Red cell abnormalities in hereditary spherocytosis: relevance to diagnosis and understanding of the variable expression of clinical severity

Targeted next-generation sequencing identifies novel deleterious variants in ANK1 gene causing severe hereditary spherocytosis in Indian patients: expanding the molecular and clinical spectrum

Hereditary Spherocytosis (HS) is a common cause of hemolytic anemia varying from mild to severe hemolysis due to defects in red cell membrane protein genes, namely ANK1, SPTB, SPTA1, SLC4A1, and EPB42. These genes are considerably very large spaning 40-50 exons making gene-by-gene analysis costly and laborious by conventional methods. In this study, we explored 26 HS patients harboring 21 ANK1 variants identified by next-generation sequencing (NGS), characteristics and spectrum of the detected ANK1variants were analyzed in this study. Clinically, all the HS patients showed moderate to severe transfusion-dependent hemolytic anemia, some requiring splenectomy. We identified 13 novel and 8 reported variants, mainly 9 frameshifts, 2 missense, 6 nonsense, and 4 splice site ANK1 variants, using NGS technology. Frameshifts were remarkably the most common variant type seen in Indian HS patients with ANK1 gene defects. We have also explored expression levels of red cell membrane ankyrin protein by flow cytometry in 14 HS patients with ANK1 gene defects and a significant reduction in ankyrin protein expression has been found. This report mainly illustrates the molecular and phenotypic heterogeneity of ANK1 variants causing HS in Indian patients. Ankyrin-1 mutations are a significant cause of loss of function in dominant HS in the Indian population. Comprehensive genetic and phenotypic evaluation assists in implementing the knowledge of genetic patterns and spectrum of ANK1 gene variants, providing molecular support for HS diagnosis.

Investigation of Red Blood Cells by Atomic Force Microscopy

Currently, much research is devoted to the study of biological objects using atomic force microscopy (AFM). This method’s resolution is superior to the other non-scanning techniques. Our study aims to further emphasize some of the advantages of using AFM as a clinical screening tool. The study focused on red blood cells exposed to various physical and chemical factors, namely hemin, zinc ions, and long-term storage. AFM was used to investigate the morphological, nanostructural, cytoskeletal, and mechanical properties of red blood cells (RBCs). Based on experimental data, a set of important biomarkers determining the status of blood cells have been identified.

Dynamics of erythrocytes in oscillatory shear flows: effects of S/V ratio

By combining a multiscale structural model of erythrocyte with a fluid-cell interaction model based on the boundary-integral method, we numerically investigate the dynamic response of erythrocytes in oscillatory shear flows (OSFs). The goal is to develop a novel experimental method to test the structural robustness of erythrocytes in transient mechanical loads with small time scales, conditions closely imitating the mechanical environment in vivo. Following the discovery of multiple response modes (wheeling, mode 1 tank treading, and mode 2 tank treading) under these conditions (Zhu & Asaro, 2019), we concentrate on deformation and stress inside RBCs driven by OSF, especially shear deformation of the membrane and the skeleton-bilayer dissociation stress, parameters that are related to mechanically induced structural remodeling such as vesiculation. Effects related to changes in surface area-to-volume (S/V) ratio are considered. Our results show that with the variation of the S/V ratio there could be significant change in terms of the occurrence of response modes even if other parameters are kept unchanged. For example, by reducing the S/V ratio of the cell, an asymmetric mode featuring a mixture of the wheeling and mode 2 tank treading responses is discovered. This mode is found to be associated with large skeleton-bilayer dissociation stress so that its potential impact on OSF-driven vesiculation should not be overlooked. By systematically examining the dependencies of skeleton deformation and skeleton-bilayer dissociation stress upon S/V, this study is critical for the development of the OSF technique in applications such as diagnosis since cell conditions are often reflected in its geometric properties.

Hereditary Xerocytosis: Differential Behavior of PIEZO1 Mutations in the N-Terminal Extracellular Domain Between Red Blood Cells and HEK Cells

Hereditary Xerocytosis, a rare hemolytic anemia, is due to gain of function mutations in PIEZO1, a non-selective cation channel activated by mechanical stress. How these PIEZO1 mutations impair channel function and alter red blood cell (RBC) physiology, is not completely understood. Here, we report the characterization of mutations in the N-terminal part of the protein (V598M, F681S and the double mutation G782S/R808Q), a part of the channel that was subject of many investigations to decipher its role in channel gating. Our data show that the electrophysiological features of these PIEZO1 mutants expressed in HEK293T cells are different from previously characterized PIEZO1 mutations that are located in the pore or at the C-terminal extracellular domain of the protein. Although RBC with PIEZO1 mutations showed a dehydrated phenotype, the activity of V598M, F681S or R808Q in response to stretch was not significantly different from the WT channels. In contrast, the G782S mutant showed larger currents compared to the WT PIEZO1. Interestingly, basal activity of all the mutated channels was not significantly altered at the opposite of what was expected according to the decreased water and cation contents of resting RBC. In addition, the features of mutant PIEZO1 expressed in HEK293 cells do not always correlate with the observation in RBC where PIEZO1 mutations induced a cation leak associated with an increased conductance. Our work emphasizes the role of the membrane environment in PIEZO1 activity and the need to characterize RBC permeability to assess pathogenicity to PIEZO1 mutants associated with erythrocyte diseases.

Use of Complete Blood Cell Count Components to Screen for Hereditary Spherocytosis in Neonates

BACKGROUND AND OBJECTIVES

The neonatal hereditary spherocytosis (HS) index, defined as the mean corpuscular hemoglobin concentration divided by the mean corpuscular volume, has been proposed as a screening tool for HS in neonates. In a population of mostly white infants, an HS Index >0.36 was 97% sensitive and >99% specific. We evaluated the utility of the HS Index among a more racially and ethnically diverse population and determined if its discrimination varies with total serum bilirubin (TSB) levels.

METHODS

Infants born at ≥35 weeks' gestation at 15 Kaiser Permanente Northern California hospitals from 1995 to 2015 were eligible (N = 670 272). Erythrocyte indices from the first complete blood count drawn at ≤7 days and TSB levels drawn at ≤30 days were obtained. Diagnoses of HS were confirmed via chart review.

RESULTS

HS was confirmed in 79 infants, 1.2 per 10 000. HS was more common among infants of white and "other" race or ethnicity and among those with higher peak TSB levels. The area under the receiver operating characteristic curve for the HS Index was 0.84 (95% confidence interval 0.78-0.90). Likelihood ratios ranged from 10.1 for an HS Index ≥0.380 to 0.1 for an HS Index <0.310. Dichotomized at 0.36, the HS Index was 56% sensitive and 93% specific. Discrimination of the HS Index appeared best among infants with TSB levels <10 mg/dL.

