The Measurement of Serum Transferrin Receptor

Physiologically based serum ferritin thresholds for iron deficiency among women and children from Africa, Asia, Europe, and central America: a multinational comparative study

BACKGROUND

Diagnosis of iron deficiency commonly relies on measurement of serum ferritin concentrations. WHO guidelines identify serum ferritin thresholds for iron deficiency among healthy individuals of less than 15 μg/L for women and less than 12 μg/L for children under 5 years, based on expert opinion. We report thresholds for iron deficiency for apparently healthy non-pregnant women and young children based on physiological indicators.

METHODS

We performed secondary analyses of cross-sectional data from women (aged 15-49 years) and children (aged 6-59 months) from 12 countries in Africa, Asia, Europe, and central America from available surveys (2007-19). Using haemoglobin and soluble transferrin receptor concentrations as individual-level indicators of iron deficiency, we identified country-specific serum ferritin thresholds. We conducted multivariate meta-analysis using individual participant data to assess multinational heterogeneity and intercountry consistency.

FINDINGS

Data were collected from July, 2007 to March, 2019. 18 251 individuals (13 864 women and 4387 children) were included in the final analysis. The thresholds of pooled serum ferritin levels corresponding to the starting point of decline in circulating haemoglobin concentrations were 24·8 μg/L (95% CI 24·4-25·2) for women and 22·1 μg/L (20·8-23·4) for children based on the national survey data from 12 countries. The thresholds were consistent among countries (pheterogeneity: women=0·73, children=0·43) but median serum ferritin concentrations and lower 5% reference ranges differed. In all countries, the prevalence of iron deficiency was higher using physiologically based thresholds than that using WHO current guidelines for women (36·0% [95% CI 25·3-46·8] vs 20·1% [11·5-28·7], p<0·0001) and for children (34·2% [24·3-44·1] vs 16·6% [11·2-22·0], p<0·0001).

INTERPRETATION

These results provide evidence that the prevalence of iron deficiency as indicated by physiological measures is substantially higher than those based on current WHO guidelines. The consistency of physiologically based serum ferritin thresholds in apparently healthy women and young children offers a potential means to achieve evidence-informed coordination in thresholds for iron deficiency across populations. The use of physiologically based serum ferritin thresholds could help in detecting the clinical and functional outcomes of iron deficiency.

FUNDING

None.

Physiologically based trimester-specific serum ferritin thresholds for iron deficiency in US pregnant women

ABSTRACT

Serum ferritin (SF) concentration is the most widely used indicator for iron deficiency (ID). During pregnancy, the World Health Organization recently recommended SF thresholds for ID of <15 μg/L for the first trimester of pregnancy, based on expert opinion, and made no recommendations for the second and third trimesters. We examined the relationship of SF with 2 independent indicators of the onset of iron-deficient erythropoiesis, hemoglobin and soluble transferrin receptor 1, in cross-sectional data from US National Health and Nutrition Examination Survey for 1999 to 2010 and 2015 to 2018. We included 1288 pregnant women aged 15 to 49 years and excluded women with inflammation or potential liver disease. We used restricted cubic spline (RCS) regression analysis to determine SF thresholds for iron-deficient erythropoiesis. SF decreased during pregnancy; geometric mean SF was higher during the first and lower during the second and third trimesters. Using RCS analysis, the SF thresholds identified during pregnancy were <25.8 μg/L (18.1-28.5) during first trimester, <18.3 μg/L (16.3-22.9) during second trimester, and <19.0 μg/L (14.4- 26.1) during third trimester. These SF threshold levels track concentrations of hepcidin, the iron-regulatory hormone controlling the mobilization of iron stores. An SF concentration of <15 μg/L as the criterion for ID may underestimate the true prevalence of ID throughout pregnancy. In our study, an additional 1 of every 10 pregnant women would be recognized as iron deficient by using the physiologically based thresholds at SF of ∼25 μg/L during the first and ∼20 μg/L during the second and third trimesters.

