Microcytic Red Blood Cells Research Articles

Characterization of a novel deletion causing (δβ)0‐thalassemia in a Thai family

A novel deletion of the human beta-globin gene cluster associated with the increased level of fetal hemoglobin (Hb F) in adult life has been demonstrated in a Thai family. A Thai girl who was mistakenly diagnosed as beta-thalassemia/HbE is found to be the compound heterozygote of this mutation and Hb E. The heterozygous father had mild hypochromic and microcytic red blood cells and a high level of Hb F (23.2%). Polymorphic restriction sites in the beta-globin gene cluster identified the homozygous alleles, which localized the deletion region between the psibeta-globin and the 3' beta-globin genes. DNA polymerase that can amplify a long DNA template was employed to examine DNA fragment encompassing this deletion. A 11.3 kilobases (kb) of DNA deletion, beginning approximately 3.1 kb 5' to the delta-globin gene and end in the intron 2 of the beta-globin gene was detected. DNA analysis revealed that this is a case of (deltabeta)(0)-thalassemia with a novel mutation, which can lead to a mild form of beta-thalassemia upon interaction with Hb E.

The Platelet Count/Mean Corpuscular Hemoglobin Ratio Distinguishes Combined Iron and Vitamin B 12 Deficiency from Uncomplicated Iron Deficiency

Combined deficiencies of iron and cobalamin are common. The aims of this study were to investigate the significance of the parameters of the complete blood count (CBC) in differentiating microcytic anemia due to pure iron deficiency anemia (IDA) from anemia due to combined deficiencies of vitamin B(12) and iron (IDA-B12). The study was carried out with 122 patients (100 female) who had microcytic red blood cell indices with IDA-B12 and 105 patients (95 female) with IDA. Group IDA-B12 patients had decreased hemoglobin levels, mean corpuscular volumes, mean corpuscular hemoglobin (MCH) levels, and MCH concentrations but had increased platelet counts (PLT). Using these parameters, we developed a PLT/MCH ratio parameter that has high values when IDA is accompanied by cobalamin deficiency. The cutoff value of >12.00, with a 74.6% sensitivity and a 41.9% specificity, appears to be the most convenient value for screening. We advise measuring the levels of cobalamin in patients with IDA associated with a high PLT/MCH ratio.

Genetic insights into the clinical diversity of beta thalassaemia.

Genetic insights into the clinical diversity of beta thalassaemia.

Inflammation and pruritus in haemodialysis patients.

Pruritus is a common symptom among patients on haemodialysis (HD). We studied 68 HD patients to assess the role of iron deficiency, anaemia, inflammation and other common serum and dialysis parameters in pruritus. The patients were questioned about the occurrence of pruritus at home, quantified according to frequency ('never', 'occasionally' and 'every day') and intensity ('absent', 'moderate' and 'severe'). The blood and serum variables considered were: haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, hypochromic red blood cells (RBC), hyperchromic RBC, microcytic RBC, macrocytic RBC, reticulocytes, iron, ferritin, transferrin, transferrin saturation, C-reactive protein (CRP), urea, creatinine, calcium, phosphorus, albumin, total protein and glucose. We also analysed Kt/V, age and time on HD treatment. Patients were divided into 3 groups according to the frequency or intensity of their pruritus, and we analysed and compared the variables between the 3 groups. Half (50%) of the patients reported never having pruritus, 32.4% occasionally and 17.6% every day. Pruritus was moderate in 41.2% of them and severe in 8.8%. None of the parameters considered revealed any statistically relevant differences between the three pruritus frequency groups, except for mean serum transferrin level (mg/dl) ('never'=268+/-64 vs 'occasionally'=244+/-40 vs 'every day'=217+/-56, P<0.05). As for the intensity of the symptom, mean serum transferrin (268+/-64 vs 247+/-39 vs 174+/-31, P<0.001) and median ferritin levels (mg/dl) (83 (11-420) vs 98 (11-1121) vs 293 (111-471), P<0.05) showed statistically significant differences between the 3 groups, as did albumin levels (g/dl) (4.3+/-0.4 vs 4.2+/-0.4 vs 3.7+/-0.4, P<0.05). Median CRP values (mg/dl) tended to be higher in patients with more frequent (0.4 (0.3-5.5) vs 0.7 (0.3-11.4) vs 0.9 (0.3-13.5)) and more severe pruritus (0.4 (0.3-5.5) vs 0.7 (0.3-4.0) vs 2.1 (0.3-13.5)), but those differences were not statistically significant. Iron deficiency and anaemia seem to play no part in HD-related pruritus, whereas lower serum transferrin and albumin levels and higher ferritin values are consistent with the possible role of inflammation in the development and severity of pruritus.

