At 4-6 months, the absolute latencies of waves I, III, and V, and inter-peak latencies I-III, III-V, and I-V were decreased and were comparable in both groups. Among small-for-gestational-age neonates, inter-peak latencies in I-III and I-V at birth were significantly longer in the LID group than in the NIS group. Nine (24.3%) infants in the LID group and none in the NIS group were iron-deficient at 4-6 months of age.

CONCLUSION

There was no difference in wave or inter-peak latencies at birth and at 4-6 months of age in neonates aged ≥35 weeks with or without LID. However, infants with LID at birth have a significant risk of iron deficiency at 4-6 months of age. CTRI/2017/08/009379 (www.ctri.nic.in).

Iron Deficiency Anemia at Time of Vaccination Predicts Decreased Vaccine Response and Iron Supplementation at Time of Vaccination Increases Humoral Vaccine Response: A Birth Cohort Study and a Randomized Trial Follow-Up Study in Kenyan Infants

Background: Iron deficiency may impair adaptive immunity and is common among African infants at time of vaccination. Whether iron deficiency impairs vaccine response and whether iron supplementation improves humoral vaccine response is uncertain.

Methods: We performed two studies in southern coastal Kenya. In a birth cohort study, we followed infants to age 18 mo and assessed whether anemia or iron deficiency at time of vaccination predicted vaccine response to three-valent oral polio, diphtheria-tetanus-whole cell pertussis-Haemophilus influenzae type b vaccine, ten-valent pneumococcal-conjugate vaccine and measles vaccine. Primary outcomes were anti-vaccine-IgG and seroconversion at age 24 wk and 18 mo. In a randomized trial cohort follow-up, children received a micronutrient powder (MNP) with 5 mg iron daily or a MNP without iron for 4 mo starting at age 7.5 mo and received measles vaccine at 9 and 18 mo; primary outcomes were anti-measles IgG, seroconversion and avidity at age 11.5 mo and 4.5 y.

Findings: In the birth cohort study, 573 infants were enrolled and 303 completed the study. Controlling for sex, birthweight, anthropometric indices and maternal antibodies, hemoglobin at time of vaccination was the strongest positive predictor of: (A) anti-diphtheria and anti-pertussis-IgG at 24 wk (p = 0.0071, p = 0.0339) and 18 mo (p = 0.0182, p = 0.0360); (B) anti-pertussis filamentous hemagglutinin-IgG at 24 wk (p = 0.0423); and (C) anti-pneumococcus 19 IgG at 18 mo (p = 0.0129). Anemia and serum transferrin receptor at time of vaccination were the strongest predictors of seroconversion against diphtheria (p = 0.0484, p = 0.0439) and pneumococcus 19 at 18 mo (p = 0.0199, p = 0.0327). In the randomized trial, 155 infants were recruited, 127 and 88 were assessed at age 11.5 mo and 4.5 y. Compared to infants that did not receive iron, those who received iron at time of vaccination had higher anti-measles-IgG (p = 0.0415), seroconversion (p = 0.0531) and IgG avidity (p = 0.0425) at 11.5 mo.

Interpretation: In Kenyan infants, anemia and iron deficiency at time of vaccination predict decreased response to diphtheria, pertussis and pneumococcal vaccines. Primary response to measles vaccine may be increased by iron supplementation at time of vaccination. These findings argue that correction of iron deficiency during early infancy may improve vaccine response.

Iron Homeostasis Disruption and Oxidative Stress in Preterm Newborns

Iron is an essential micronutrient for early development, being involved in several cellular processes and playing a significant role in neurodevelopment. Prematurity may impact on iron homeostasis in different ways. On the one hand, more than half of preterm infants develop iron deficiency (ID)/ID anemia (IDA), due to the shorter duration of pregnancy, early postnatal growth, insufficient erythropoiesis, and phlebotomy losses. On the other hand, the sickest patients are exposed to erythrocytes transfusions, increasing the risk of iron overload under conditions of impaired antioxidant capacity. Prevention of iron shortage through placental transfusion, blood-sparing practices for laboratory assessments, and iron supplementation is the first frontier in the management of anemia in preterm infants. The American Academy of Pediatrics recommends the administration of 2 mg/kg/day of oral elemental iron to human milk-fed preterm infants from one month of age to prevent ID. To date, there is no consensus on the type of iron preparations, dosages, or starting time of administration to meet optimal cost-efficacy and safety measures. We will identify the main determinants of iron homeostasis in premature infants, elaborate on iron-mediated redox unbalance, and highlight areas for further research to tailor the management of iron metabolism.