Physiologically based serum ferritin thresholds for iron deficiency in women of reproductive age who are blood donors

Our objective is to develop a physiologically based method to determine serum ferritin thresholds for iron deficiency in healthy individuals. The current World Health Organization threshold of <15 µg/L for iron deficiency in women is based on expert opinion. We examined the relationship between serum ferritin and two independently measured indicators of iron-deficient erythropoiesis, soluble transferrin receptor (sTfR) and hemoglobin, in baseline data from 286 women, 20-49 years, who were first-time or reactivated donors in the REDS-II Donor Iron Status Evaluation (REDS-RISE) study. At lower serum ferritin concentrations, median sTfR increased as hemoglobin decreased. Using restricted cubic spline regression analysis to determine thresholds for iron-deficient erythropoiesis, the thresholds identified by sTfR (serum ferritin <25.4 µg/L) and by hemoglobin (serum ferritin <25.3 µg/L) did not differ significantly. The thresholds found in the REDS-RISE study do not differ from those identified by sTfR (serum ferritin <25.5 µg/L) and hemoglobin (serum ferritin <26.6 µg/L) in a previous study of 5,442 women, 20-49 years, in the U.S. National Health and Nutrition Examination Survey 2003-2018 (NHANES) (p=0.98 and 0.83, respectively). While international comparisons are needed, these results with US data provide additional evidence for the potential usefulness of a physiologically based method to identify serum ferritin thresholds for iron deficiency.

Dose Effect of Bovine Lactoferrin Fortification on Iron Metabolism of Anemic Infants

To evaluate the effect of iron-fortified formula with different concentrations of bovine lactoferrin (bLF) on improvement of anemic status in term infants who were previously breast-fed. A randomized, controlled, open, and post-market intervention study. A total of 108 infants aged 6-9 mo who were previously breast-fed and weaned were selected. The subjects were divided into three groups with the sequence of outpatient: fortified group 1 (FG1) with a bLF concentration of 38 mg/100 g, FG2 with 76 mg/100 g bLF, FG0 with no bLF. The intervention duration was 3 mo. Weight, height, head circumference and the concentration of hemoglobin (Hb), serum ferritin (SF), serum transferring receptor (sTfR) were measured and sTfR-SF index (TFR-F index) and total body iron content (TBIC) were computed before and after intervention. The primary outcome measures were obtained from 96 infants (35, 33 and 28 for FG0, FG1 and FG2, respectively). After 1 mo of intervention, the changes of Hb level showed no significant difference (p>0.05) among the three groups, however, the Hb level of infants in FG2 were significantly higher than those of infants in the other two groups after 3 mo of intervention (p<0.05). The present data indicated that the formula fortified with 76 mg/100 g bLF positively affected the Hb of anemic infants who were previously breastfed when compared with fortification with 38 mg/100 g bLF and no bLF fortification.

Iron and peripheral arterial disease: revisiting the iron hypothesis in a different light

The relationship between iron status and atherosclerosis has long been a topic of debate in the literature. Despite more than 25 years of research, there is no consensus regarding a causal relationship. To date, the vast majority of studies have focused on iron burden with respect to a hypothesized role in the onset and progression of coronary artery disease. However, the effect of iron in the coronary arterial system may differ mechanistically and therefore clinically from its effect in the peripheral arterial system. This review will summarize the biochemical, pathologic, animal, and clinical research data with respect to iron and atherosclerosis. This background will be expanded upon to provide insights into ongoing studies and paths for future investigations into the role of iron and peripheral arterial disease.

Perception of iron deficiency from oral mucosa alterations that show a high prevalence of Candida infection

BACKGROUND/PURPOSE

Iron deficiency (ID) is the most common cause of anemia. The aim of this study was to investigate patients with oral mucosa alterations as the initial manifestation of ID or ID anemia (IDA).

METHODS

Sixty-four patients (50 IDA and 14 ID) with a wide range of sore mouth were diagnosed and treated. The oral and physical manifestations as well as iron studies and anemia classification based on the mean and heterogeneity of red cell size were assessed.

RESULTS

ID predisposed 64 patients to a high incidence of Candida infection (85%) and showed a variety of oral manifestations including angular cheilitis (63%), atrophic glossitis (AG; 59%), pseudomembranous candidosis (44%), erythematous candidosis (41%), median rhomboid glossitis (5%), chronic mucocutaneous candidosis (5%), papillary hyperplastic candidosis (3%), and cheilocandidosis (3%). Others included pale oral mucosa (31%), burning mouth (28%), and recurrent oral ulcers (6%). Colorectal cancers in two patients were diagnosed. The values of hemoglobin (Hb) in 64 ID patients varied from normal to life-threatening levels, but none had developed advanced systemic symptoms except fatigue. All had low serum iron and ferritin. Sixty (94%) patients had transferrin saturation < 16%; however, 19 (30%) patients remained normocytic and 14 (22%) patients were nonanemic.