Iron-Deficiency Anemia Due to Silent Celiac Sprue

Celiac sprue, a gluten-induced enteropathy, was once considered primarily an immunologic disease of infants and children. Gluten is a protein found in grains, primarily wheat and barley. The ingestion of gliadin, a component of gluten, causes gastrointestinal symptoms including malabsorption and multiple nutritional deficiencies. Our understanding of this disorder has become more refined in recent years, as the case studies demonstrate. Case 1: A 14-year-old male student presented for a routine athletic physical examination. He reported no cardiovascular or gastrointestinal symptoms and had gained weight. His examination was normal; however, his blood hemoglobin was 11.6 g/dL, with microcytic red blood cells and a ferritin level of 5 ng/mL. Upper and lower endoscopic findings were macroscopically normal. Biopsy of the proximal duodenum showed villous atrophy and lymphocytic infiltrate in the lamina propria. Subsequent se-rologic studies revealed an anti-immunoglobulin A (IgA) tissue-transglutaminase antibody level of 6.88 units (normal is <1.0), and the anti-IgA endomysial antibody titer was positive (1:640). A gluten-free diet was instituted, and after 1 year the blood hemoglobin was 15.7 g/dL with restoration of ferritin and all serologic levels to normal. The student remains without symptoms and plays linebacker on his varsity football team. Case 2: In 1992, a 41-year-old woman, referred by her gynecologist, presented with a blood hemoglobin of 6.7 g/dL. She was on hormone replacement therapy with no menstrual bleeding. Her ferritin was unmeasurable. The patient denied any symptoms or weight loss, and except for pallor, her examination results were normal. Iron repletion with oral elixir increased her blood hemoglobin to 12 g/dL in 1 year, without elevation of the ferritin. In November 2000, a bone mineral density study revealed severe osteoporosis requiring therapy with alendronate. She remained asymptomatic. Serologic studies for celiac sprue were obtained. The anti-IgA tissue transglutaminase antibody level was 5.1 units. The anti-IgA endomysial antibody titer was positive (1:320). After 5 months on a gluten-free diet, her study results returned to normal and she remained without symptoms. In recent decades, the pathophysiology of celiac sprue has been clarified. Environmental, immunologic, and genetic factors are responsible for the histologic findings of flattening and atrophy of the small intestinal mucosal villi, crypt elongation, and lymphoid proliferation in the lamina propria. These changes may account for decreased levels of disaccharidase, alkaline phos-phatase, and hydrolases, predisposing patients to lactose intolerance and other functional defects in the intestinal mucosa. This condition requires the antigenic stimulus of gluten in the small intestine, causing formation of IgA antibodies directed against gliadin and tissue transglutaminase. When detected, these antibodies are 90% to 95% sensitive and specific for celiac sprue (1). Individuals sharing these findings are usually of European descent; the prevalence of the condition is 1 per 300 of the general white population. Evidence exists for possible dominant inheritance with incomplete expression of the genetic influence. There is a female predominance, and the incidence is higher in HLA-DQ2 phenotypes. Signs and symptoms may occur from infancy to the eighth decade of life. Fewer than half of affected patients complain of diarrhea. In an Italian study of 252 celiac sprue patients, only 43% displayed classic gastrointestinal symptoms. The symptomatic patient may have steatorrhea with malabsorption syndrome or selected deficiencies of iron, folate, or protein. Clinical manifestations include refractory anemia, osteoporosis, dermatitis herpetiformis, or neurologic signs. A feared complication in untreated disease is intestinal lymphoma (2, 3). Celiac sprue is definitively diagnosed by small intestinal biopsy, but the serologic test for IgA antibody against tissue transglutaminase is extremely accurate. This test has replaced the older test for the IgA antibody against endomysial antigen, which may be absent even in severe disease (4). Due to the requirement for strict dietary compliance, many experts advocate small bowel biopsy before initiation of the gluten-free diet. Interesting associations link celiac sprue with other immunologic conditions including insulin-dependent diabetes melli-tus, autoimmune thyroid disease, and IgA deficiency (5). Celiac sprue is treated with a strict lifelong avoidance of grains containing gluten. There are many sources of “hidden gluten,” including fillers in toothpaste, certain patent medications, deodorants, cosmetics, seasonings, and any grain-fermented alcohol. Even microscopic amounts of gluten may trigger intestinal reactions. Symptoms and histologic and serologic findings return to normal in a matter of months in patients who comply with the diet (6). The diagnosis of celiac sprue should be considered in any patient presenting with unexpected or unexplained deficiencies of iron, folate, or other elements, or with nonspecific gastrointestinal complaints undiagnosed by conventional studies. The high prevalence in the general population and the grave consequences of misdiagnosis make celiac sprue a significant health hazard.

