Defective iron supply for erythropoiesis and adequate endogenous erythropoietin production in the anemia associated with systemic-onset juvenile chronic arthritis

Systemic-onset juvenile chronic arthritis (SoJCA) is associated with high levels of circulating interleukin-6 (IL-6) and is frequently complicated by severe microcytic anemia whose pathogenesis is unclear. Therefore, we studied 20 consecutive SoJCA patients with hemoglobin (Hb) levels <12 g/dL, evaluating erythroid progenitor proliferation, endogenous erythropoietin production, body iron status, and iron supply for erythropoiesis. Hb concentrations ranged from 6.5 to 11.9 g/dL. Hb level was directly related to mean corpuscular volume (r = .82, P < .001) and inversely related to circulating transferrin receptor (r = - .81, P < .001) suggesting that the severity of anemia was directly proportional to the degree of iron-deficient erythropoiesis. Serum ferritin ranged from 18 to 1,660 microgram/L and was unrelated to Hb level. Bone marrow iron stores wore markedly reduced in the three children investigated, and they also showed increased serum transferrin receptor and normal-to-high serum ferritin. All 20 patients had elevated IL-6 levels and normal in vitro growth of erythroid progenitors. Endogenous erythropoietin (epo) production was appropriate for the degree of anemia as judged by both the observed to predicted log (serum epo) ratio 10.95 +/- 0.12) and a comparison of the serum epo- Hb regression found in these subjects with that of thalassemia patients. Multiple regression analysis showed that serum transferrin receptor was the parameter most closely related to hemoglobin concentration: variation in circulating transferrin receptor explained 61% of the variation in Hb level (P < .001). In 10 severely anemic patients, amelioration of anemia following intravenous iron administration resulted in normalization of serum transferrin receptor. Defective iron supply to the erythron rather than blunted epo production is the major cause of the microcytic anemia associated with SoJCA. A true body-iron deficiency caused by decreased iron absorption likely complicates long-lasting inflammation in the most anemic children, and this can be recognized by high serum transferrin receptor levels. Although oral iron is of no benefit, intravenous iron saccharate is a safe and effective means for improving iron availability for erythropoiesis and correcting this anemia. Thus, while chronically high endogenous IL-6 levels do not appear to blunt epo production, they are probably responsible for the observed abnormalities in iron metabolism. Anemia of chronic disease encompasses a variety of anemic conditions whose peculiar features may specifically correlate with the type of cytokine(s) predominantly released.     

Factor V Leiden mutation carriership and venous thromboembolism in polycythemia vera and essential thrombocythemia

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.     

Ret-Y a measure of reticulocyte size: a sensitive indicator of iron deficiency anemia

In this study the size of reticulocytes was measured, reticulocyte-Y (Ret-Y), to distinguish iron deficiency anemia from the anemia of chronic disease using a Sysmex XE2100 cell counter. We evaluated this parameter prospectively in 100 patients seen for the evaluation of anemia. A clinical diagnosis of iron deficiency anemia or anemia of chronic disease was made on the basis of a complete blood count, examination of the peripheral smear, and serum ferritin along with a history and physical examination. We analyzed the sensitivity and specificity of the Ret-Y in relationship to the clinical diagnosis. We also measured serum transferrin receptor levels to use as the gold standard laboratory test for iron deficiency against which we compared the Ret-Y. In 40 normal individuals with normal serum ferritin and transferrin receptor levels the mean Ret-Y was 1874 +/- 178 (1 SD). The mean Ret-Y in the anemia of chronic disease group (n=62) was 1722 +/- 162, not significantly different from normal. The mean Ret-Y value among iron-deficient patients (n=38), was 1407 +/- 136 (P <0.01 vs. the anemia of chronic disease group's Ret-Y value). Receiver operator curves showed that Ret-Y correlated closely to the serum transferrin receptor and was superior to the mean corpuscular volume, and ferritin level, in differentiating the type of anemia. The Ret-Y parameter has the highest overall sensitivity and specificity of the panel of tests routinely used in differentiating iron deficiency anemia from anemia of chronic disease.     

