Red blood cell distribution width index in some hematologic diseases

The red blood cell distribution width index (RDW) was determined in a group of anemic male patients and normal male blood donors. Elevated mean RDW values were found in the anemic patients, with the highest value seen in sickle cell anemia, sickle cell-beta thalassemia, sickle cell trait, beta-thalassemia trait, and iron deficiency in decreasing order of magnitude. The mean RDW of the normal male subjects was 11.3. It was found that the RDW was proportional to the reticulocyte count, with the highest values in the patients with the highest reticulocyte count (sickle cell anemia). One clinical value of the RDW therefore may lie in its capacity for reflecting active erythropoiesis. For example, patients with normal or near-normal hemoglobin and with high RDWs may be suspected of having an elevated reticulocyte count that may indicate a hemoglobinopathy, such as sickle cell trait or thalassemia trait.     

Clinical significance of red cell distribution width in polycythemia vera

We evaluated changes in red cell distribution width-standard deviation (RDW-SD) measured using a multiple parameter automated hematology analyzer E 4000 in patients with polycythemia vera (PV). Patients with iron deficiency anemia, those with chronic myelogenous leukemia, those with primary thrombocythemia, and normal subjects were examined as controls. In the patients with PV, as in those with the other 3 diseases, RDW-SD tended to be higher than in the normal controls when red blood cell counts were high. The RDW-SD in patients with PV transiently increased following administration of a myelosuppressive, which corresponded to the transition period from microcytes to normal blood cells. It was even higher during the polycythemic period than during the myelofibrotic period. This may be associated with hematopoietic abnormality due to extramedullary hematopoiesis. RDW-SD seems to well reflect the pathologic status of PV.     

Usefulness of cell counter-based parameters and formulas in detection of beta-thalassemia trait in areas of high prevalence

The present study aimed to retrospectively evaluate the usefulness of cell counter-based parameters and formulas in beta-thalassemia trait (BTT) detection. The study included 170 BTT cases (hemoglobin [Hb]A(2) >4.0% [0.04]) and 30 non-BTT cases (HbA(2), 2.3%-3.5% [0.02-0.04]). Depending on the hemoglobin level and iron deficiency, the BTT group was further classified into classic BTT (n = 112) and BTT with iron deficiency anemia (n = 58). The RBC count, MCH, MCV, RDW, and Shine and Lal, Mentzler, Srivastava, England and Fraser, Ricerca, and Green indexes were applied. For the first time in the population of India, these 10 cell counter parameters and manual formulas were compared with high-performance liquid chromatography-derived HbA2 levels for deriving a cost-effective alternative method; and receiver operating characteristic curves were applied. We found that the Shine and Lal, Srivastava, and Mentzler indexes, MCV, and MCH have better discriminative function than the RBC count and red cell distribution width and their related formulas.     

Automated measurement of red blood cell microcytosis and hypochromia in iron deficiency and beta-thalassemia trait.

Some routine red blood cell (RBC) measurements and indexes (count, mean volume, volume dispersion, and mean hemoglobin [HGB] concentration) can be used to differentiate iron deficiency from heterozygous beta-thalassemia. A number of formulas that incorporate two or more of these measurements have been described to amplify such differences. The H*1 hematology analyzer directly measures volume and HGB concentration of individual RBCs. We have assessed the diagnostic usefulness of conventional and new RBC measurements provided by the H*1 on a learning data set that comprised 119 patients with iron deficiency and 172 patients with beta-thalassemia trait, both untreated and uncomplicated. The most striking finding was the inverse behavior of percentages of microcytes (volume, less than 60 fL) and hypochromic RBCs (HGB concentration, less than 280 g/L) in the two conditions. In 162 of 172 patients with beta-thalassemia trait, the percentage of microcytes (mean, 33.1%; central 95th percentile range, 9.2% to 54.5%) was higher than the percentage of hypochromic RBCs (mean, 13.9%; central 95th percentile range, 1.7% to 24.7%). In 105 of 119 patients with iron deficiency, on the contrary, the percentage of hypochromic cells (mean, 34.6%; central 95th percentile range, 9.7% to 73.1%) was higher than the percentage of microcytes (mean, 12.8%; central 95th percentile range, 1.7% to 29.6%). The ratio between the percentage of microcytes and the percentage of hypochromic cells provided by the H*1 (microcytic-hypochromic ratio) was useful in differentiating the two types of microcytic anemia: with the use of a discriminant value of 0.9, the discriminant efficiency of the microcytic-hypochromic ratio was 92.4% (95% confidence interval, 88.8% to 95.2%), higher than that of the five previously described discriminant formulas and simple RBC measurements. When assessed on a test data set that comprised 149 unselected cases of microcytic anemia, a microcytic-hypochromic ratio lower than 0.9 demonstrated high sensitivity (94.0%), specificity (92.3%), and predictive value (94.0%) for the presence of iron-deficient erythropoiesis in patients with isolated iron deficiency, polycythemia vera treated by phlebotomy, and iron deficiency complicating heterozygous thalassemia. In conclusion, our results showed that iron-deficient erythropoiesis is characterized by the production of RBCs with a severely decreased HGB concentration, while microcytes of beta-thalassemia trait are generally smaller, with a more preserved HGB concentration. Such properties, as assessed by the H*1 hematology analyzer, are very useful in distinguishing these two common types of microcytic anemia.     