CONCLUSIONS

The HS Index, when obtained from a CBC drawn within the first week after birth, had only modest ability to alter the probability of HS.

αI-spectrin represents evolutionary optimization of spectrin for red blood cell deformability

Spectrin tetramers of the membranes of enucleated mammalian erythrocytes play a critical role in red blood cell survival in circulation. One of the spectrins, αI, emerged in mammals with enucleated red cells after duplication of the ancestral α-spectrin gene common to all animals. The neofunctionalized αI-spectrin has moderate affinity for βI-spectrin, whereas αII-spectrin, expressed in nonerythroid cells, retains ancestral characteristics and has a 10-fold higher affinity for βI-spectrin. It has been hypothesized that this adaptation allows for rapid make and break of tetramers to accommodate membrane deformation. We have tested this hypothesis by generating mice with high-affinity spectrin tetramers formed by exchanging the site of tetramer formation in αI-spectrin (segments R0 and R1) for that of αII-spectrin. Erythrocytes with αIIβI presented normal hematologic parameters yet showed increased thermostability, and their membranes were significantly less deformable; under low shear forces, they displayed tumbling behavior rather than tank treading. The membrane skeleton is more stable with αIIβI and shows significantly less remodeling under deformation than red cell membranes of wild-type mice. These data demonstrate that spectrin tetramers undergo remodeling in intact erythrocytes and that this is required for the normal deformability of the erythrocyte membrane. We conclude that αI-spectrin represents evolutionary optimization of tetramer formation: neither higher-affinity tetramers (as shown here) nor lower affinity (as seen in hemolytic disease) can support the membrane properties required for effective tissue oxygenation in circulation.

Density, heterogeneity and deformability of red cells as markers of clinical severity in hereditary spherocytosis

Hereditary spherocytosis (HS) originates from defective anchoring of the cytoskeletal network to the transmembrane protein complexes of the red blood cell (RBC). Red cells in HS are characterized by membrane instability and reduced deformability and there is marked heterogeneity in disease severity among patients. To unravel this variability in disease severity, we analyzed blood samples from 21 HS patients with defects in ankyrin, band 3, α-spectrin or β-spectrin using red cell indices, eosin-5-maleimide binding, microscopy, the osmotic fragility test, Percoll density gradients, vesiculation and ektacytometry to assess cell membrane stability, cellular density and deformability. Reticulocyte counts, CD71 abundance, band 4.1 a:b ratio, and glycated hemoglobin were used as markers of RBC turnover. We observed that patients with moderate/severe spherocytosis have short-living erythrocytes of low density and abnormally high intercellular heterogeneity. These cells show a prominent decrease in membrane stability and deformability and, as a consequence, are quickly removed from the circulation by the spleen. In contrast, in mild spherocytosis less pronounced reduction in deformability results in prolonged RBC lifespan and, hence, cells are subject to progressive loss of membrane. RBC from patients with mild spherocytosis thus become denser before they are taken up by the spleen. Based on our findings, we conclude that RBC membrane loss, cellular heterogeneity and density are strong markers of clinical severity in spherocytosis.

Applications of imaging flow cytometry in the diagnostic assessment of red cell membrane disorders

BACKGROUND

Red cell membranopathies refers to phenotypically and morphologically heterogeneous disorders. High throughput imaging flow cytometry (IFC) combines the speed, sensitivity, and phenotyping abilities of flow cytometry with the detailed imagery and functional insights of microscopy to produce high content image analysis with quantitative analysis. We have evaluated the applications of IFC to examine both the morphology as well as fluorescence signal intensity in red cell membranopathies.

METHODS

Fluorescence intensity of eosin-5-maleimide (EMA) labeled red cells was measured for diagnosis of RBC membrane protein defect on Amnis ImageStreamX followed by Image analysis on IDEAS software to study features such as circularity and shape ratio.

RESULTS

The hereditary spherocytosis (HS) group showed significantly decreased MFI (52,800 ± 9,100) than normal controls (81,100 ± 4,700) (p < .05) whereas non-HS showed 78,300 ± 9,900. The shape ratio of hereditary elliptocytosis (HE) was significantly higher (43.8%) than normal controls (14.6%). The circularity score is higher in HS (64.15%) than the normal controls (44.3%) whereas the circularity score was very less in HE (10%) due to the presence of elliptocytes.

CONCLUSIONS

The advantages of the IFC over standard flow cytometry is its ability to provide high-content image analysis and measurement of parameters such as circularity and shape ratio allow discriminating red cell membranopathies (HS and HE) due to variations in shape and size. It could be a single, effective, and rapid IFC test for detection and differentiation of red cell membrane disorders in hematology laboratories where an IFC is available.

The Complexity of Genotype-Phenotype Correlations in Hereditary Spherocytosis: A Cohort of 95 Patients: Genotype-Phenotype Correlation in Hereditary Spherocytosis

Supplemental Digital Content is available in the text

Hereditary spherocytosis (HS) is a phenotypically and genetically heterogeneous disease. With the increased use of Next Generation Sequencing (NGS) techniques in the diagnosis of red blood cell disorders, the list of unique pathogenic mutations underlying HS is growing rapidly. In this study, we aimed to explore genotype-phenotype correlation in 95 HS patients genotyped by targeted NGS as part of routine diagnostics (UMC Utrecht, Utrecht, The Netherlands). In 85/95 (89%) of patients a pathogenic mutation was identified, including 56 novel mutations. SPTA1 mutations were most frequently encountered (36%, 31/85 patients), primarily in patients with autosomal recessive forms of HS. Three SPTA1 (α-spectrin) mutations showed autosomal dominant inheritance. ANK1 (ankyrin1) mutations accounted for 27% (23/85 patients) and SPTB (β-spectrin) mutations for 20% (17/85 patients). Moderate or severe HS was more frequent in patients with SPTB or ANK1 mutations, reflected by lower hemoglobin concentrations and higher reticulocyte counts. Interestingly, mutations affecting spectrin association domains of ANK1, SPTA1 and SPTB resulted in more severe phenotypes. Additionally, we observed a clear association between phenotype and aspects of red cell deformability as determined by the Laser assisted Optical Rotational Cell Analyzer (LoRRca MaxSis). Both maximal deformability and area under the curve were negatively associated with disease severity (respectively r = −0.46, p < 0.01, and r = −0.39, p = 0.01). Genotype-phenotype prediction in HS facilitates insight in consequences of pathogenic mutations for the assembly and dynamic interactions of the red cell cytoskeleton. In addition, we show that measurements of red blood cell deformability are clearly correlated with HS severity.