Ret‐Y a measure of reticulocyte size: a sensitive indicator of iron deficiency anemia

In this study the size of reticulocytes was measured, reticulocyte‐Y (Ret‐Y), to distinguish iron deficiency anemia from the anemia of chronic disease using a Sysmex XE2100 cell counter. We evaluated this parameter prospectively in 100 patients seen for the evaluation of anemia. A clinical diagnosis of iron deficiency anemia or anemia of chronic disease was made on the basis of a complete blood count, examination of the peripheral smear, and serum ferritin along with a history and physical examination. We analyzed the sensitivity and specificity of the Ret‐Y in relationship to the clinical diagnosis. We also measured serum transferrin receptor levels to use as the gold standard laboratory test for iron deficiency against which we compared the Ret‐Y. In 40 normal individuals with normal serum ferritin and transferrin receptor levels the mean Ret‐Y was 1874 ± 178 (1 SD). The mean Ret‐Y in the anemia of chronic disease group (n = 62) was 1722 ± 162, not significantly different from normal. The mean Ret‐Y value among iron‐deficient patients (n = 38), was 1407 ± 136 (P < 0.01 vs. the anemia of chronic disease group's Ret‐Y value). Receiver operator curves showed that Ret‐Y correlated closely to the serum transferrin receptor and was superior to the mean corpuscular volume, and ferritin level, in differentiating the type of anemia. The Ret‐Y parameter has the highest overall sensitivity and specificity of the panel of tests routinely used in differentiating iron deficiency anemia from anemia of chronic disease.     

Serum transferrin receptor as a new index of erythropoiesis

Serum transferrin receptors were measured by a sandwich radioimmunoassay procedure in patients with iron deficiency anemia, autoimmune hemolytic anemia and aplastic anemia. The mean circulating transferrin receptor concentration of normal subjects and patients with iron deficiency anemia, autoimmune hemolytic anemia and aplastic anemia are 253 +/- 82 ng/mL, 730 +/- 391 ng/mL, 1,426 +/- 1,079 ng/mL, and 182 +/- 39 ng/mL, respectively. The values for those with iron deficiency anemia and autoimmune hemolytic anemia were significantly higher than that of normal controls and the values for those with aplastic anemia were lower than that of normal controls. After iron supplementation in iron deficiency anemia, the serum transferrin receptor values increased twofold over those of pretreatment values. This increase parallels an increase in peripheral reticulocytes. Therefore, the number of circulating transferrin receptors in anemic patients may reflect the level of bone marrow erythropoiesis and is a potentially useful new index for red cell production.     

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.     

Diagnosis of iron deficiency anemia in the elderly by transferrin receptor-ferritin index

BACKGROUND: The diagnosis of iron deficiency anemia (IDA) in the elderly is difficult because of the prevalence of chronic diseases, which can cause anemia with high ferritin levels, even in the presence of iron deficiency. Therefore, we studied the sensitivity and specificity of a serum transferrin receptor assay, which is not affected by chronic diseases, in the diagnosis of IDA in elderly patients. METHODS: We performed a prospective controlled study of 49 consecutive male and female patients older than 80 years who were admitted to an acute geriatric department. Bone marrow aspirate confirmed IDA in all 49 patients. Fourteen additional patients, also older than 80 years, with anemia but without evidence of iron deficiency on results of bone marrow examination, served as a control group. All patients underwent evaluation by means of a detailed medical history and results of complete physical examination, routine blood tests, and specific tests for diagnosis and evaluation of anemia. Examination of bone marrow aspirate was performed for all patients. Levels of transferrin receptor in serum were determined by means of a specific enzyme-linked immunosorbent assay. The transferrin receptor-ferritin index (TR-F index) was defined as the ratio of serum transferrin receptor level to log ferritin level. RESULTS: Only 8 patients could be diagnosed as having IDA by means of routine blood test results (serum iron, ferritin, and transferrin saturation levels). In contrast, the TR-F index disclosed IDA in 43 of the 49 patients, thus increasing the sensitivity from 16% to 88%. CONCLUSIONS: The diagnosis of IDA in the elderly by means of routine blood tests has a very low sensitivity. The TR-F index is much more sensitive, and when results are positive, the TR-F index can eliminate the need for bone marrow examination.     

Soluble transferrin receptor and soluble transferrin receptor/log ferritin index in diagnosis of iron deficiency anemia in pediatric inflammatory bowel disease

Background

There is no single reliable marker of iron homeostasis in inflammatory bowel disease.