Reticulocyte hemoglobin content as an early predictive biomarker of brain iron deficiency

BACKGROUND

Fetal and neonatal brain iron content is compromised at the time of anemia, suggesting that screening for iron deficiency by measuring hemoglobin is inadequate to protect the brain. Reticulocyte hemoglobin (Ret-He) reflects iron-deficient (ID) erythropoiesis prior to anemia.

METHODS

At postnatal day (P), 10 and 20 iron-sufficient rat pups were fostered to ID dams to produce a postnatal ID (PNID) group, which was compared to 20 iron-sufficient (IS) pups fostered by IS dams. Pups were assessed from P13 to P15 for hemoglobin, hematocrit, reticulocyte count, and Ret-He. Hippocampal iron status was assessed by transferrin receptor-1 (Tfrc-1) and divalent metal transporter-1 (Slc11a2) mRNA expression.

RESULTS

At P13, brain iron status was similar between groups; only Ret-He was lower in the PNID group. At P14, the PNID group had lower Ret-He, hematocrit, mean corpuscular volume (MCV), and reticulocyte percentage (RET%). Tfrc-1 expression was increased, consistent with brain iron deficiency. Both Ret-He and MCV correlated with brain iron status at P14 and P15.

CONCLUSIONS

Ret-He was the only red cell marker affected prior to the onset of brain ID. The clinical practice of using anemia as the preferred biomarker for diagnosis of iron deficiency may need reconsidering.

Iron status in small for gestational age and appropriate for gestational age infants at birth

PURPOSE

This study compared the iron statuses of small for gestational age (SGA) and appropriate for gestational age (AGA) infants at birth.

METHODS

The clinical data of 904 newborn infants admitted to the neonatal intensive care unit were reviewed. Blood samples were drawn from the infants within 24 hours after birth. Serum ferritin level was used as a marker of total iron status.

RESULTS

In this study, 115 SGA (GA, 36.5±2.9 weeks; birth weight [BW], 1,975±594.5 g) and 717 AGA (GA, 35.1±3.5 weeks; BW, 2,420.3±768.7 g) infants were included. The SGA infants had higher hematocrit levels (50.6%±5.8% vs. 47.7%±5.7%, P<0.05) than the AGA infants. No difference in serum ferritin level (ng/mL) was found between the groups (mean [95% confidence interval]: SGA vs. AGA infants, 139.0 [70.0-237.0] vs. 141.0 [82.5-228.5]). After adjusting for gestational age, the SGA infants had lower ferritin levels (147.1 ng/mL [116.3-178.0 ng/mL] vs. 189.4 ng/mL [178.0-200.8 ng/ mL], P<0.05). Total body iron stores were also lower in the SGA infants than in the AGA infants (185.6 [153.4-211.7] vs 202.2 [168.7-241.9], P<0.05).

CONCLUSION

The SGA infants had lower ferritin and total body iron stores than the AGA infants. The SGA infants affected by maternal hypertension who were born at late preterm had an additional risk of inadequate iron store. Iron deficiency should be monitored in these infants during follow-up.

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.

Prenatal Iron Deficiency, Neonatal Ferritin, and Infant Cognitive Function

OBJECTIVE

To investigate the impact of prenatal maternal iron deficiency (ID) on cord blood serum ferritin (CBSF) concentration and infant cognitive and motor development.

METHODS

Our prospective cohort study included 636 mother-singleton child pairs from 828 eligible pregnant women who were enrolled during their first antenatal care (ANC) visit in Allada, Benin, into a clinical trial comparing the efficacy of mefloquine and sulfadoxine-pyrimethamine. Venous blood samples of women were assessed for ferritin and hemoglobin concentrations at the first and second ANC visits (occurring at least 1-month apart) and at delivery. Women were prescribed daily iron and folic acid supplements throughout pregnancy. Hematologic examinations were repeated for cord blood at birth. At age 1 year, cognitive and motor functions of children were assessed by using the Mullen Scales of Early Learning.