Spectrum of anemia in pregnant Indian women and importance of antenatal screening

Anemia is a common health problem but control of anemia in pregnant women is less well studied. The purpose was to study prevalence of anemia in young pregnant women, correlate with indices and study significance of identification of hemoglobinopathies. Of the 120 pregnant women, Hb was less than 8 g% in 58 (44.2%). Seventy-eight (65%) had iron deficiency, 22 (18.3%) had dimorphic anemia, and 14 (11.6%) had hemolytic anemia. Megaloblastic anemia was present in 6 (5%). Of hemolytic anemia, 50% were thalassemia trait. MCV< 76 fl was observed in 88 (73.3 %) cases. MCV<76 fl and MCH < 27 pg had 100 % sensitivity and 28.7 % specificity for screening of beta-thalassemia trait. NESTROFT had comparable sensitivity but lower specificity (14.9%). Sixty-three percent (60/78) of IDA had increased RDW whereas 78 % (11/14) of hemolytic anemia had RDW value in normal range (p value< 0.05). MCV/RBC of <14 was more specific parameter (96.8%) for beta-thalassemia trait. Four high-risk couples were identified. Thus, moderate to severe anemia was observed in most pregnant women. Hemoglobinopathies should be screened in antenatal clinics to identify the couples that would need a prenatal test. A lower MCV/RBC with RDWin the normal range may be useful in screening for thalassemia trait in pregnant women.     

Discrimination between iron deficiency and heterozygous beta-thalassemia in children

The authors studied 119 children with microcytic anemia who were selected by lack of response to a month's treatment with oral iron. Family studies and retesting after further treatment with iron were done in all cases to ensure accurate diagnosis. Seventy-five cases of beta-thalassemia minor (BTM) and 40 cases of iron deficiency were identified. In all 75 cases of BTM, at least one parent had a mean cell volume (MCV) less than 79 microns. In 35 of 40 children with iron deficiency, the MCV of both parents was normal. In contrast, Hb A2 was normal in 15% (11 of 75) of children with BTM, until they received additional treatment with oral iron. The authors conclude that in children with microcytic anemia unresponsive to a month's treatment with oral iron, the MCV of the parents is superior to Hb A2 in discriminating between iron deficiency and heterozygous beta-thalassemia. Repeated testing after additional treatment with oral iron may be needed to ensure accurate diagnosis.     

Usefulness of certain red blood cell indices in diagnosing and differentiating thalassemia trait from iron-deficiency anemia

Iron-deficiency anemia and thalassemia are among the most common microcytic anemias. Differentiating these anemias by means of hemogrant indices is imprecise. Powerful statistical computer programming now enables sensitive discriminant analyses to aid in the diagnosis. Laboratory results from 383 adults were examined retrospectively and grouped according to their original diagnoses: normal (n = 78); beta-thalassemia (n = 134); alpha-thalassemia (n = 106); and iron-deficiency anemia (n = 65). Statistical analysis of results evaluated only RBC indices: RBC count, hemoglobin level, mean corpuscular volume, mean corpuscular hemoglobin, and RBC distribution width. Stepwise multivariate discriminant analysis determined those indices that best differentiated the 4 groups. The Fisher linear discriminant function for each group was calculated and tested casewise. Discriminant analysis identified mean corpuscular hemoglobin, RBC count, mean corpuscular volume, and RBC distribution width as the best set of indices for differentiating the 4 diagnoses. Casewise testing of the calculated Fisher linear discriminant function resulted in mean-weighted sensitivity of 80.4%. The present study demonstrates that a set of linear discriminant functions based on routine hemogram data can effectively differentiate between alpha-thalassemia, beta-thalassemia, and iron-deficiency anemia, with a high degree of accuracy.     