Quantitative determinations of microcytic-hypochromic red blood cell population and glycerol permeability in iron-deficiency anemia and beta thalassemia minor.

The Hl/H2 Technicon automated cell analyzer measures, in addition to the usual red blood cell (RBC) parameters, subpopulations of microcytic (M) and hypochromic (H) red blood cells. The M/H ratio may be useful in the differential diagnosis of iron-deficiency anemia (IDA) and beta thalassemia minor (Thal). Thirty-three iron-deficient patients and 26 thalassemia patients were studied. The M/H ratio was found to be higher in thalassemia patients than in IDA patients. Using a cut-off point of 1.9 M/H ratio, the calculated discriminant efficiency was 88%. When glycerol lysis values were determined at 70 s as a cut-off point, the discriminant efficiency was slightly higher, at 91%. Thus, the combination of the M/H ratio and the glycerol lysis time (GLT) improves the discriminant efficiency and provides a good diagnostic tool to differentiate between the two microcytic-hypochromic anemias. The study suggests that the M/H ratio together with the GLT could serve as a useful screening tool, prior to the application of other more sophisticated methods.

Surface and metabolic properties of microcytic and macrocytic human anaemic red blood cells detected in polymer aqueous two-phase systems

Microcytic and macrocytic red blood cells from anaemic patients have been fractionated as a function of cell surface properties by the countercurrent distribution technique using charge-sensitive dextran/poly(ethylene glycol) aqueous two-phase systems. As deduced from the fractionation profiles, microcytic cells constitute a heterogeneous cell population with decreased surface charge properties while, macrocytic cells constitute a homogeneous cell population with behaviour similar to that of the control red blood cells. The specific activity of pyruvate kinase, an age-dependent enzyme, did not change along microcytic red blood cells fractionation profiles, suggesting that such cells have altered ageing properties. However, pyruvate kinase specific activity decreases from the left- to the right-hand side of the fractionation profile of macrocytic red blood cells, indicating that these cells follow the normal ageing process. Bisphosphoglycerate mutase specific activity did not change along the fractionation profile of any cell population under study, thus providing 2,3-bisphosphoglycerate during the life-span of the red blood cells from anaemic patients.

Red blood cell abnormalities in hereditary elliptocytosis and their relevance to variable clinical expression.

Marked variations are seen in the clinical manifestations of hereditary elliptocytosis (HE). To define the cellular alteration(s) that best reflect the variable expression of the disease, we evaluated the pathobiologic features of red blood cells in a series of 18 patients with HE, 15 persons from six families with HE as a result of defects in spectrin, and 3 persons from one family with HE caused by partial or total deficiency of protein 4.1. We found that decreased cellular deformability is a distinguishing feature of red blood cells in all patients studied. Comparison of volume and hemoglobin content histograms of red blood cells and reticulocytes revealed that cell fragmentation is a feature of mature red blood cells. The extent of red blood cell fragmentation as reflected by increased percentage of microcytic red blood cells was the best indicator of the severity of hemolytic anemia. Furthermore, we found that the observed variations in cellular properties of HE red blood cells in different persons is the consequence of varying amounts of mutant protein assembled into the membrane. These findings enabled us to define the mechanistic basis for cellular changes in this red blood cell membrane disorder better and also to obtain insight into the cellular basis for variable clinical expression.