RESULTS

The prevalence of prenatal ID at first and second ANC visits, and at delivery was 30.5%, 34.0%, and 28.4%, respectively. CBSF concentrations were similar between ID and non-ID pregnant women. Neither prenatal ID nor CBSF concentration was associated with poor cognitive or gross motor function of children at age 1 year. CBSF concentrations were lower among mothers who had ID anemia (IDA) at delivery compared with non-IDA pregnant women (adjusted mean difference: -0.2 [95% confidence interval: -0.4 to -0.0]).

CONCLUSIONS

In a malaria-endemic region, ID in pregnancy in the context of iron supplementation is neither associated with CBSF concentration nor with infant cognitive and motor development. Prenatal IDA around the time of delivery is associated with lower CBSF concentrations.

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.

Perinatal role of hepcidin and iron homeostasis in full-term intrauterine growth-restricted infants

OBJECTIVES

To prospectively investigate iron homeostasis in full-term intrauterine growth-restricted (IUGR) and appropriate-for-gestational-age (AGA) infants at birth, by evaluating cord blood concentrations of hepcidin (a bioactive molecule, principal regulator of iron metabolism, downregulated by hypoxia/iron deficiency and upregulated by inflammation), erythropoietin (EPO, a marker of prolonged fetal hypoxia), soluble transferrin receptor (sTfR, a marker of increased erythropoiesis and tissue iron deficiency), iron, ferritin, and unsaturated iron-binding capacity (UIBC).

METHODS

Serum cord blood samples from 47 well-defined IUGR and 104 AGA singleton, full-term infants were analyzed for concentrations of all the aforementioned parameters by enzyme immunoassays and spectrophotometry.

RESULTS

Hepcidin concentrations were similar, while EPO concentrations were higher in IUGR cases than in AGA controls (P = 0.047). Cord blood sTfR concentrations were increased in IUGR, compared to AGA infants (P = 0.004), and negatively correlated with their customized centiles and birth weight (r = -0.238, P = 0.003 and r = -0.157, P = 0.050, respectively). Ferritin concentrations were lower in IUGR cases than in AGA controls (P = 0.039). In both groups, no correlations were observed between cord blood hepcidin concentrations and iron status indices.

CONCLUSIONS

Cord blood hepcidin concentrations in term IUGRs may remain unaffected, possibly due to a balance between hepcidin downregulation by chronic fetal hypoxia (indicated by higher EPO concentrations) and impaired iron metabolism (indicated by lower ferritin and higher sTfR concentrations) on the one hand, and hepcidin upregulation by the inflammatory state characterizing IUGRs, on the other. Furthermore, our findings may possibly indicate the need for regular follow-up for detection of iron-deficient anemia, not only in preterm but also in full-term IUGR neonates.

Consequences of low neonatal iron status due to maternal diabetes mellitus on explicit memory performance in childhood

Diabetic pregnancies are characterized by chronic metabolic insults, including iron deficiency, that place the developing brain at risk for memory impairment later in life. A behavioral recall paradigm coupled with electrophysiological measures was used to assess the longevity of these effects in 40 3(1/2)-year-old children. When memory demands were high, recall was significantly impaired in the at-risk group and correlated with perinatal measures of iron. Electrophysiological results suggested both encoding and retrieval processes were compromised. These findings support the hypothesis that prenatal iron deficiency leads to alterations in neural development that have a lasting impact on memory ability.

Iron therapy for preterm infants

Preterm infants are at risk for both iron deficiency and iron overload. The role of iron in multiple organ functions suggests that iron supplementation is essential for the preterm infant. Conversely, the potential for iron overload and the poorly developed antioxidant measures in the preterm infant argue against indiscriminate iron supplementation in this population. This article reviews the predisposing factors and consequences of iron deficiency and iron overload in the preterm infant, discusses the current recommendation for iron supplementation and its appropriateness, and describes potential management strategies that strike a balance between iron deficiency and iron toxicity.