贫血患者血清转铁蛋白受体测定的临床意义

采用Ｄｏｔ－ＥＬＩＳＡ法定量测定了６８例不同贫血患者的血清转铁蛋白受体（ｓＴＩＲ）水平,发现缺铁性贫血,溶血性贫血和急性失血性贫血患者ｓＴＩＲ均显高于正常人（Ｐ〈０．００１）,而慢性再生障碍性贫血患者ｓＴｆＲ显著低于正常人（Ｐ〈０．００１）,缺铁性贫血ｓＴｆＲ水平与血清铁蛋白水平呈负相关（Ｐ〈０．００５）,溶血性贫血ｓＴｆＲ与网织红细胞计数呈正相关（Ｐ〈０．００５）,ｓＴｆＲ可以反映机体贮存铁和骨     

Serum transferrin receptor

Transferrin receptors (TfRs) are the conventional pathway by which cells acquire iron for physiological requirements. Under iron-deficient conditions there is an increased concentration of surface TfR, especially on bone marrow erythroid precursors, as a mechanism to sequester needed iron. TfRs are also present in the circulation, and the circulating serum TfR (sTfR) level reflects total body TfR concentration. Under normal conditions erythroid precursors are the main source of sTfR. Disorders of the bone marrow with reduced erythroid precursors are associated with low sTfR levels. The sTfR concentration begins to rise early in iron deficiency with the onset of iron-deficient erythropoiesis, and continues to rise as iron-deficient erythropoiesis progressively worsens, prior to the development of anemia. The sTfR level does not increase in anemia of chronic inflammation, but is increased when anemia of chronic inflammation is combined with iron deficiency. The sTfR level is also increased in patients with expanded erythropoiesis, including hemolytic anemias, myelodysplastic syndromes, and use of erythropoietic stimulating agents. The ratio of sTfR/ferritin can be used to quantify the entire spectrum of iron status from positive iron stores through negative iron balance, and is particularly useful in evaluating iron status in population studies. The sTfR/log ferritin ratio is valuable for distinguishing anemia of chronic inflammation from iron deficiency anemia, whether the latter occurs alone or in combination with anemia of chronic inflammation.     

Clinical evaluation of iron deficiency

While the prevalence of iron deficiency has remained relatively constant, there has been continuing refinement in its laboratory recognition, especially with the recent introduction of serum ferritin and FEP measurements. It is helpful to classify iron deficiency into three stages. Storage iron depletion is identified by marrow examination or serum ferritin, iron deficient erythropoiesis by TS, FEP, or MCV, and iron deficiency anemia by hemoglobin concentration or therapeutic iron trial. Combinations of these measurements have been used in prevalence studies to obtain a quantitative measure of body iron stores. The optimal laboratory approach to diagnosing iron deficiency depends on the clinical setting. In the office or outpatient clinic, iron depletion is best recognized by the serum ferritin, although the TS, FEP, and MCV are helpful in gauging its severity. In hospitalized patients with overt anemia, the TS, FEP, and MCV are much less helpful because similar changes are seen in the anemia of chronic disease. Examination of marrow iron remains the method of choice, especially in patients with infection, chronic disease, malignancy, or liver disease, although in many clinical situations the same information can be obtained from a serum ferritin. Serial measurements of serum ferritin have been particularly useful in monitoring patients at high risk of iron deficiency such as those with rheumatoid arthritis, chronic inflammatory bowel disease, or chronic renal failure.     

Diagnosis and management of iron-deficiency anaemia

Anaemia is typically the first clue to iron deficiency, but an isolated haemoglobin measurement has both low specificity and low sensitivity. The latter can be improved by including measures of iron-deficient erythropoiesis such as the transferrin iron saturation, mean corpuscular haemoglobin concentration, erythrocyte zinc protoporphyrin, percentage of hypochromic erythrocytes or reticulocyte haemoglobin concentration. However, the changes in these measurements with iron deficiency are indistinguishable from those seen in patients with the anaemia of chronic disease. The optimal diagnostic approach is to measure the serum ferritin as an index of iron stores and the serum transferrin receptor as a index of tissue iron deficiency. The treatment of iron deficiency should always be initiated with oral iron. When this fails because of large blood losses, iron malabsorption, or intolerance to oral iron, parenteral iron can be given using iron dextran, iron gluconate or iron sucrose.     