New parameters in erythrocyte counting. Value of histograms

In this report we rate a new, third-generation automated hematology system (Technicon Instruments H-1) that can furnish a full range of values, including erythrocyte parameters and a leukocyte differential count. Particular attention is focused on erythrocyte morphometric parameters, including measurement of cell size and hemoglobin content on a cell-by-cell basis. We assess the usefulness of new parameters derived from these measurements, such as mean corpuscular volume and red blood cell distribution width, which characterize cell size, and mean corpuscular hemoglobin concentration, and hemoglobin distribution width, which characterize cell hemoglobinization in evaluating normal and abnormal subjects. The value of these parameters in classifying anemias is assessed in our patient population that includes those with iron deficiency anemias and thalassemias, as well as other forms of anemia.     

Chromatographic measurements of hemoglobin A2 in blood samples that contain sickle hemoglobin

In the sickle cell syndromes, Hb A2 measurements aid in the differential diagnosis of sickle cell anemia from sickle-beta-thalassemia. The purpose of this study is to assess the Hb A2 levels in samples containing sickle hemoglobin (Hb S) by the use of an automated high performance liquid chromatography system (HPLC-Variant beta-thalassemia Short Program). The blood samples analyzed were from individuals of African descent living in the state of Tennessee who had either sickle cell trait (Hb AS), sickle cell disease (Hb SS), or sickle cell-hemoglobin C disease (Hb SC). Interestingly, the Hb A2 levels determined by HPLC were found elevated in samples containing Hb S. The Hb A2 mean in Hb AS samples (n=146) is 4.09% (SD +/- 0.42, range 2.20 to 5.20%); in Hb SS samples (n=33) it is 3.90% (SD +/- 1.08, range 0.60 to 5.90%); and in Hb SC samples (n=27) it is 4.46% (SD +/- 0.70, range 2.30 to 5.91%). The Hb A2 mean by HPLC in normal individuals (Hb AA, n=70) is 2.57% (SD +/- 0.25, range 2.1 to 3.0%), and the Hb A2 range in beta-thalassemia carriers is 4 to 9%. Our results show that the Hb A2 levels in Hb S-containing samples partially overlap with those expected from beta-thalassemia carriers. The hemoglobinopathy laboratory should be aware of this apparent elevation in Hb A2 levels determined by HPLC in individuals carrying Hb S. Other factors, such as family history and clinical symptoms, should be taken into account before a diagnosis of sickle cell trait, sickle-beta-thalassemia, or sickle cell anemia is made.     

Efficiency of premarital screening of beta-thalassemia trait using MCH rather than MCV in the population of Fars Province,Iran

Iran is a country with high prevalence of about 5-10% of beta-thalassemia trait. The prevalence of Cooly's anemia has declined from 11.6 in 10000 population to 7.2 in 10000 in a five-year period due to screening program of beta-thalassemia trait before marriage. This study was conducted to compare the sensitivity of mean corpuscular hemoglobin (MCH) < 27 pg and mean corpuscular volume (MCV) < 80 fl as a screening test in first step of screening of beta-thalassemia trait. From 2449 couples (4898 cases) participating in the premarital screening to our clinic, 902 cases with either MCH < 27 pg, MCV < 80 fl, anemia, pallor or family history of beta-thalassemia were enrolled in the study. MCV, MCH as well as Hb A2 were measured in all cases. MCH and MCV had sensitivities of 98.5% and 97.6% for the diagnosis of beta-thalassemia trait, respectively. A false negative value of MCH is about 1% lower than that of MCV. MCH is a more sensitive screening test for detecting beta-thalassemia minor before marriage.     