CONCLUSION

The study demonstrates that oral mucosa alterations accompanying oral candidosis are a sensitive indicator of ID. All oral changes can be successfully ameliorated by iron therapy plus antifungals when candidosis exists. Investigating the origin of IDA is necessary, because it may be the first sign of a more serious disease, particularly malignancy.

Reticulocyte parameters of delta beta thalassaemia trait, beta thalassaemia trait and iron deficiency anaemia

AIMS

To analyse the differences in reticulocyte indices between delta beta thalassaemia trait (δβ-TT), beta thalassaemia trait (β-TT) and iron deficiency anaemia (IDA), and to correlate those differences with the physiopathological features of these three types of microcytoses.

METHODS

We performed a descriptive study of 428 samples (43 δβ-TT, 179 β-TT and 206 IDA) that were run on Advia 2120 analyser (Siemens). The following reticulocyte indices were assessed: absolute reticulocyte count (ARC), percentage of reticulocytes, mean corpuscular volume of reticulocytes (MCVr), haemoglobin content of reticulocytes (CHr), mean corpuscular haemoglobin concentration of reticulocytes, red blood cell distribution width of reticulocytes (RDWr), haemoglobin distribution width of reticulocytes (HDWr) and reticulocyte subpopulations based on their fluorescence according to mRNA (low (L-R), medium (M-R) and high (H-R)), MCV ratio and MCHC ratio. Correlation between fetal haemoglobin (HbF) and RDWr in patients with thalassaemia was evaluated.

RESULTS

RDWr was significantly higher in δβ-TT compared with β-TT (15.03% vs 13.82%, p<0.001), and so were HDWr (3.65% vs 3.27%, p<0.001), CHr (23.68 vs 22.66 pg, p<0.001) and MCVr (88.3 vs 85.5 fL, p<0.001). A good correlation was observed between HbF and RDWr (r=0.551, p<0.001). IDA subjects have more immature reticulocytes, but less ARC than β-TT, suggesting a certain degree of inefficient erythropoiesis in IDA in comparison with β-TT.

CONCLUSIONS

Previously described differences between δβ-TT, β-TT and IDA in the corpuscular indices of mature red blood cell can also be observed in reticulocytes. The degree of anisocytosis in reticulocytes from patients with thalassaemia is correlated with HbF.

Erythropoiesis versus inflammation in Hereditary Spherocytosis clinical outcome

OBJECTIVES

This study aimed to evaluate the relationship between erythropoiesis and inflammation, in Hereditary Spherocytosis (HS) clinical outcome.

DESIGN AND METHODS

We studied 26 controls and 82 HS patients presenting mild (n = 49) and severer (n = 33) HS forms. We evaluated plasma levels of EPO, sTfR, ferritin, iron, folic acid, vitamin B12, TNF-α, IFN-γ, elastase and lactoferrin; leukocyte and reticulocyte counts and RPI were determined.

RESULTS

All HS patients showed significantly higher EPO, sTfR, reticulocytes and RPI but only mild HS presented normal hemoglobin levels; the positive significant correlations between EPO and sTfR, reticulocytes and RPI observed in mild HS were not observed in severer HS patients. HS patients presented with higher levels of neutrophils, TNF-α, IFN-γ, elastase, lactoferrin and ferritin.

CONCLUSIONS

Our data show HS as a disease linked to enhanced erythropoiesis that is disturbed in the more severe forms, to which inflammation may contribute, at least in part.

Comparison of plasma ferritin concentration with the ratio of plasma transferrin receptor to ferritin in estimating body iron stores: results of 4 intervention trials

BACKGROUND

Efforts to develop global programs for the control of iron deficiency require simple, low-cost, and accurate indicators of iron status.

OBJECTIVE

We aimed to compare estimates of body iron (BI) stores, as calculated from either plasma ferritin concentration alone (BI-ferritin) or the ratio of plasma transferrin receptor (TfR) to ferritin (BI-TfR/ferritin).

DESIGN

Data were analyzed from 4 previously completed, randomized intervention trials that enrolled infants, schoolchildren, or pregnant women (total n = 1189, after excluding subjects with elevated C-reactive protein).