Increased susceptibility of microcytic red blood cells to in vitro oxidative stress.

Oxidative damage to erythrocytes in thalassaemia has been related to generation of free radicals by an excess of denaturated alpha- or beta-globin chains, intracellular iron overload and low concentration of normal haemoglobin (HGB). Two good indicators of such oxidative damage are the high red blood cell (RBC) malonyldialdehyde (MDA) production detected following exogenous oxidant stress and the decrease of pyrimidine 5'-nucleotidase (P5N), the most sensitive enzyme to SH-group damage in vivo. Conflicting data, however, have so far accumulated in the literature concerning differences in oxidative damage between the different forms of thalassaemia and iron deficiency anaemia (IDA). In the present study, oxidative susceptibility, as defined by the production of MDA in vitro and antioxidant capacity, as measured by the activity of RBC glutathione peroxidase (GPx), superoxide dismutase (SOD) and by reduced glutathione (GSH), have been studied in microcytic RBCs from patients with beta-thalassaemia trait, Spanish (delta beta) zero-thalassaemia heterozygotes (delta beta-thalassaemia trait) and iron deficiency anaemia (IDA). The results are consistent with the existence of significant differences in the severity and pattern of oxidative stress susceptibility between beta-thalassaemia trait (increased MDA production and higher SOD and GPx activities) and the other two forms of microcytosis (delta beta thalassaemia trait and IDA). Furthermore, the finding of normal P5' N activity in delta beta thalassaemia trait, gives further support to the less intense peroxidative environment of RBCs in this form of thalassaemia when compared to beta-thalassaemia trait, characterized by acquired RBC P5' N deficiency due to oxidative damage.

Haematological and platelet effects of butylated hydroxytoluene (BHT, E321)

Inclusion of butylated hydroxytoluene (BHT) in the diet of rats, at a dose level of 3 g/kg/day for up to 14 or 21 days, caused modest, but persistent, increases in platelet count, microcytic red blood cell count and red blood cell glutathione (up to 144%, 280% and 197% of control values respectively). These changes were directly BHT-related but unrelated to its hepatotoxicity and independent of vitamin K status. Transient increases in red blood cell count, haematocrit and haemoglobin and transient decreases in reticulocyte, white blood cell and neutrophil counts were, however, related to the early but temporary reduction in food and water intake in the initial stages of feeding the BHT-containing diet. The apparent microcytosis was not accompanied by any other evidence of haemolytic anaemia and may, therefore, have arisen as an artifactual consequence of platelet abnormalities. The cause of the increased platelet phenomenon is not yet characterised but may be an adaptive response to a BHT-related platelet dysfunction and does not appear to be life threatening since an 8-fold increase in mean platelet count has been observed without any detectable adverse effect on thrombogenesis. It is suggested that BHT, given in high doses, could prove to be a useful tool in the identification and characterisation of thrombopoietin.

Use of the Erythrogram in the Diagnosis of Iron Deficiency in Elderly Patients

In elderly patients the diagnosis of iron deficiency from full blood count indices is often difficult. We assessed an automated technique (numerical data of the erythrogram; Technicon H*1) by which the proportions of microcytic (< 60 fl) and/or hypochromic (< 28 g.dl-1) red blood cells are determined. Of 472 elderly patients investigated, 100 (21%) were found to have iron deficiency (plasma ferritin < or = 45 ng.ml-1). Less than two-thirds of patients with iron-deficient erythropoiesis (anaemia or microcytosis) had increased proportions of hypochromic and/or microcytic red blood cells. Furthermore, the erythrogram was not sensitive in detecting latent or early iron deficiency. The erythrogram also lacked specificity for iron deficiency anaemia as many patients with mild normocytic anaemia associated with chronic inflammatory disease had increased proportions of hypochromic and/or microcytic red blood cells. Although patients with iron deficiency had increased proportions of hypochromic normocytic (p < 0.01) and normochromic microcytic red blood cells (p < 0.05) compared to those with chronic inflammatory disease and normal or raised iron stores (ferritin > or = 100 ng.ml-1, n = 32), there was a large overlap between these two groups, and the grossly elevated erythrogram results in patients with iron deficiency were almost always associated with a mean cell volume (MCV) < 80 fl, whereas none of the patients with chronic inflammatory disease and normal or raised iron stores had an MCV < 80 fl. Thus the erythrogram does not appear to be of value in the routine assessment of iron status in elderly patients.