Flow cytometric measurement of hemoglobin F in RBCs: diagnostic usefulness in the distinction of hereditary persistence of fetal hemoglobin (HPFH) and hemoglobin S-hPFH from other conditions with elevated levels of hemoglobin F

The cellular distribution of hemoglobin F is important for evaluating persistently elevated hemoglobin F levels, such as in hereditary persistence of fetal hemoglobin (HPFH) or delta/beta-thalassemia, and for differentiating homozygous hemoglobin S (or hemoglobin S-beta(0)-thalassemia) from hemoglobin S-HPFH, traditionally done by using the Kleihauer-Betke (K-B) acid elution test. We evaluated a flow cytometric method using an anti-hemoglobin F antibody as a replacement for the K-B test. We used 172 specimens representing a variety of conditions: HPFH trait, 19 cases; delta/beta-thalassemia trait, 8 cases; hemoglobin S-HPFH, 10 cases. By flow cytometry, all cases of HPFH trait gave a hemoglobin F pattern comparable to the homocellular pattern obtained by the K-B test; all cases of delta/beta-thalassemia tested gave a pattern comparable to a K-B heterocellular pattern. Most cases of hemoglobin S-HPFH gave a homocellular distribution of hemoglobin F whereas all cases of homozygous hemoglobin S with elevated hemoglobin F levels gave a heterocellular pattern. Flow cytometry provides a more rapid and objective method for assessing cellular distribution of hemoglobin F and is useful for patient evaluation when HPFH trait, delta/beta-thalassemia trait, or hemoglobin S-HPFH trait is suspected.     

The role of HFE mutations on iron metabolism in beta-thalassemia carriers

Hereditary hemochromatosis (HH) is an autosomal recessive disorder of iron metabolism characterized by increased iron absorption and progressive storage resulting in organ damage. HFE gene mutations C282Y and H63D are responsible for the majority of HH cases. A third HFE mutation, S65C, has been associated with the development of a mild form of hemochromatosis. The beta-thalassemia trait is characterized by mild, ineffective erythropoiesis that can induce excess iron absorption and ultimately lead to iron overload. The aim of this study was to evaluate the effect of genetic markers (HFE mutations C282Y, H63D, and S65C) on the iron status of beta-thalassemia carriers. A total of 101 individuals heterozygous for beta-thalassemia and 101 normal control individuals were studied. The allelic frequencies of C282Y (1.5 versus 3.5%), H63D (15.3 versus 18.3%), and S65C (1.0 versus 1.5%) did not differ significantly between beta-thalassemia carriers and normal controls. Serum iron (P=0.029) and transferrin saturation (P=0.009) were increased in beta-thalassemia carriers heterozygous for H63D mutation. The number of subjects carrying C282Y or S65C mutations was too low to conclude their effect on the iron status. These results suggest that the beta-thalassemia trait tends to be aggravated with the coinheritance of H63D mutation, even when present in heterozygosity.     

Transferrine soluble receptors' contribution to the assessment of iron status in homozygous drepanocytic anemia

Sickle cell anemia does not cause martial deprivation per se, but may worsen when iron deficiency exists, notably in tropical zone where infectious diseases and malnutrition are endemic mainly during childhood. This study was aimed to assess iron deficiency prevalence among children with sickle cell disease (SCD) and to determine the best parameters for its diagnosis. In addition to classical parameters, we measured transferrine's soluble receptors which can reveal an iron deficiency, either isolated or associated to another condition since its level is not influenced by chronic anemia. Assays were carried out in 40 homozygous SCD patients, aged 3 to 18 years, having an hemoglobin level < 11 g/dL and in 30 age-paired controls assumed to be healthy and having a negative Emmel test and an hemoglobin level < 11 g/dL. The results showed hyposideremia (serum iron < 60 microg/dL) in 17.5% of the patients. Ferritinemia, transferrinemia as well as total iron fixation capacity were in the normal range for the majority of SCD patients in spite of the frequency of hyposideremia and microcytic anemia (20%). Transferrine's saturation coefficient was low in 22.5% of patients, which can be due to martial deprivation or to inflammatory status. These results confirm the limitations of usual biochemical parameters in the diagnosis of iron deficiency in homozygous drepanocytosis. Soluble receptors' levels were increased in 60% of controls; that proves that iron deficiency prevalence is high in our countries. Higher levels were found in 97.5% of patients. However, receptors' levels are increased during haemolysis, thus it is difficult to ascertain the origin of the increase, but taking into account its index value can reduces misinterpretation. In addition, considering simultaneously microcytosis, hypochromia, transferrine's soluble receptor level and its index, we can speculate that martial deficiency occurs in 20% of SCD patients, a percentage close to the 17.1% obtained by other authors using only the combination of microcytosis and hypochromia. It results from this study that associating microcytosis and hypochromia could validly assess iron deficiency during drepanocytosis.     