Molecular diagnosis of hereditary spherocytosis by multi-gene target sequencing in Korea: matching with osmotic fragility test and presence of spherocyte

Background

Current diagnostic tests for hereditary spherocytosis (HS) focus on the detection of hemolysis or indirectly assessing defects of membrane protein, whereas direct methods to detect protein defects are complicated and difficult to implement. In the present study, we investigated the patterns of genetic variation associated with HS among patients clinically diagnosed with HS.

Methods

Multi-gene targeted sequencing of 43 genes (17 RBC membrane protein-encoding genes, 20 RBC enzyme-encoding genes, and six additional genes for the differential diagnosis) was performed using the Illumina HiSeq platform.

Results

Among 59 patients with HS, 50 (84.7%) had one or more significant variants in a RBC membrane protein-encoding genes. A total of 54 significant variants including 46 novel mutations were detected in six RBC membrane protein-encoding genes, with the highest number of variants found in SPTB (n = 28), and followed by ANK1 (n = 19), SLC4A1 (n = 3), SPTA1 (n = 2), EPB41 (n = 1), and EPB42 (n = 1). Concurrent mutations of genes encoding RBC enzymes (ALDOB, GAPDH, and GSR) were detected in three patients. UGT1A1 mutations were present in 24 patients (40.7%). Positive rate of osmotic fragility test was 86.8% among patients harboring HS-related gene mutations.

Conclusions

This constitutes the first large-scaled genetic study of Korean patients with HS. We demonstrated that multi-gene target sequencing is sensitive and feasible that can be used as a powerful tool for diagnosing HS. Considering the discrepancies of clinical and molecular diagnoses of HS, our findings suggest that molecular genetic analysis is required for accurate diagnosis of HS.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1070-0) contains supplementary material, which is available to authorized users.

The role of the erythrocyte in the outcome of pregnancy with preeclampsia

The objective of this study was to analyze the relationships of osmotic and mechanical stability of erythrocytes with anthropometric, biochemical, hematologic and hemodynamic variables in pregnant women with preeclampsia (PE). The studied population consisted of 20 normotensive patients and 16 patients with PE. Patients with PE presented worse gestational outcome, greater hematologic impairment, erythrocytes osmotically more stable in vitro, but in conditions of isotonicity with the in vivo medium, in addition to hyperflow in orbital territory, when compared to normotensive patients. The correlation analysis between anthropometric, hematologic and hemodynamic variables in patients with PE indicated that erythrocytes with lower volumes and lower levels of hemoglobin favor the occurrence of a better gestational outcome, because they are more stable and because they are associated with a decrease in the hemodynamic changes present in the disease. This should mean that the tendency to microcytosis, probably due to a mechanism of compensatory mechanical selection, is a desirable characteristic in the disease.

Clinical and biological features in PIEZO1-hereditary xerocytosis and Gardos channelopathy: a retrospective series of 126 patients

We describe the clinical, hematologic and genetic characteristics of a retrospective series of 126 subjects from 64 families with hereditary xerocytosis. Twelve patients from six families carried a KCNN4 mutation, five had the recurrent p.Arg352His mutation and one had a new deletion at the exon 7-intron 7 junction. Forty-nine families carried a PIEZO1 mutation, which was a known recurrent mutation in only one-third of the cases and private sequence variation in others; 12 new probably pathogenic missense mutations were identified. The two dominant features leading to diagnosis were hemolysis that persisted after splenectomy and hyperferritinemia, with an inconstant correlation with liver iron content assessed by magnetic resonance imaging. PIEZO1-hereditary xerocytosis was characterized by compensated hemolysis in most cases, perinatal edema of heterogeneous severity in more than 20% of families and a major risk of post-splenectomy thrombotic events, including a high frequency of portal thrombosis. In KCNN4-related disease, the main symptoms were more severe anemia, hemolysis and iron overload, with no clear sign of red cell dehydration; therefore, this disorder would be better described as a ‘Gardos channelopathy’. These data on the largest series to date indicate that PIEZO1-hereditary xerocytosis and Gardos channelopathy are not the same disease although they share hemolysis, a high rate of iron overload and inefficient splenectomy. They demonstrate the high variability in clinical expression as well as genetic bases of PIEZO1-hereditary xerocytosis. These results will help to improve the diagnosis of hereditary xerocytosis and to provide recommendations on the clinical management in terms of splenectomy, iron overload and pregnancy follow-up.

Flow Cytometric Analysis of Erythrocytes Osmotic Fragility in Hereditary Spherocytosis: A Case-Controlled Study Evaluating the Best Anticoagulant, Sample Pre-Treatment and NaCl Concentration for Reliable Screening of this Red Blood Cell Membrane Disorder

BACKGROUND

The cytometric flow osmotic fragility test (FC-OFT) was recently introduced. However, the test is still under development and some variables have not yet been fully tested.

METHODS

The osmotic fragility of hereditary spherocytosis (HS) cases and healthy controls were evaluated by FC-OFT using a series of tubes containing decreasing concentrations of NaCl. The analyses were executed in fresh and incubated (37°C for 24 h) blood samples anticoagulated with EDTA and heparin. The percentages of residual red blood cells were used to plot the osmotic fragility curves. The OF curves of each tested condition were compared using the median corpuscular fragility (MCF). ROC curve analyses identified the most accurate NaCl concentrations for differentiation between HS cases and healthy controls.

RESULTS

FC-OFT curves assumed a sigmoidal dose-response shape and the MCF of cases and controls were different in all instances. MCF comparisons revealed that incubation and anticoagulant have major and minor effects on the FC-OFT, respectively. One hundred percent of sensitivity and specificity was obtained from 5.5 to 6.0 g/L of NaCl in EDTA-treated fresh blood, from 6.0 to 8.0 g/L of NaCl in EDTA-treated incubated blood, and in none of the tested NaCl concentration in heparinized blood.

CONCLUSIONS

EDTA is the anticoagulant of choice for the assay. Incubation at 37°C for 24 h increased its diagnostic capability. The most reliable NaCl concentration for the discrimination of HS case from controls was 6.0 g/L of NaCL in fresh EDTA-treated blood, and was 7.5 g/L of NaCl in incubated EDTA-treated blood. © 2018 International Clinical Cytometry Society.