RESULTS

The correlation coefficients between BI-ferritin and BI-TfR/ferritin were >0.95 for all studies. The kappa index ranged from 0.5 to 1.0. All of the sensitivities of BI-ferritin for identifying persons with low iron stores (defined as BI-TfR/ferritin < 0 mg/kg body wt) were >0.90. All of the specificities were >0.90 except the study of pregnant women (specificity = 0.66). The effect sizes of iron intervention trials were significantly greater for change in iron reserves estimated by BI-TfR/ferritin than by BI-ferritin in 2 studies with larger effect sizes (1.11 compared with 1.00 and 1.56 compared with 1.44, respectively; P < 0.05) and 1 study with medium effect size (0.70 compared with 0.57; P < 0.05). However, there were no significant differences between estimates of these effect sizes for 1 study with a medium effect size and 1 study with a smaller effect size (0.78 compared with 0.83 and 0.37 compared with 0.35, respectively; P > 0.2).

CONCLUSION

Plasma ferritin concentration alone provides a good approximation of total BI reserves, as estimated by BI-TfR/ferritin, on the basis of high correlation, sensitivity, and specificity among nonpregnant persons with unelevated C-reactive protein.

Elevated iron status strongly predicts mortality in West African adults with HIV infection

OBJECTIVE

To comprehensively assess iron status and determine whether elevated iron status, like anemia, predicts mortality.

METHODS

We followed 1362 Gambian adults (53% female) in an HIV-seroprevalent clinic-based cohort over 11.5 years to ascertain all-cause mortality. Baseline iron status (iron, soluble transferrin receptor [sTfR], transferrin, ferritin, transferrin saturation, log [transferrin receptor: ferritin]), age, gender, ethnicity, hemoglobin, body mass index, HIV type, absolute CD4 count, malaria status, and [alpha]-(1)-antichymotrypsin were measured.

RESULTS

The mortality rate was 25.9/100 person-years. Elevated iron universally predicted greater mortality compared to normal iron status for all iron status indices, with the exception of sTfR in unadjusted models. In fully adjusted models, transferrin (elevated vs. normal, hazard ratio [HR]: 1.77; 95% confidence interval [CI]: 1.30 to 2.42; P < 0.001), ferritin (elevated vs. normal, HR: 1.40; 95% CI: 1.07 to 1.83; P = 0.014), and the combined iron status index (highly elevated vs. normal, HR: 2.20; 95% CI: 1.16 to 4.18; P = 0.016) remained significant predictors. As expected, hemoglobin (Hb) concentration and absolute CD4 counts were each inversely associated with mortality.

CONCLUSIONS

Elevated iron status predicts mortality in HIV infection, even after adjustment for immunosuppression and other confounders. This finding has implications in the clinical monitoring of disease progression and for iron-supplementation practices in areas of high HIV prevalence.

Silent angiodysplasia and occult haemobilia as rare but treatable causes of refractory iron deficiency--two case reports

Once menorrhagia has been excluded in females then, in both sexes, the gastrointestinal tract remains the commonest site for haemorrhage. This may be of surprisingly large volume but intermittent and therefore not universally demonstrated on stool testing. However, if loss is persistent it may nevertheless culminate in absolute iron deficiency and thus, even when occult blood is not present on repeated examinations, quantitation using chromium labelled red cells becomes invaluable. In this situation, endoscopy or contrast radiology of the small and large bowel may fail to reveal any lesion even when these procedures are repeated or used in combination. Modifications by direct inspection or camera study may be helpful in improving diagnostic accuracy. It is nevertheless practical, as illustrated by these two cases, to more widely recognise the value of radionuclide scanning methods. In one this was due to unsuspected haemobilia and the second to major duodenal vascular malformation although it could be reasonably argued that initial recourse to angiography might have demonstrated this. The principle is that when precisely defined anatomically surgery can be elective and limited as a result of careful proactive planning and operations likely to have a high initial rate of success. The role of nuclear medicine in the investigative algorithm of such patient is re-emphasised. Thus, in any individual with unexplained but proven absolute iron deficiency failure to reveal the cause by first screening with gastroscopy and colonoscopy or barium studies including the small bowel should not automatically be repeated. Rather, the blood loss needs to be documented and, if possible, subsequent evaluation moved to advancement or push enteroscopy, capsule endoscopy or the more invasive angiography only once quantity a pattern of bleeding are defined by radioisoptic imaging.