Recurrent gastrointestinal bleeding associated with myelofibrosis and diffuse intestinal telangiectasias

A TO-year-old retired nurse was admitted in November 1986 with hematnchezia and early satiety followed by recurrent gastrointestinal bleeding. Fifteen years earlier, she had been admitted with abdominal pain, bloody diarrhea, and severe dehydration. At that time, the rectum was normal at sigmoidoscopy; a barium radiograph study of the colon showed ulceration and thumbprinting in the ascending and proximal transverse colon; results of barium studies of the upper gastrointestinal tract and small intestine as well as a visceral arteriogram were normal. A presumptive diagnosis of ischemic colitis was made, and the patient’s acute illness resolved without specific therapy. Ten years before admission, the patient developed symmetric polyarticular arthralgias and a normochromic, normocytic anemia. She began aspirin therapy for presumed seronegative rheumatoid arthritis. One year later she had a month-long episode of fevers and leukopenia (white blood cell count, 3100) with marked leftward shift. A bone marrow aspiration and biopsy were nondiagnostic. Despite extensive evaluation, a specific etiology was not discovered, and the patient’s signs and symptoms resolved spontaneously. Four years before admission, she developed a chronic nonproductive cough. Wheezing was intermittently noted, and an allergist diagnosed “pollen asthma.” Despite weekly inoculations of “mixed allergens” and oral aminophylline, her dry cough persisted. A chest radiograph was interpreted as normal with the exception of calcified granulomas in the upper lobes. Results of pulmonary function tests were otherwise normal. During the z months before admission, she noted progressive fatigue and a 20-lb weight loss associated with early satiety. On admission for hematochezia, her medications included 12 buffered aspirin tablets per day for arthritis, thyroid hormone supplement for hypothyroidism, and hydrochlorothiazide for hypertension. On physical examination she was tachycardic but normotensive. Physical examination was also remarkable for a spleen tip palpated 3 cm below the left costal margin and bright red blood on rectal examination. Laboratory studies showed a hematocrit of 0.23 (23%) with a mean corpuscular volume of 80 fL, a white blood cell count of 5900, and a platelet count of 256,000. The peripheral smear showed microcytic and hypochromic red blood cells with occasional tear drops, acanthocytes, eliptocytes, and nucleated red blood cells; occasional metamyelocytes and myelocytes were present. An elevated partial thromboplastin time (PTT) of 39.3 seconds (control, 29.4 seconds) was attributed to heterozygous factor XI (FXI) deficiency with an FXI level of 38%; prothrombin and bleeding times were normal. A leukocyte alkaline phosphatase score was normal, as were serum electrolyte, blood urea nitrogen, creatinine, aminotransferase, and lactate dehydrogenase levels. Alkaline phosphatase concentration was elevated at 205 U/L (normal, I 120 UiL), and y-glutamyl transferase level was normal. Except for diffusely sclerotic vertabrae and hummeri, a chest radiograph was unremarkable. Management included red blood cell transfusions, raniti-

Prenatal Diagnosis of Hemoglobinopathies

Hemoglobinopathies are frequently occurring disorders for which prenatal diagnosis is possible. Couples in which one parent has microcytic hypochromic red blood cells; is of Southeast Asian, Mediterranean, Middle Eastern, Indian, or African origin; or had one previous child with a known hemoglobinopathy or a previous hydropic stillbirth should be investigated. The hemoglobinopathies have been the paradigm of prenatal diagnosis, and the lessons learned from their study are now being applied to a range of other genetic disorders for which the responsible genes have been identified.

Some effects on light scattering intensity and red blood cell size distribution histograms due to sphering.