Stabilization of F-actin by tropomyosin isoforms regulates the morphology and mechanical behavior of red blood cells

The absence of Tpm3.1 in red blood cells (RBCs) induces a compensatory increase in Tpm1.9 and abnormally stable F-actin in the membrane skeleton, with reduced association of Band 3 and glycophorin A, leading to a compensated hemolytic anemia with abnormal RBC shapes and mechanical properties.

The short F-actins in the red blood cell (RBC) membrane skeleton are coated along their lengths by an equimolar combination of two tropomyosin isoforms, Tpm1.9 and Tpm3.1. We hypothesized that tropomyosin’s ability to stabilize F-actin regulates RBC morphology and mechanical properties. To test this, we examined mice with a targeted deletion in alternatively spliced exon 9d of Tpm3 (Tpm3/9d^–/–), which leads to absence of Tpm3.1 in RBCs along with a compensatory increase in Tpm1.9 of sufficient magnitude to maintain normal total tropomyosin content. The isoform switch from Tpm1.9/Tpm3.1 to exclusively Tpm1.9 does not affect membrane skeleton composition but causes RBC F-actins to become hyperstable, based on decreased vulnerability to latrunculin-A–induced depolymerization. Unexpectedly, this isoform switch also leads to decreased association of Band 3 and glycophorin A with the membrane skeleton, suggesting that tropomyosin isoforms regulate the strength of F-actin-to-membrane linkages. Tpm3/9d^–/– mice display a mild compensated anemia, in which RBCs have spherocytic morphology with increased osmotic fragility, reduced membrane deformability, and increased membrane stability. We conclude that RBC tropomyosin isoforms directly influence RBC physiology by regulating 1) the stability of the short F-actins in the membrane skeleton and 2) the strength of linkages between the membrane skeleton and transmembrane glycoproteins.

Anemia for the Primary Care Physician

Anemia denotes a reduced red blood cell (RBC) mass from any cause. The causes of anemia are numerous and due to decreased (or abnormal) erythropoesis, shortened RBC life span, or blood loss. The most common etiology of anemia is iron deficiency. A judicious work up of anemia includes evaluating the reticulocyte count and peripheral smear. The severity of illness of a patient with anemia is determined by the degree of anemia and the seriousness of the underlying disorder. Management of patients with hereditary and hemolytic anemias should involve a hematologist.

Next-generation osmotic gradient ektacytometry for the diagnosis of hereditary spherocytosis: interlaboratory method validation and experience

Background:

Osmotic gradient ektacytometry is part of the laboratory diagnosis process of hereditary spherocytosis (HS) and other red blood cell (RBC) membrane disorders. We here present the experience of two independent institutions with a next-generation ektacytometer, the LoRRca MaxSis analyzer, in HS diagnostic settings.

Methods:

Inter- and intra-assay variability and sample stability were analyzed. Samples from patients with HS (n=40), probable HS (n=21), auto-immune hemolytic anemia (n=7), and other pathologies (n=37) were studied. Daily controls were run in parallel with patient samples. Results were expressed as percent of change compared to mean of controls.

Results:

Analytical performances showed an inter-assay variability between 0.2% and 3%. Samples were stable for 48–72 h depending of temperature storage and anticoagulant used. The following diagnostic cut-offs were established for HS: an increase of more than 21.5% for the osmolality point at the minimal elongation index (O min), a decrease of more than 8.5% for the maximal elongation index (EI max), and a decreased area under the curve (AUC) of more than 18.5% compared to the mean of controls.

Conclusions:

As the previous instrument, the next-generation ektacytometer is an efficient tool for laboratory diagnosis of HS. Sample stability and standardized reporting of results allow inter-laboratory exchange and comparison. The most useful parameters for HS diagnosis were AUC, EI max, and O min; unfortunately, this method does not differentiate between HS and auto-immune hemolytic anemia (AIHA), but it distinguishes HS from other hereditary membrane pathologies. It can thus be considered as an intermediate step between screening and diagnostic tests.

Red blood cell thickness is evolutionarily constrained by slow, hemoglobin-restricted diffusion in cytoplasm

During capillary transit, red blood cells (RBCs) must exchange large quantities of CO₂ and O₂ in typically less than one second, but the degree to which this is rate-limited by diffusion through cytoplasm is not known. Gas diffusivity is intuitively assumed to be fast and this would imply that the intracellular path-length, defined by RBC shape, is not a factor that could meaningfully compromise physiology. Here, we evaluated CO₂ diffusivity (D_CO2) in RBCs and related our results to cell shape. D_CO2 inside RBCs was determined by fluorescence imaging of [H⁺] dynamics in cells under superfusion. This method is based on the principle that H⁺ diffusion is facilitated by CO₂/HCO₃^- buffer and thus provides a read-out of D_CO2. By imaging the spread of H⁺ ions from a photochemically-activated source (6-nitroveratraldehyde), D_CO2 in human RBCs was calculated to be only 5% of the rate in water. Measurements on RBCs containing different hemoglobin concentrations demonstrated a halving of D_CO2 with every 75 g/L increase in mean corpuscular hemoglobin concentration (MCHC). Thus, to compensate for highly-restricted cytoplasmic diffusion, RBC thickness must be reduced as appropriate for its MCHC. This can explain the inverse relationship between MCHC and RBC thickness determined from >250 animal species.

[Flow cytometric test using eosin-5'-maleimide (EMA) labelling of red blood for diagnosis of hereditary spherocytosis]

目的

探讨伊红-5′-马来酰亚胺（EMA）为标记流式细胞术检测遗传性球形红细胞的灵敏性和特异性，并对试剂和样本稳定性进行验证。

方法

对80例遗传性球形红细胞增多症（HS）和44例非HS患者外周血样本全部采用EMA标记流式细胞术检测、红细胞渗透脆性试验和酸化甘油溶解试验三种方法进行检测，比较三种方法的灵敏性和特异性，探讨EMA标记流式细胞术检测的可行性。并观察EMA及样本在不同储存条件下的稳定性。

结果

通过检测124例样本得出，EMA标记流式细胞术检测的灵敏性和特异性分别为0.925和0.954，红细胞渗透脆性试验分别为0.950和0.455，酸化甘油溶解试验为1.000和0.318。红细胞渗透脆性试验和酸化甘油溶解试验的灵敏性稍高于EMA流式检测方法，但特异性差，不能明确区分球形红细胞增多是否为HS。EMA对温度很敏感，−80 °C储存180 d较4 °C存储1 d稳定。HS样本的稳定性较好，4 °C放置6 d、室温条件放置3 d不会影响结果的判定。

结论

EMA标记流式细胞术检测HS具有良好的灵敏性和特异性，−80 °C储存EMA较为稳定，须在样本4 °C放置6 d内、室温条件放置3 d内完成检测。

Evaluation of a Flow-Cytometric Osmotic Fragility Test for Hereditary Spherocytosis in Chinese Patients

BACKGROUND

Osmotic fragility testing based on flow cytometry was recently introduced for the screening of hereditary spherocytosis (HS). This study was undertaken to evaluate the clinical diagnostic value of a flow-cytometric osmotic fragility test for HS.