Iron deficiency in inflammatory bowel disease

The prevalence of iron-deficiency anemia was defined in 105 patients with inflammatory bowel disease and an appraisal made of the diagnostic value of serum ferritin for the assessment of iron stores. Iron deficiency, defined by the absence of bone-marrow hemosiderin was found with anemia in 36% of 41 patients with ulcerative colitis (UC) and 22% of 64 patients with Crohn's disease (CD). Iron deficiency without impaired erythropoiesis was detected in an additional 32% of patients with UC and 2% with CD. Anemia with plentiful bone-marrow iron was present in 33 (51%) of patients with CD, only one of whom had vitamin B₁₂ deficiency. Red blood cell morphology, RBC indices, serum iron, and percent transferrin saturation correlated poorly with stainable marrow iron. Serum ferritin, assayed in samples from 45 patients, was <18 ng/ml in 4/12 with iron-deficiency anemia and 0/5 with absent marrow iron and a normal hemoglobin level; values >55 ng/ml were invariably associated with the presence of marrow hemosiderin. Based on a lower normal limit of 18 ng/ml, the serum ferritin had an excellent predictive value (100%) but a high predictive error (32%) in the diagnosis of iron deficiency in inflammatory bowel disease. Serum ferritin >55 ng/ml ruled out iron deficiency as the basis for anemia.     

Serum soluble transferrin receptor in the diagnosis of iron deficiency in chronic liver disease

Fifty-one consecutive patients with chronic liver disease (CLD) underwent investigations of their iron status (full blood count, serum iron [Fe], total iron binding capacity [TIBC], transferrin saturation [TS], serum ferritin and serum soluble transferrin receptor [sTfR] level). Twenty-six patients were anaemic; 12 patients had iron deficiency, and 10 had iron deficiency anaemia (IDA). The median (range) sTfR in the IDA patients was 16.6 (11.2–24.8) mg/l, compared with 6.6 mg/l (11.2–24.8) in the 16 patients with anaemia due to other causes (P = 0.01). The sensitivity of sTfR for diagnosing iron deficiency in CLD was 91.6% (100% if only anaemic patients are included) and the specificity was 84.6%. Patients with haemolysis and recent blood loss may have falsely elevated sTfR levels. The results suggest that the sTfR is as useful as serum ferritin in identifying a potentially treatable cause of anaemia in CLD.     

Serum soluble transferrin receptor in the diagnosis of iron deficiency in chronic liver disease.

Fifty-one consecutive patients with chronic liver disease (CLD) underwent investigations of their iron status (full blood count, serum iron [Fe], total iron binding capacity [TIBC], transferrin saturation [TS], serum ferritin and serum soluble transferrin receptor [sTfR] level). Twenty-six patients were anaemic; 12 patients had iron deficiency, and 10 had iron deficiency anaemia (IDA). The median (range) sTfR in the IDA patients was 16.6 (11.2-24.8) mg/l. compared with 6.6 mg/l (11.2-24.8) in the 16 patients with anaemia due to other causes (P = 0.01). The sensitivity of sTfR for diagnosing iron deficiency in CLD was 91.6% (100% if only anaemic patients are included) and the specificity was 84.6%. Patients with haemolysis and recent blood loss may have falsely elevated sTfR levels. The results suggest that the sTfR is as useful as serum ferritin in identifying a potentially treatable cause of anaemia in CLD.     

Reticulocyte hemoglobin content (MCHr) in the assessment of iron deficient erythropoiesis in inflammatory bowel disease