At present most haematology blood cell analysers routinely provide red blood cell (RBC) size distribution histograms. Sophisticated improvements of the instruments have re-awakened interest in the study of size histograms. The quantitative information derived from the histograms may be applied more fruitfully if insight is available, with respect to some essential principles of sizing technology and methods for treatment of RBCs before measurement. In this study the consequences of sphering RBCs are investigated in relation to the generation of size distribution histograms by means of methods based on light scattering intensity (LSI). Sphering of RBCs results in considerably narrower histograms than upsphered RBCs. The overall signal to noise ratio increases and there is a broader gap between large platelets and microcytic RBCs. Narrower size distribution ranges will enable closer modes to be separated. Compared to unsphered RBCs, microcytic sphered RBCs yield increased LSI whereas macrocytic sphered RBCs yield decreased LSI.

Evaluation of red blood cell size distribution histograms: the fraction of microcytes.

A method is described for the assessment of the fraction of microcytes from the red blood cell (RBC) size distribution histogram. For quantification of the fraction of microcytes an upper threshold corresponding with a RBC volume of 70 fL is established. The reference interval for the fraction of microcytes covers a range from 0.01 to 0.09. In order to examine the relationship between the fraction of microcytes and the mean cell volume (MCV) values computer simulation studies were performed. The computer simulations are based on a Gaussian distributed reference RBC histogram as generated on a Technicon H 6000/H 601 Hematology Analyser. From our studies it is shown that determination of the fraction of microcytes yields a higher sensitivity than MCV values for detecting small populations of microcytes. In particular, measurement of the fraction of microcytes is very sensitive to minor changes in the MCV values if a normocytic RBC population combined with a microcytic RBC fraction shows a wide dispersion in their cell volumes.

Free Erythrocyte Protoporphyrin (FEP) II. The FEP Test is Clinically Useful in Classifying Microcytic RBC Disorders in Adults

Microcytic red blood cells (RBC) are commonly encountered in clinical medicine and are caused by disorders of heme synthesis [usually iron deficiency anemia (IDA) or anemia of chronic disease (ACD)] or disorders of globin synthesis (usually thalassemia syndromes or HbE). Using the clinical history and standard laboratory tests (hematocrit, per cent saturation of transferrin (% sat), serum ferritin, Hb electrophoresis, HBA2, and HbF) we classified 198 adults with microcytic RBC as follows: 48 IDA, 11 probable IDA, 11 iron-deficient erythropoiesis without anemia, 13 ACD, 42 alpha-thalassemia trait, 35 probable alpha-thalassemia trait, 20 beta-thalassemia trait, and 15 unclassified. In addition, we demonstrated that the FEP test reliably (83-90% of the time, depending on FEP methodology) classifies microcytic RBC states into disorders of heme synthesis vs. disorders of globin synthesis. Because of reliability and ease of measurement, we recommend the hematofluorometer FEP as the first step in the clinical laboratory evaluation of microcytic RBC disorders in both adults and children.

The Laboratory Evaluation of Microcytic Red Blood Cells

Microcytic red blood cell states are common clinical problems in both adult and pediatric age groups. The recent widespread availability of electronic blood cell counters for performing routine blood counts has increased the detection of microcytic red blood cells. Physicians must workup both symptomatic and asymptomatic patients with microcytic red blood cells before they can initiate proper therapy and/or counseling. The purpose of this review is threefold: (1) to discuss the causes of microcytic red blood cells in terms of disorders of decreased heme production vs. disorders of decreased globin production, (2) to review the clinical laboratory tests useful in differentiating microcytic red blood cell states, and (3) to present a practical approach for the laboratory workup of microcytic red blood cells.