METHODS

Peripheral blood was collected from 237 subjects at the First Affiliated Hospital of Guangxi Medical University, including 56 HS patients, 86 thalassemia patients and 95 healthy controls. The samples were examined by flow-cytometric osmotic fragility test and the percentage of residual red blood cells was used to determine HS. Peripheral blood smears were performed to examine the red blood cell morphology.

RESULTS

With clinical diagnosis of HS as the gold standard and the percentage of residual red blood cells <23.6% as the diagnostic threshold in the flow-cytometric osmotic fragility test, the sensitivity of the flow-cytometric osmotic fragility test for HS was 85.71% and the specificity was 97.24%.

CONCLUSION

The flow-cytometric osmotic fragility test combined with a red blood cell morphology test by peripheral blood smear could be a simple, practical and accurate laboratory screening method for HS.

Diagnostic tool for red blood cell membrane disorders: Assessment of a new generation ektacytometer

Inherited red blood cell (RBC) membrane disorders, such as hereditary spherocytosis, elliptocytosis and hereditary ovalocytosis, result from mutations in genes encoding various RBC membrane and skeletal proteins. The RBC membrane, a composite structure composed of a lipid bilayer linked to a spectrin/actin-based membrane skeleton, confers upon the RBC unique features of deformability and mechanical stability. The disease severity is primarily dependent on the extent of membrane surface area loss. RBC membrane disorders can be readily diagnosed by various laboratory approaches that include RBC cytology, flow cytometry, ektacytometry, electrophoresis of RBC membrane proteins and genetics. The reference technique for diagnosis of RBC membrane disorders is the osmotic gradient ektacytometry. However, in spite of its recognition as the reference technique, this technique is rarely used as a routine diagnosis tool for RBC membrane disorders due to its limited availability. This may soon change as a new generation of ektacytometer has been recently engineered. In this review, we describe the workflow of the samples shipped to our Hematology laboratory for RBC membrane disorder analysis and the data obtained for a large cohort of French patients presenting with RBC membrane disorders using a newly available version of the ektacytomer.

Detection of red blood cell antibodies in mitogen-stimulated cultures from patients with hereditary spherocytosis

BACKGROUND

Hereditary spherocytosis (HS) is a congenital hemolytic anemia caused by defects in red blood cell (RBC) membrane proteins leading to premature RBC clearance in the spleen. The presence of RBC autoantibodies has never been extensively investigated in HS.

STUDY DESIGN AND METHODS

RBC antibody-bound immunoglobulin (Ig)G was investigated in 91 consecutive HS patients by mitogen-stimulated direct antiglobulin test (MS-DAT), a sensitive method able to magnify latent RBC antibody autoimmunity and related with hemolytic variables, previous splenectomy, and type of membrane defect.

RESULTS

A total of 61% of HS cases had RBC antibodies by MS-DAT (29 Band 3, 17 spectrin deficiency, and nine no defined defect). The amount of RBC-bound IgG was greater in HS compared with controls (236 ± 192 ng/mL vs. 52 ± 29 ng/mL, p < 0.0001), although lower than that observed in autoimmune hemolytic anemia (AIHA; 634 ± 371 ng/mL vs. 236 ± 192 ng/mL, p < 0.0001). Western blot experiments showed that purified IgG fraction from MS-DAT-positive patients bind to α- and β-spectrin, Band 3, and Band 4.9. Positive cases displayed increased reticulocytosis and slightly reduced hemoglobin (Hb) values compared to negative ones. Patients displaying RBC-bound IgG of more than 250 ng/mL (the positive threshold of AIHA) showed increased number of spherocytes and mainly had spectrin deficiency. RBC-bound IgG and free Hb increased over time after storage at 4°C, a surrogate of ex vivo aging, more evidently in HS than controls, and particularly in Band 3 deficiency.

CONCLUSION

RBC autoantibodies were detected by MS-DAT in more than a half of HS patients. Positive cases showed a more evident hemolytic pattern suggesting a pathogenic role of these autoantibodies in RBC opsonization and splenic removal.

A biomimetic microfluidic chip to study the circulation and mechanical retention of red blood cells in the spleen

Red blood cells (RBCs) are deformable and flow through vessels narrower than their own size. Their deformability is most stringently challenged when they cross micrometer-wide slits in the spleen. In several inherited or acquired RBC disorders, blockade of small vessels by stiff RBCs can trigger organ damage, but a functional spleen is expected to clear these abnormal RBCs from the circulation before they induce such complications. We analyzed flow behavior of RBCs in a microfluidic chip that replicates the mechanical constraints imposed on RBCs as they cross the human spleen. Polymer microchannels obtained by soft lithography with a hydraulic diameter of 25 μm drove flow into mechanical filtering units where RBCs flew either slowly through 5- to 2-μm-wide slits or rapidly along 10-μm-wide channels, these parallel paths mimicking the splenic microcirculation. Stiff heated RBCs accumulated in narrow slits seven times more frequently than normal RBCs infused simultaneously. Stage-dependent retention of Plasmodium falciparum-infected RBCs was also observed in these slits. We also analyzed RBCs from patients with hereditary spherocytosis and observed retention for those having the most altered mechanical properties as determined by ektacytometry. Thus, in keeping with previous observations in vivo and ex vivo, the chip successfully discriminated poorly deformable RBCs based on their distinct mechanical properties and on the intensity of the cell alteration. Applications to the exploration of the pathogenesis of malaria, hereditary spherocytosis, sickle cell disease and other RBC disorders are envisioned.