BackgroundIn conditions associated with inflammation, biochemical parameters alone could be inadequate for assessing iron status. We investigated the potential utility of mean reticulocyte hemoglobin content (MCHr) in the assessment of the erythropoiesis status in inflammatory bowel disease (IBD).MethodsWe recruited 124 anemic outpatients with IBD. Serum iron, transferrin and ferritin were tested. Complete blood counts were performed on a CELL-DYN Sapphire analyzer (Abbott Diagnostics).Differences among groups were assessed using analysis of variance, considering P < 0.05 to be significant.Receiver operating characteristic analysis was used to assess the diagnostic performance of MCHr for detecting iron deficient erythropoiesis.The reference used as an indicator of insufficient iron availability was transferrin saturation <20%.ResultsOverall, 47.6% of the patients had iron deficiency anemia (IDA) and 31.5% anemia of chronic disease (ACD), while the others (20.9%) had mixed anemia.Patients with ACD or mixed anemia showed functional iron deficiency: normal or high ferritin and low MCHr. The area under curve was 0.858 (95% CI 0.742–0.942), considering a cut off 30.3 pg, the sensitivity was 82.2%, specificity 83.3%.ConclusionsMCHr provides information on iron availability in IBD patients. It is a reliable test to assess iron supply for erythropoiesis.     

The diagnosis of iron deficiency anemia in sickle cell disease

We determined the prevalence and optimal methods for laboratory diagnosis of iron deficiency anemia in patients with sickle cell disease. Laboratory investigations of 38 nontransfused and 32 transfused patients included transferrin saturation, serum ferritin, mean corpuscular volume (MCV), and free erythrocyte protoporphyrin (FEP). Response to iron supplementation confirmed the diagnosis of iron deficiency anemia in 16% of the nontransfused patients. None of the transfused patients were iron deficient. All iron-deficient patients (mean age 2.4 yr) had a low MCV, serum ferritin less than 25 ng/ml, transferrin saturation less than 15%, and FEP less than 90 micrograms/dl RBC. Following therapy, all parameters improved and the hemoglobin concentration increased greater than 2 g/dl. A serum ferritin below 25 ng/ml was the most reliable screening test for iron deficiency. There were 13% false positive results with transferrin saturation, 3% with MCV, and 62% with FEP. FEP values correlated strongly with reticulocyte counts. The high FEP was in part due to protoporphyrin IX and not completely due to zinc protoporphyrin, which is elevated in iron deficiency. We conclude that iron deficiency anemia is a potential problem in young nontransfused sickle cell patients. Serum ferritin below 25 ng/ml and low MCV are the most useful screening tests.     

Assessment of iron stores in anemic geriatric patients

Of patients referred to a geriatric service, 66 were identified who were clearly anemic (hemoglobin less than 12 g in men, less than 11 g in women) but whose cause of anemia was not readily identifiable by noninvasive measures. The difficulty in distinguishing iron deficiency from chronic disease as a cause of anemia by noninvasive means (serum iron, total iron binding capacity, transferrin saturation ratio, and serum ferritin), is highlighted by the poor power of these investigations when compared with bone marrow iron stores. A transferrin saturation ratio of less than 11% and a serum ferritin of less than 45 pg/L serve better than currently accepted values to identify iron deficiency in this population.     

Serum transferrin receptor in the megaloblastic anemia of cobalamin deficiency.

In order to further study the relation between transferrin receptor and erythropoiesis we examined serum receptor levels in megaloblastic anemia, which is the classic example of ineffective erythropoiesis. We studied 33 patients with unequivocal cobalamin deficiency, only 22 of whom were anemic. High serum transferrin receptor levels were found in 12 patients, all of whom were anemic and had high lactate dehydrogenase (LDH) levels; in contrast, only 10 of the 21 patients with normal receptor levels were anemic. Receptor correlated most strongly with LDH (r = 0.573, p < 0.001) and, inversely, with hemoglobin values (r = -0.560, p < 0.001); it also correlated with ferritin and total bilirubin levels, but not with cobalamin, MCV or erythropoietin. No association was found with the hemolytic component of megaloblastic anemia, represented indirectly by haptoglobin levels. Changes induced by cobalamin therapy were also examined in 13 patients. Transferrin receptors rose in all 6 patients who initially had high levels and in 2 of 3 patients who had borderline levels, but not in the 4 patients with initially normal levels. The receptor levels began to rise within 1-3 days, peaked at about 2 weeks and returned to normal at about the 5th wk. The findings indicate that serum transferrin receptor levels reflect the severity of the megaloblastic anemia. The elevated receptor levels rise further with cobalamin therapy, however, as effective erythropoiesis replaces ineffective erythropoiesis, and these persist until the increased erythropoiesis returns to normal.