Immunological study of complex formation between soluble transferrin receptor and transferrin

Transferrin receptor (TfR) is a dimeric transmembrane protein that provides iron transport from plasma to cells by binding and internalization of iron-loaded transferrin (Tf). Soluble transferrin receptor (sTfR) is an extracellular part of the TfR molecule that is truncated from the cell surface and released into the blood stream. Using monoclonal antibodies (HyTest Ltd., Turku, Finland), immunofluorescent methods for sTfR and sTfR-Tf complex determination were developed. Soluble TfR was isolated from human plasma, and complex formation between sTfR and Tf was studied by stepwise complex construction and by FPLC gel filtration. It was found that sTfR could bind two Tf molecules step by step when the sTfR-Tf complex is constructed in the plate wells. FPLC gel filtration of sTfR-Tf mixtures and analysis of sTfR and sTfR-Tf immunological activities in collected fractions showed that sTfR can form different complexes with TF depending upon the ratios between them: a 291-kDa compound is assumed to be a 2:1 sTfR/Tf complex, and a 345-kDa compound is assumed to be a 2:2 sTfR/Tf complex. Isolated sTfR eluted as a 237-kDa protein. FPLC gel filtration of serum revealed that all sTfR in serum is bound to Tf in a 2:2 complex, and no isolated sTfR can be found in serum. This raises the question as to the nature of the bonds that hold two molecules of sTfR together to form a dimer.

Serum ferritin and transferrin receptor concentrations during the transition from adolescence to adulthood in a healthy Swedish population

AIM

As part of a longitudinal nutrition study of adolescents, changes in serum ferritin (s-Ft), serum transferrin receptors (s-TfR) and the TfR/Ft ratio from 15 to 21 y of age were studied in randomly selected Swedish adolescents.

METHODS

Blood samples from 60 males and 66 females were drawn at 15, 17 and 21 y of age.

RESULTS

In males, median s-Ft increased significantly from 33 microg l(-1) at 15 y to 96 microg l(-1) at 21 y, and in females, after a non-significant decrease at 17 y, from 27 at 15 y to 34 microg l(-1) at 21 y. Between 15 and 17 y, s-TfR increased significantly, in males from 5.9 to 7.7 microg l(-1), and in females from 5.2 to 7.6 microg l(-1), whereas s-TfR decreased significantly in both genders between 17 and 21 y. The log (TfR/Ft) ratio did not change in males between 15 and 17 y, but decreased significantly from 2.2 +/- 0.3 to 1.8 +/- 0.3 by the age of 21 y. In females, the TfR/Ft ratio increased significantly between 15 and 17 y, whereas a significant decrease was found by the age of 21 y. S-Ft <12 microg l(-1) at 15, 17 and 21 y was 3, 2 and 2% in males, and in females 18, 26 and 21%, respectively.

CONCLUSION

This study shows an increase in s-Ft and a decline in s-TfR in males, indicating increased iron stores. In females, s-Ft did not increase significantly, whereas s-TfR and the TfR/Ft ratio decreased between 17 and 21 y, indicating that cellular iron needs were met.

Heme and iron metabolism: role in cerebral hemorrhage

Heme and iron metabolism are of considerable interest and importance in normal brain function as well as in neurodegeneration and neuropathologically following traumatic injury and hemorrhagic stroke. After a cerebral hemorrhage, large numbers of hemoglobin-containing red blood cells are released into the brain's parenchyma and/or subarachnoid space. After hemolysis and the subsequent release of heme from hemoglobin, several pathways are employed to transport and metabolize this heme and its iron moiety to protect the brain from potential oxidative stress. Required for these processes are various extracellular and intracellular transporters and storage proteins, the heme oxygenase isozymes and metabolic proteins with differing localizations in the various brain-cell types. In the past several years, additional new genes and proteins have been discovered that are involved in the transport and metabolism of heme and iron in brain and other tissues. These discoveries may provide new insights into neurodegenerative diseases like Alzheimer's, Parkinson's, and Friedrich's ataxia that are associated with accumulation of iron in specific brain regions or in specific organelles. The present review will examine the uptake and metabolism of heme and iron in the brain and will relate these processes to blood removal and to the potential mechanisms underlying brain injury following cerebral hemorrhage.

Assessing micronutrient status in the presence of inflammation

Measurement of micronutrient status in the presence of inflammation is difficult for several reasons. Changes in levels of acute phase proteins are associated with increased plasma levels of some indicators of micronutrient status, such as ferritin, and decrease of others, such as retinol. Alterations in the plasma levels of acute phase proteins can occur from hemodilution, sequestration and increased or decreased rates of synthesis and breakdown. How much these relate to functional deficiency is not known. Assays that are less perturbed by inflammation, such as the transferrin receptor assay, and adjustment of plasma micronutrient levels according to different cutoff levels for acute phase proteins are helpful but they do not enable precise assessment of micronutrient status among individuals who are infected. Improving assessment of micronutrient status is important if micronutrient interventions are to be targeted to those with the greatest need.