ICSH guidelines for the laboratory diagnosis of nonimmune hereditary red cell membrane disorders

INTRODUCTION

Hereditary spherocytosis (HS), hereditary elliptocytosis (HE), and hereditary stomatocytosis (HSt) are inherited red cell disorders caused by defects in various membrane proteins. The heterogeneous clinical presentation, biochemical and genetic abnormalities in HS and HE have been well documented. The need to raise the awareness of HSt, albeit its much lower prevalence than HS, is due to the undesirable outcome of splenectomy in these patients.

METHODS

The scope of this guideline is to identify the characteristic clinical features, the red cell parameters (including red cell morphology) for these red cell disorders associated, respectively, with defective cytoskeleton (HS and HE) and abnormal cation permeability in the lipid bilayer (HSt) of the red cell. The current screening tests for HS are described, and their limitations are highlighted.

RESULTS

An appropriate diagnosis can often be made when the screening test result(s) is reviewed together with the patient's clinical/family history, blood count results, reticulocyte count, red cell morphology, and chemistry results. SDS-polyacrylamide gel electrophoresis of erythrocyte membrane proteins, monovalent cation flux measurement, and molecular analysis of membrane protein genes are specialist tests for further investigation.

CONCLUSION

Specialist tests provide additional evidence in supporting the diagnosis and that will facilitate the management of the patient. In the case of a patient's clinical phenotype being more severe than the affected members within the immediate family, molecular testing of all family members is useful for confirming the diagnosis and allows an insight into the molecular basis of the abnormality such as a recessive mode of inheritance or a de novo mutation.

Profiling individual human red blood cells using common-path diffraction optical tomography

Due to its strong correlation with the pathophysiology of many diseases, information about human red blood cells (RBCs) has a crucial function in hematology. Therefore, measuring and understanding the morphological, chemical, and mechanical properties of individual RBCs is a key to understanding the pathophysiology of a number of diseases in hematology, as well as to opening up new possibilities for diagnosing diseases in their early stages. In this study, we present the simultaneous and quantitative measurement of the morphological, chemical, and mechanical parameters of individual RBCs employing optical holographic microtomography. In addition, it is demonstrated that the correlation analyses of these RBC parameters provide unique information for distinguishing and understanding diseases.

Biomechanical properties of red blood cells in health and disease towards microfluidics

Red blood cells (RBCs) possess a unique capacity for undergoing cellular deformation to navigate across various human microcirculation vessels, enabling them to pass through capillaries that are smaller than their diameter and to carry out their role as gas carriers between blood and tissues. Since there is growing evidence that red blood cell deformability is impaired in some pathological conditions, measurement of RBC deformability has been the focus of numerous studies over the past decades. Nevertheless, reports on healthy and pathological RBCs are currently limited and, in many cases, are not expressed in terms of well-defined cell membrane parameters such as elasticity and viscosity. Hence, it is often difficult to integrate these results into the basic understanding of RBC behaviour, as well as into clinical applications. The aim of this review is to summarize currently available reports on RBC deformability and to highlight its association with various human diseases such as hereditary disorders (e.g., spherocytosis, elliptocytosis, ovalocytosis, and stomatocytosis), metabolic disorders (e.g., diabetes, hypercholesterolemia, obesity), adenosine triphosphate-induced membrane changes, oxidative stress, and paroxysmal nocturnal hemoglobinuria. Microfluidic techniques have been identified as the key to develop state-of-the-art dynamic experimental models for elucidating the significance of RBC membrane alterations in pathological conditions and the role that such alterations play in the microvasculature flow dynamics.

Evaluation of red cell membrane cytoskeletal disorders using a flow cytometric method in South iran

OBJECTIVE

The diagnosis of hereditary red blood cell (RBC) membrane disorders, and in particular hereditary spherocytosis (HS) and Southeast Asian ovalocytosis (SAO), is based on clinical history, RBC morphology, and other conventional tests such as osmotic fragility. However, there are some milder cases of these disorders that are difficult to diagnose. The application of eosin-5'-maleimide (EMA) was evaluated for screening of RBC membrane defects along with some other anemias. We used EMA dye, which binds mostly to band 3 protein and to a lesser extent some other membrane proteins, for screening of some membrane defects such as HS.

MATERIALS AND METHODS

Fresh RBCs from hematologically normal controls and patients with HS, SAO, hereditary elliptocytosis, hereditary spherocytosis with pincered cells, severe iron deficiency, thalassemia minor, and autoimmune hemolytic anemia were stained with EMA dye and analyzed for mean fluorescent intensity (MFI) using a flow cytometer.

RESULTS

RBCs from patients with HS and iron deficiency showed a significant reduction in MFI compared to those from normal controls (p<0.0001 and p<0.001, respectively), while macrocytic RBCs showed a significant increase in MFI (p<0.01). A significant correlation was shown between mean corpuscular volume and MFI, with the exceptions of HS and thalassemia minor.

CONCLUSION

Our results showed that the flow cytometric method could be a reliable diagnostic method for screening and confirmation, with higher sensitivity and specificity (95% and 93%, respectively) than conventional routine tests for HS patients prior to further specific membrane protein molecular tests.

Abnormalities of the erythrocyte membrane

Primary abnormalities of the erythrocyte membrane are characterized by clinical, laboratory, and genetic heterogeneity. Among this group, hereditary spherocytosis patients are more likely to experience symptomatic anemia. Treatment of hereditary spherocytosis with splenectomy is curative in most patients. Growing recognition of the long-term risks of splenectomy has led to re-evaluation of the role of splenectomy. Management guidelines acknowledge these considerations and recommend discussion between health care providers, patient, and family. The hereditary elliptocytosis syndromes are the most common primary disorders of erythrocyte membrane proteins. However, most elliptocytosis patients are asymptomatic and do not require therapy.

Red cell indices in classification and treatment of anemias: from M.M. Wintrobes's original 1934 classification to the third millennium

PURPOSE OF REVIEW

Measurements of red cell volume, hemoglobin (Hb) concentration and Hb content continue to play a crucial role in the differential diagnosis of anemias 80 years after the publication of Wintrobe's seminal work. Modern hematology analyzers provide additional data on the heterogeneity of these parameters (distribution width) and quantify similar parameters of reticulocytes as well. Red cell and reticulocyte cellular indices are widely used in the diagnosis and monitoring of hematological diseases.

RECENT FINDINGS

Quantification of hypochromic cells is valuable in the differential diagnosis of thalassemia trait and iron deficiency, and in monitoring therapeutic response to erythropoietic stimulating agents, while hyperchromic cells are an essential diagnostic component for hereditary spherocytosis and may correlate with hemolytic parameters in sickle cell disease. Values for these parameters however depend on the technology used. Red cell clearance is associated with a reduction in both Hb content and cell volume: normal cells are likely to be removed by the time they reach a volume of 72 fl. Reticulocyte parameters such as Hb content (CHr or ret-He) or maturity index (RMI) have shown value in a variety of hematological conditions. New findings from genetic association studies have identified several potential novel genes affecting red cell indices, which are not mediated by changes in iron availability.