Limitations of red blood cell distribution width (RDW) in evaluation of microcytosis

The red blood cell distribution width (RDW) has been proposed as an additional variable that would improve the initial classification of anemia. Microcytic anemias with an elevated RDW (greater heterogeneity) were used to distinguish iron deficiency from heterozygous thalassemia, which was said to have a normal RDW (more homogeneous). The authors attempted to classify their population of microcytic cases using the RDW as a major variable, but found only limited utility. While most of the iron-deficient cases had an increased RDW, almost one-half of the thalassemia cases also were classified as microcytic heterogeneous (increased RDW). The authors also found that target cells, erythrocytosis, and the ratios alone or in combination with the RDW were not specific in separating heterozygous thalassemia from iron deficiency. They conclude that a sequential evaluation (to include iron and hemoglobin studies) of cases of microcytosis is still needed.     

An algorithm to aid in the investigation of thalassemia trait in multicultural populations

CONTEXT: The differentiation between iron deficiency and a thalassemia syndrome is an important consideration in the investigation of microcytic anemia. OBJECTIVE: An established statistical method was used to demonstrate the importance of considering ethnic background in combination with mean cell volume (MCV) in the investigation of beta-thalassemia trait in a multicultural urban population. DESIGN: Posttest probabilities for beta-thalassemia trait were calculated using likelihood ratios for various microcytic MCV ranges in conjunction with published pretest probabilities for beta-thalassemia trait based on ethnic background. SETTING: Regional hemoglobinopathy laboratory, St Joseph's Hospital, Hamilton, Ontario, Canada. PATIENTS: Patient data were derived from a previously published study. The original study cohort consisted of 789 patients aged 18 years or older who had an MCV less than 80 fL and were referred for routine complete blood count during a 6-month period. MAIN OUTCOME MEASURES: Posttest probabilities. RESULTS: Simplified tables for the determination of posttest probabilities for beta-thalassemia trait in individual patients based on ethnic background and MCV are provided. An algorithm to assist in determining when thalassemia investigations are indicated is presented. CONCLUSIONS: A high index of suspicion based on ethnic background and low MCV can provide increased sensitivity and specificity for the detection of thalassemia trait in centers with multicultural populations similar to the study population.     

检测血液参数在常见小细胞性贫血患者中诊断鉴别的意义

目的明确不同检测血液参数在常见小细胞性贫血患者鉴别诊断中的意义。方法获取2017年10月至2018年9月在北京协和医院就诊的铁代谢相关疾病患者的血液标本,进行常规化验检查,同时检测网织红细胞血红蛋白含量(CHr)、铁蛋白(SF)、可溶性转铁蛋白受体(sTfR)、铁调素(hepcidin)等铁代谢相关指标,并比较其在不同疾病中表达的异同。结果缺铁性贫血(IDA)26例,慢性病性贫血(ACD)12例,地中海贫血(TA)12例,伴环形铁粒幼细胞增多的难治性贫血(RARS)12例。另有17名健康对照(NC)。平均红细胞体积(MCV):IDA和TA明显低于对照(P<0.01),且TA更低。平均红细胞血红蛋白浓度(MCHC):ACD、IDA、TA、RARS均显著低于NC(P<0.01),其中IDA最低。网织红细胞计数:除RARS外,其他3者均显著高于NC(P<0.01),TA相较于ACD、IDA升高更为明显。CHr:ACD、IDA、TA较NC显著下降(P<0.01)。SF在IDA患者中较NC显著下降(P<0.01)且低于其他3种贫血,而ACD、RARS较NC显著升高(P<0.01)。转铁蛋白饱和度(TS)中:ACD、IDA、TA相对NC降低(P<0.01),而RARS相对NC显著升高(P<0.01),且高于其他3种贫血。sTfR和sTfR指数(sTfR/log SF)在IDA患者中相较于NC显著升高(P<0.01),且相对ACD、TA、RARS更高。ROC曲线分析显示:SF、sTfR指数对鉴别诊断IDA和ACD、TA、RARS具有较高的诊断准确性。结论综合利用外周血检测的常规指标及铁代谢参数指标可以初步区分不同类型的小细胞贫血并辅助鉴别诊断。     

Elliptocytes and tailed poikilocytes correlate with severity of iron-deficiency anemia