Soluble transferrin receptor and immature reticulocytes are not useful for distinguishing iron-deficiency anemia from heterozygous beta-thalassemia

Iron deficiency and heterozygous beta-thalassemia are important causes of hypochromic-microcytic anemia. Two laboratory parameters are suggested for the differentiation of such anemia. High-fluorescence reticulocyte counts and soluble transferrin receptor levels were determined in iron-deficiency anemia patients (n = 49) and heterozygous beta-thalassemia patients (n = 43). There was no significant difference in high-fluorescence reticulocyte and soluble transferrin receptor values between the two groups, but a correlation was observed between high-fluorescence reticulocytes and soluble transferrin receptors in iron-deficiency anemia, probably due to increased receptor synthesis as a response to decreased iron content in erythrocytes.

Noninvasive measurement of iron: report of an NIDDK workshop

An international workshop on the noninvasive measurement of iron was conducted by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) on April 17, 2001, to assess the current state of the science and to identify areas needing further investigation. The workshop concluded that a clear clinical need is evident for quantitative, noninvasive, safe, accurate, and readily available means of measuring body storage iron to improve the diagnosis and management of patients with iron overload from such disorders as hereditary hemochromatosis, thalassemia major, sickle cell disease, aplastic anemia, and myelodysplasia, among others. Magnetic resonance imaging (MRI) potentially provides the best available technique for examining the 3-dimensional distribution of excess iron in the body, but further research is needed to develop means of making measurements quantitative. Biomagnetic susceptometry provides the only noninvasive method to measure tissue iron stores that has been calibrated, validated, and used in clinical studies, but the complexity, cost, and technical demands of the liquid-helium-cooled superconducting instruments required at present have restricted clinical access to the method. The workshop identified basic and clinical research opportunities for deepening our understanding of the physical properties of iron and iron toxicity, for further investigation of MRI as a method for quantitative determinations of tissue iron, especially in liver, heart and brain, and for development of improved methods and more widely available instrumentation for biomagnetic susceptometry.

Whole blood collected on filter paper provides a minimally invasive method for assessing human transferrin receptor level

Iron deficiency is the most common micronutrient deficiency worldwide, and transferrin receptor (TfR) level has been identified as an important measure of iron status that is not confounded by inflammation. However, logistical constraints associated with sample collection and processing have limited efforts to measure TfR, particularly at the community level. Standardized filter paper provides a relatively convenient and minimally invasive means for collecting and transporting samples of whole blood from simple finger pricks, and we present results of our validation of an improved method for quantifying TfR in dried blood spots. The method is based on commercially available reagents and uses capillary blood that is applied directly from the finger to filter paper, eliminating the need for premeasurement at the collection site. The blood spot TfR assay is precise and reliable, agrees well with plasma TfR, and can be performed at any facility with a microplate reader and basic laboratory equipment. Concentrations of TfR remain stable for at least 4 wk when blood spots are stored at room temperature, but begin to deteriorate after 3 d of exposure to higher temperatures. The advantages and disadvantages of the blood spot TfR method are discussed, as well as its potential contribution to future field-based studies of iron deficiency.

Serum transferrin receptor in the evaluation of the iron status in elderly hospitalized patients with anemia

The aim of the present study is to evaluate in an elderly hospitalized population the diagnostic value of the serum transferrin receptor (sTfR) in distinguishing IDA (iron deficiency anemia) from ACD (anemia of chronic disease) as compared to conventional laboratory tests of iron metabolism, especially serum ferritin. In a prospective study, 34 patients with IDA and 38 patients with ACD (a chronic disorder in 23 and an acute infection in 15) were evaluated using iron status tests including serum transferrin receptor assay. The iron stores were assessed by bone marrow examination. sTfR levels were elevated (>28.1 nmol/L) in 68% of the IDA patients but also in 43% of the patients with ACD-chronic inflammation and 33% with ACD-acute infection. Serum ferritin was the best test to differentiate IDA from ACD patients. We conclude that serum ferritin is a more sensitive and specific parameter than the sTfR assay to predict the bone marrow iron status in an elderly anemic population.