SUMMARY

Red cell indices continue to provide an essential support to the diagnosis and monitoring of hematological diseases.

Hereditary spherocytosis, elliptocytosis, and other red cell membrane disorders

Hereditary spherocytosis and elliptocytosis are the two most common inherited red cell membrane disorders resulting from mutations in genes encoding various red cell membrane and skeletal proteins. Red cell membrane, a composite structure composed of lipid bilayer linked to spectrin-based membrane skeleton is responsible for the unique features of flexibility and mechanical stability of the cell. Defects in various proteins involved in linking the lipid bilayer to membrane skeleton result in loss in membrane cohesion leading to surface area loss and hereditary spherocytosis while defects in proteins involved in lateral interactions of the spectrin-based skeleton lead to decreased mechanical stability, membrane fragmentation and hereditary elliptocytosis. The disease severity is primarily dependent on the extent of membrane surface area loss. Both these diseases can be readily diagnosed by various laboratory approaches that include red blood cell cytology, flow cytometry, ektacytometry, electrophoresis of the red cell membrane proteins, and mutational analysis of gene encoding red cell membrane proteins.

Hereditary red cell membrane disorders and laboratory diagnostic testing

This overview describes two groups of nonimmune hereditary hemolytic anemias caused by defects in membrane proteins located in distinct layers of the red cell membrane. Hereditary spherocytosis (HS), hereditary elliptocytosis (HE), and hereditary pyropoikilocytosis (HPP) represent disorders of the red cell cytoskeleton. Hereditary stomatocytoses represents disorders of cation permeability in the red cell membrane. The current laboratory screening tests for HS are the osmotic fragility test, acid glycerol lysis time test (AGLT), cryohemolysis test, and eosin-5'-maleimide (EMA)-binding test. For atypical HS, SDS-polyacrylamide gel electrophoresis of erythrocyte membrane proteins is carried out to confirm the diagnosis. The diagnosis of HE/HPP is based on abnormal red cell morphology and the detection of protein 4.1R deficiency or spectrin variants using gel electrophoresis. None of screening tests can detect all HS cases. Some testing centers (a survey of 25 laboratories) use a combination of tests (e.g., AGLT and EMA). No specific screening test for hereditary stomatocytoses is available. The preliminary diagnosis is based on presenting a compensated hemolytic anemia, macrocytosis, and a temperature or time dependent pseudohyperkalemia in some patients. Both the EMA-binding test and the osmotic fragility test may help in differential diagnosis of HS and hereditary stomatocytosis.

Erythrocyte membrane protein defects in hereditary spherocytosis patients in Turkish population

Hereditary spherocytosis (HS) is a congenital hemolytic anemia which is characterized by spherocytes in peripheral blood and increased osmotic fragility test. The disease is caused by defects in red cell membrane cytoskeleton. In this study, we investigated erythrocyte membrane protein defects in 50 Turkish HS patients and 42 controls. We used sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to identify the protein defects causing HS. The patients were from 27 families (39 kindred and 11 unrelated patients). They were aged between 6 months and 53 years and the mean age was 18.75 (±14.70) years. Protein deficiencies related to HS were demonstrated in 42% of study group. There was not any statistically significant relation between the protein deficiency and hemoglobin levels. Isolated or combined spectrin deficiency was the most common protein abnormality among our patients. Spectrin deficiency was detected in 22% of cases (11/50), ankyrin deficiency in 8% (4/50), protein 4.2 deficiency in 8% (4/50), combined spectrin and protein 4.2 deficiency in 2% (1/50), combined spectrin and ankyrin deficiency in 2% (1/50). Fifty-eight percent of cases (29/50) showed normal protein contents.

Comparative effectiveness of different types of splenectomy for children with congenital hemolytic anemias

OBJECTIVE

To compare the effectiveness of different types of splenectomy in children with congenital hemolytic anemias.

STUDY DESIGN

We constructed key questions that addressed outcomes relevant to clinicians and families on effects of partial or total splenectomy, including hematologic effect, splenic function, and the risk of adverse events. We identified from Pubmed and Embase 703 studies that evaluated different types of splenectomy and accepted 93 studies that satisfied entry criteria. We graded the quality of each report and summarized the overall strength of research evidence for each key question.

RESULTS

We did not identify any randomized clinical trials. All types of splenectomy have favorable clinical outcomes in most diseases. We did not identify any hematologic advantage of laparoscopy compared with laparotomy. Adverse events are uncommon in most studies and are minimized with use of laparoscopy.

CONCLUSIONS

There is a need for randomized clinical trials and improved data collection of different types of splenectomy in congenital hemolytic anemias. Outcomes studied should address the concerns of families and clinicians to assess the risks and benefits of various treatments.

Diagnostic power of laboratory tests for hereditary spherocytosis: a comparison study in 150 patients grouped according to molecular and clinical characteristics

BACKGROUND

The laboratory diagnosis of hereditary spherocytosis commonly relies on NaCl-based or glycerol-based red cell osmotic fragility tests; more recently, an assay directly targeting the hereditary spherocytosis molecular defect (eosin-5'-maleimide-binding test) has been proposed. None of the available tests identifies all cases of hereditary spherocytosis.

DESIGN AND METHODS

We compared the performances of the eosin-5'-maleimide-binding test, NaCl-osmotic fragility studies on fresh and incubated blood, the glycerol lysis test, the acidified glycerol lysis test, and the Pink test on a series of 150 patients with hereditary spherocytosis grouped according to clinical phenotype and the defective protein, with the final aim of finding the combination of tests associated with the highest diagnostic power, even in the mildest cases of hereditary spherocytosis.

RESULTS

The eosin-5'-maleimide-binding test had a sensitivity of 93% and a specificity of 98% for detecting hereditary spherocytosis: the sensitivity was independent of the type and amount of molecular defect and of the clinical phenotype. The acidified glycerol lysis test and Pink test showed comparable sensitivity (95% and 91%). The sensitivity of NaCl osmotic fragility tests, commonly considered the gold standard for the diagnosis of hereditary spherocytosis, was 68% on fresh blood and 81% on incubated blood, and further decreased in compensated cases (53% and 64%, respectively). The combination of the eosin-5'-maleimide-binding test and acidified glycerol lysis test enabled all patients with hereditary spherocytosis to be identified. The eosin-5'-maleimide-binding test showed the greatest disease specificity.