This study examines the relationships between abnormal RBC morphology, RBC indices measured with an automated hematology analyzer, serum iron studies, and severity of anemia in patients with findings indicative of iron-deficiency anemia. Counts and morphologic classification of 1,000 RBCs from each of 22 patients were performed, and correlations were determined between parameters. The Student t test was used to determine the level of significance for correlations between parameters. Several significant relationships were found. As the percentage of elliptocytes increased, hemoglobin concentration, hematocrit, RBC concentration, and mean corpuscular hemoglobin level decreased (r = .48, .44, .40, and .49, respectively; P < .05). As the percentage of tailed poikilocytes increased, hemoglobin concentration, hematocrit, and RBC concentration decreased (r = .70, .77, and .71, respectively; P < .01) and RBC distribution width increased (r = .73; P < .01). Of significance, serum ferritin levels, long considered the best single indicator of iron deficiency, showed no correlation with the morphologic abnormalities assessed, severity of anemia, or any of the analyzer-generated indices. Our results indicate that microscopic evaluation of RBC morphology remains an important tool for the pathologist to evaluate the severity of anemia in patients with iron deficiency.     

Usefulness of reticulocyte hemoglobin equivalent for the safety of pre-operative autologous blood donation

Pre-operative autologous blood donation (PABD) provides safe blood for patients at the expense of the risk of iron deficiency anemia that may compromise the patients. The reticulocyte hemoglobin equivalent (RET-He) is an indirect measure of the functional iron available for the erythropoiesis over the previous 2-3 days. The aim of this study was to evaluate the clinical usefulness of RET-He quickly measured by the automated hematology analyzer Sysmex XE-2100 in patients undergoing PABD at our hospital. Receiver-operating characteristic curve analysis revealed that RET-He was reliable in the diagnosis of iron deficiency anemia. Two of 14 patients in the absence of post-PABD iron replacement developed marked anemia with low RET-He levels after PABD, suggesting that this anemia was due to iron deficiency. Of 26 patients receiving post-PABD iron replacement, 8 who had already showed low RET-He levels at PABD developed statistically significant reduction in hemoglobin levels after PABD despite adequate iron replacement, indicating that the 8 patients had iron deficiency prior to PABD. These findings suggest that automated measurement of RET-He may contribute to improve the safety of PABD.     

术前单用静脉铁剂对胃肠肿瘤相关性贫血的治疗作用

目的评估术前单用静脉铁剂对升高胃肠肿瘤合并贫血患者的治疗作用。方法收集2010年6月-2012年2月北京协和医院基本外科住院并接受手术治疗的胃肠肿瘤合并术前贫血的患者,对贫血合并缺铁的患者给予静脉铁剂治疗,在手术当日晨起或铁剂治疗后第14天晨起复查血常规、血清铁、铁蛋白水平、转铁蛋白以及肝肾功能的检查,记录围手术期患者接受输血剂量,与同期住院合并贫血患者的围手术期输血量进行比较。结果共有121例患者入组。术前静脉铁剂的应用能迅速的提高血色素水平,升高红细胞数量,改善红细胞的MCV、MCHC和MCH指标。静脉铁剂治疗后短期内血清铁以及血清铁蛋白水平显著升高(P<0.05)。治疗前血色素水平≥100 g/L的患者对静脉铁剂的反应较差。铁剂治疗组与同期未行铁剂治疗的胃肠肿瘤并贫血患者围手术期平均输血量差别比较明显(P<0.05)。结论在胃肠肿瘤合并贫血患者中,单用静脉铁剂能安全、快速提高患者的血色素水平以及机体缺铁状态,并降低贫血患者围手术期输血量。静脉铁剂的疗效可能受贫血程度影响。     

Hemoglobin A2 levels in health and various hematologic disorders.

Using a method involving elution of hemoglobin bands from cellulose acetate strips following electrophoresis of hemolysates, hemoglobin A2 (Ab A2) was quantitated in bloods from 300 healthy individuals and 904 patients. The percentage of Hb A2 was elevated in beta-thalassemia heterozygotes and some patients who had megaloblastic anemia. In the latter, the highest Hb A2 levels were observed in patients with the most severe anemia. Low Hb A2 percentages were found in iron-deficiency anemia, hereditary persistance of fetal hemoglobin, and Hb H disease. In iron-deficiency anemia, the lowest levels of Hb A2 were observed in association with the most severe anemia. Iron and folate deficiency each suppressed Hb A2 levels in beta-thalassemia heterozygotes; however, vitamin B12 deficiency did not alter the percentage of Hb A2 in thalassemia. Malignant tumors, renal and hepatic insufficiency, chronic infections and inflammation, hemolytic disease, lead poisoning, aplastic anemia, leukemia, myelofibrosis, and hypothyroidism did not change Hb A2 levels. The pathogenesis of altered Hb A2 levels and their clinical significance in various diseases are discussed.