Clinical Consequences of New Insights in the Pathophysiology of Disorders of Iron and Heme Metabolism

This review examines the clinical consequences for the practicing hematologist of remarkable new insights into the pathophysiology of disorders of iron and heme metabolism. The familiar proteins of iron transport and storage—transferrin, transferrin receptor, and ferritin—have recently been joined by a host of newly identified proteins that play critical roles in the molecular management of iron homeostasis. These include the iron-regulatory proteins (IRP-1 and -2), HFE (the product of the HFE gene that is mutated in most patients with hereditary hemochromatosis), the divalent metal transporter (DMT1), transferrin receptor 2, ceruloplasmin, hephaestin, the “Stimulator of Fe Transport” (SFT), frataxin, ferroportin 1 and others. The growing appreciation of the roles of these newly identified proteins has fundamental implications for the clinical understanding and laboratory evaluation of iron metabolism and its alterations with iron deficiency, iron overload, infection, and inflammation.

In Section I, Dr. Brittenham summarizes current concepts of body and cellular iron supply and storage and reviews new means of evaluating the full range of body iron stores including genetic testing for mutations in the HFE gene, measurement of serum ferritin iron, transferrin receptor, reticulocyte hemoglobin content and measurement of tissue iron by computed tomography, magnetic resonance imaging and magnetic susceptometry using superconducting quantum interference device (SQUID) instrumentation.

In Section II, Dr. Weiss discusses the improved understanding of the molecular mechanisms underlying alterations in iron metabolism due to chronic inflammatory disorders. The anemia of chronic disorders remains the most common form of anemia found in hospitalized patients. The network of interactions that link iron metabolism with cellular immune effector functions involving pro- and anti-inflammatory cytokines, acute phase proteins and oxidative stress is described, with an emphasis on the implications for clinical practice.

In Section III, Dr. Brissot and colleagues discuss how the diagnosis and management of hereditary hemochromatosis has changed following the identification of the gene, HFE, that is mutated in most patients with hereditary hemochromatosis, and the subsequent development of a genotypic test. The current understanding of the molecular effects of HFE mutations, the usefulness of genotypic and phenotypic approaches to screening and diagnosis and recommendations for management are summarized.

Clinical Consequences of New Insights in the Pathophysiology of Disorders of Iron and Heme Metabolism

This review examines the clinical consequences for the practicing hematologist of remarkable new insights into the pathophysiology of disorders of iron and heme metabolism. The familiar proteins of iron transport and storage—transferrin, transferrin receptor, and ferritin—have recently been joined by a host of newly identified proteins that play critical roles in the molecular management of iron homeostasis. These include the iron-regulatory proteins (IRP-1 and -2), HFE (the product of the HFE gene that is mutated in most patients with hereditary hemochromatosis), the divalent metal transporter (DMT1), transferrin receptor 2, ceruloplasmin, hephaestin, the “Stimulator of Fe Transport” (SFT), frataxin, ferroportin 1 and others. The growing appreciation of the roles of these newly identified proteins has fundamental implications for the clinical understanding and laboratory evaluation of iron metabolism and its alterations with iron deficiency, iron overload, infection, and inflammation.

In Section I, Dr. Brittenham summarizes current concepts of body and cellular iron supply and storage and reviews new means of evaluating the full range of body iron stores including genetic testing for mutations in the HFE gene, measurement of serum ferritin iron, transferrin receptor, reticulocyte hemoglobin content and measurement of tissue iron by computed tomography, magnetic resonance imaging and magnetic susceptometry using superconducting quantum interference device (SQUID) instrumentation.

In Section II, Dr. Weiss discusses the improved understanding of the molecular mechanisms underlying alterations in iron metabolism due to chronic inflammatory disorders. The anemia of chronic disorders remains the most common form of anemia found in hospitalized patients. The network of interactions that link iron metabolism with cellular immune effector functions involving pro- and anti-inflammatory cytokines, acute phase proteins and oxidative stress is described, with an emphasis on the implications for clinical practice.

In Section III, Dr. Brissot and colleagues discuss how the diagnosis and management of hereditary hemochromatosis has changed following the identification of the gene, HFE, that is mutated in most patients with hereditary hemochromatosis, and the subsequent development of a genotypic test. The current understanding of the molecular effects of HFE mutations, the usefulness of genotypic and phenotypic approaches to screening and diagnosis and recommendations for management are summarized.