CONCLUSIONS

Each type of test fails to diagnose some cases of hereditary spherocytosis. The association of an eosin-5'-maleimide-binding test and an acidified glycerol lysis test enabled identification of all patients with hereditary spherocytosis in this series and, therefore, represents a currently effective diagnostic strategy for hereditary spherocytosis including mild/compensated cases.

Proteomic identification of erythrocyte membrane protein deficiency in hereditary spherocytosis

Hereditary spherocytosis (HS) is the most common congenital hemolytic anemia in Caucasians, with an estimated prevalence ranging from 1:2000 to 1:5000. The molecular defect in one of the erythrocytes (RBC) membrane proteins underlying HS like; spectrin-α, spectrin-β, ankyrin, band 3 and protein 4.2 that lead to membrane destabilization and vesiculation, may change the RBCs into denser and more rigid cells (spherocytes), which are removed by the spleen, leading to the development of hemolytic anemia. It is classified as mild, moderate and severe, according to the degree of the hemolytic anemia and the associated symptoms. Two-dimensional gel electrophoresis (2-DE) is potentially valuable method for studying heritable disorders as HS that involve membrane proteins. This separation technique of proteins based upon two biophysically unrelated parameters; molecular weight and charge, is a good option in clinical proteomics in terms of ability to separate complex mixtures, display post-translational modifications and changes after phosphorylation. In this study, we have used contemporary methods with some modifications for the solubilisation, separation and identification of erythrocyte membrane proteins in normal and in HS RBCs. Spectrin alpha and beta chain, ankyrin and band 3 proteins expression differences were found with PDQuest software 8.0.1. and peptide mass fingerprinting (PMF) analysis performed for identification of proteins in this study.

Additional erythrocytic and reticulocytic parameters helpful for diagnosis of hereditary spherocytosis: results of a multicentre study

Hereditary spherocytosis (HS) is characterised by weakened vertical linkages between the membrane skeleton and the red blood cell's lipid bilayer, leading to the release of microparticles. All the reference tests suffer from specific limitations. The aim of this study was to develop easy to use diagnostic tool for screening of hereditary spherocytosis based on routinely acquired haematological parameters like percentage of microcytes, percentage of hypochromic cells, reticulocyte counts, and percentage of immature reticulocytes. The levels of haemoglobin, mean cell volume, mean corpuscular haemoglobin concentration, reticulocytes (Ret), immature reticulocytes fraction (IRF), hypochromic erythrocytes (Hypo-He) and microcytic erythrocytes (MicroR) were determined on EDTA samples on Sysmex instruments from a cohort of 45 confirmed SH. The HS group was then compared with haemolytical disorders, microcytic anaemia, healthy individuals and routine samples (n = 1,488). HS is characterised by a high Ret count without an equally elevated IRF. All 45 HS have Ret >80,000/μl and Ret(10(9)/L)/IRF (%) greater than 7.7 (rule 1). Trait and mild HS had a Ret/IRF ratio greater than 19. Moderate and severe HS had increased MicroR and MicroR/Hypo-He (rule 2). Combination of both rules gave predictive positive value and negative predictive value of respectively 75% and 100% (n=1,488), which is much greater than single parameters or existing rules. This simple and fast diagnostic method could be used as an excellent screening tool for HS. It is also valid for mild HS, neonates and ABO incompatibilities and overcomes the lack of sensitivity of electrophoresis in ankyrin deficiencies.

A prospective study to assess the predictive value for hereditary spherocytosis using five laboratory tests (cryohemolysis test, eosin-5'-maleimide flow cytometry, osmotic fragility test, autohemolysis test, and SDS-PAGE) on 50 hereditary spherocytosis families in Argentina

This prospective study was carried out to assess the usefulness of five laboratory tests in the diagnosis of hereditary spherocytosis (HS), based on the correlation of erythrocyte membrane protein defects with clinical and laboratory features, and also to determine the membrane protein deficiencies detected in Argentina. Of 116 patients and their family members tested, 62 of them were diagnosed to have HS. The specificity of cryohemolysis (CH) test was 95.2%, and its cut-off value to distinguish HS from normal was 2.8%. For flow cytometry, cut-off points of 17% for mean channel fluorescence (MCF) decrease and 14% coefficient of variation (CV) increase showed 95.9% and 92.2% specificity, respectively. Both tests showed the highest percentages of positive results for diagnosis. Either CH or flow cytometry was positive in 93.5% of patients. In eight patients, flow cytometry was positive only through CV increase. Protein defects were detected in 72.3% of patients; ankyrin and spectrin were the most frequently found deficiencies. The CV of the fluorescence showed significantly higher increases in moderate and severe anemia than in mild anemia (p = 0.003). Severity of anemia showed no other correlation with tests results, type of deficient protein, inheritance pattern, or neonatal jaundice. CH and flow cytometry are easy methods with the highest diagnostic accuracy. Simultaneous reading of mean channel fluorescence (MCF) decrease and CV increase improve diagnostic usefulness of flow cytometry. This test seems to be a reliable predictor of severity. The type of detected protein deficiency has no predictive value for outcome. Predominant ankyrin and spectrin deficiencies agree with reports from other Latin American countries.

Stem cells--a source of adult red blood cells for transfusion purposes: present and future

We have sufficient knowledge of the biology of hematopoietic stem cells to hope that we might generate human red blood cells in the laboratory. It may soon be possible to produce enough to transfuse "cultured" red blood cells to manufacture human red blood cells from hematopoietic stem cells for transfusion purposes. This article describes progress and the challenges that remain in the search for in vitro generated red blood cells that can be efficiently manufactured in high volumes and given to any recipient.

Vascular complications after splenectomy for hematologic disorders

The most widely recognized long-term risk of splenectomy is overwhelming bacterial infection. More recently, thrombosis has become appreciated as another potential complication of the procedure. Because of these long-term risks, the indications for and timing of splenectomy are debated in the medical community. Accordingly, the adverse effects and benefits of splenectomy for hematologic disorders and other conditions demand further study. This comprehensive review summarizes the existing literature pertaining to vascular complications after splenectomy for hematologic conditions and attempts to define the potential pathophysiologic mechanisms involved. This complex topic encompasses diverse underlying conditions for which splenectomy is performed, diverse thrombotic complications, and multiple pathophysiologic mechanisms.