Identification of hemoglobin E by the isopropanol solubility test

Hemoglobin (Hb) E (β26 Glu→Lys) is the most common abnormal hemoglobin (Hb) variant in the world. Homozygotes for HbE are mildly thalassemic as a result of the alternate splice mutation and present with a benign clinical picture (microcytic and mildly anemic) with rare clinical symptoms. Given that the human red blood cell (RBC) contains both HbE and excess α-chains along with minor hemoglobins, the consequence of HbE alone on RBC pathophysiology has not been elucidated. This becomes critical for the highly morbid βE-thalassemia disease. We have generated transgenic mice exclusively expressing human HbE (HbEKO) that exhibit the known aberrant splicing of βE globin mRNA, but are essentially non-thalassemic as demonstrated by RBC α/β (human) globin chain synthesis. These mice exhibit hematological characteristics similar to presentations in human EE individuals: microcytic RBC with low MCV and MCH but normal MCHC; target RBC; mild anemia with low Hb, HCT and mildly elevated reticulocyte levels and decreased osmotic fragility, indicating altered RBC surface area to volume ratio. These alterations are correlated with a mild RBC oxidative stress indicated by enhanced membrane lipid peroxidation, elevated zinc protoporphyrin levels, and by small but significant changes in cardiac function. The C57 (background) mouse and full KO mouse models expressing HbE with the presence of HbS or HbA are used as controls. In select cases, the HbA full KO mouse model is compared but found to be limited due to its RBC thalassemic characteristics. Since the HbEKO mouse RBC lacks an abundance of excess α-chains that would approximate a mouse thalassemia (or a human thalassemia), the results indicate that the observed in vivo RBC mild oxidative stress arises, at least in part, from the molecular consequences of the HbE mutation.

Red cell indices in normal adults residing at altitude from sea level to 2670 meters.

Hemoglobin (Hb), packed cell volume (PCV), red blood cells (RBCs), mean cell volume (MCV), and mean cell hemoglobin concentration (MCHC) were measured by a single operator in a single laboratory by means of an electronic particle counter in 942 healthy adults (491 females and 451 males) residing at five altitudes: 0, 1000, 1860, 2220, and 2670 meters above sea level. The subjects were carefully screened clinically, and subjects with low transferrin saturation (less than 15%) were excluded. In both sexes there was a differential behavior as a function of altitude, of Hb and PCV on the one hand, and number of RBCs on the other. The findings suggest the presence of two sequential mechanisms of adaptation to progressively lower atmosphere oxygen pressure: One operating from sea level to 1860 meters, which leads to a progressively increasing number of relatively microcytic RBC; and a second one -- from 1860 to 2670 meters -- in which there is an increased but constant number of progressively more normocytic RBC, so that a simplistic model of equal magnitude increases in the three parameters and is seen at 2670 meters, but not at the intermediate altitudes. The middle group's comparativity, essential to these interpretations, apparently was achieved with regard to time elapsed between sampling and testing and with regard to the people integrating the groups.

Increased blood viscosity in patients with cyanotic congenital heart disease and iron deficiency

I~I YPERVISCO SITY RESULTING FROM POLYCYTHEMIA has been reported frequently in children with cyanotic congenital heart disease. '-~ These patients are at high risk to develop cerebrovascular complications, if polycythemia is accompanied by iron deficiency and microcytosis? -; Iron-deficient microcytic red blood Cells from rabbits and rats were found to be less deformable than normal RBCs? ' To our knowledge rheologic studies on iron-deficient microcytic human RBCs have been reported in only two patients and demonstrate decreased filterability of RBCs in one case ~~ and increased viscosity in the other? The present study was undertaken to evaluate the effect of microcytosis on the viscosity of RBCs suspended in plasma or in albumin solution at a hematocrit of 60%. At this hematocrit, which is often observed in children with cyanotic heart disease, small changes in theologic properties of RBCs markedly influence blood viscosity. H PATIENTS AND METHODS Fifty-nine infants and children (age 6 months to 12 years) with various types of cyanotic congenital heart disease were studied with informed consent of the patient and/or parents. Five milliliters of venous blood were collected in plastic tubes containing powdered EDTA for the viscosity studies and 1 ml in tubes without anticoagulant for the determination of serum iron and total ironbinding capacity. The anticoagulated blood was centrifuged at 2,000 g. Plasma and buffy coat were removed separately. The RBCs were resuspended in the removed autologous plasma and in 1% albumin in NaCl-phosphate buffer solution (osmolality 300 m0sm/1; pH 7.40) at hematocrits of 60 _+ 1%. Hematocrit was measured in duplicate by the microhematocrit method. The values were not corrected for trapped plasma. Studies in our laboratory have shown that plasma trapping between the centrifuged RBCs is about 2% when RBCs are normo- or macrocytic and