Experience with eosin-5'-maleimide as a diagnostic tool for red cell membrane cytoskeleton disorders

Diagnostic yield of targeted next-generation sequencing for pediatric hereditary hemolytic anemia

BACKGROUND

Hereditary hemolytic anemia (HHA) refers to a heterogeneous group of genetic disorders that share one common feature: destruction of circulating red blood cells (RBCs). The destruction of RBCs may be due to membranopathies, enzymopathies, or hemoglobinopathies. Because these are genetic disorders, incorporation of next-generation sequencing (NGS) has facilitated the diagnostic process of HHA.

METHOD

Genetic data from 29 patients with suspected hereditary anemia in a tertiary hospital were retrospectively reviewed to evaluate the efficacy of NGS on hereditary anemia diagnosis. Targeted NGS was performed with custom probes for 497 genes associated with hematologic disorders. After genomic DNA was extracted from peripheral blood, prepared libraries were hybridized with capture probes and sequenced using NextSeq 550Dx (Illumina, San Diego, CA, USA).

RESULT

Among the 29 patients, ANK1 variants were detected in five, four of which were pathogenic or likely pathogenic variants. SPTB variants were detected in six patients, five of which were classified as pathogenic or likely pathogenic variants. We detected g6pd pathogenic and spta1 likely pathogenic variants in two patients and one patient, respectively. Whole-gene deletions in both HBA1 and HBA2 were detected in two patients, while only HBA2 deletion was detected in one patient. One likely pathogenic variant in PLKR was detected in one patient, and one likely pathogenic variant in ALAS2 was detected in another.

CONCLUSION

Here, NGS played a critical role in definitive diagnosis in 18 out of 29 patients (62.07%) with suspected HHA. Thus, its incorporation into the diagnostic workflow is crucial.

Development of High-Resolution Melting Curve Analysis for rapid detection of SEC23B gene mutation causing Congenital Dyserythropoietic Anemia type II in Indian population

BACKGROUND

Congenital dyserythropoietic anemias (CDAs) are a very rare and heterogeneous group of disorders characterized by ineffective erythropoiesis. CDA II is caused by mutations in the SEC23B gene. The most common mutation reported in India is c.1385 A > G, p.Y462C. There is no simple and cost-effective confirmatory diagnostic test available for CDA, and therefore, many patients remain undiagnosed. High-resolution melting curve (HRM) analysis is a polymerase chain reaction (PCR) based technique applied to identify genetic differences and scan nucleic acid sequences. HRM can be used to rapidly screen the common mutation causing CDA II in the Indian population. Thus, we studied the use of High-Resolution Melting Curve Analysis to detect common mutation causing CDA II in the Indian population.

METHOD

11 patients having SEC23B (Y462C) mutation causing CDA II are considered for this study. HRM was used to check the presence of Y462C mutation. To verify the accuracy of the HRM analysis, we compared HRM results with the results of Sanger sequencing. This helped us to confirm the diagnosis.

RESULTS

We have described the clinical, hematological, and genetic data of eleven patients suffering from CDAII. According to HRM and Sanger sequencing, a homozygous SEC23B (Y462C) mutation was present in all patients, whereas a heterozygous Y462C mutation was present in their parents.

CONCLUSION

Our data showed that High-Resolution Melting (HRM) analysis could be used to rapidly screen common SEC23B mutation that causes CDA II in the Indian population.

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.

Targeted next-generation sequencing revealed a novel homozygous mutation in the LRBA gene causes severe haemolysis associated with Inborn Errors of Immunity in an Indian family

OBJECTIVES

LPS-responsive beige-like anchor protein (LRBA) deficiency abolishes LRBA protein expression due to biallelic mutations in the LRBA gene that lead to autoimmune manifestations, inflammatory bowel disease, hypogammaglobulinemia in early stages, and variable clinical manifestations.

MATERIALS AND METHODS

Mutational analysis of the LRBA gene was performed in Indian patients using targeted Next Generation Sequencing (t-NGS) and confirmed by Sanger sequencing using specific primers of exons 53. Then, bioinformatics analysis and protein modeling for the novel founded mutations were also performed. The genotype, phenotype correlation was done according to the molecular findings and clinical features.

RESULTS

We report an unusual case of a female patient born of a consanguineous marriage, presented with severe anaemia and jaundice with a history of multiple blood transfusions of unknown cause up to the age of 5 yrs. She had hepatosplenomegaly with recurrent viral and bacterial infections. Tests for hemoglobinopathies, enzymopathies, and hereditary spherocytosis were within the normal limits. The t-NGS revealed a novel homozygous missense variation in exon 53 of the LRBA gene (chr4:151231464C > T; c.7799G > A) (p.C2600Y), and the parents were heterozygous. The further immunological analysis is suggestive of hypogammaglobulinaemia and autoimmune haemolytic anaemia. The bioinformatics tools are suggestive of deleterious and disease-causing variants.

CONCLUSION

This study concludes the importance of a timely decision of targeted exome sequencing for the molecular diagnostic tool of unexplained haemolytic anaemia with heterogeneous clinical phenotypes.

Comparison of a modified flow cytometry osmotic fragility test with the classical method for the diagnosis of hereditary spherocytosis

BACKGROUND

Hereditary spherocytosis (HS) is the most common inherited hemolytic anemia. The flow cytometric test using eosin-5'maleimide (EMA) is a well-established diagnostic method. However, in order to improve HS detection, it is recommended that EMA and an osmotic fragility test (OFT) both be performed. OFT is time consuming and labor intensive. We used a flow cytometric (FOFT) adaptation of the classical OFT reported by Yamamoto. We compare the FOFT to the classical OFT including practical data and propose options for simplifying this method.

METHODS

Suspected and known HS patients and controls were tested by the following methods: EMA, OFT, and FOFT including some modifications.

RESULTS

The FOFT method is robust and correlates to loss of red blood cells. OFT and FOFT gave similar results in healthy controls and four HS patients. Normal range for FOFT in 70 adults is shown and can be used as a reference value. Neonates should have their own normal range defined. Overnight sample incubation at 37°C did not add information to the FOFT results.

CONCLUSION

Our modified Yamomoto FOFT can replace the classic OFT as the addition to EMA for the diagnosis of HS. The use of flow cytometry in both these methods requires small sample volume, is reproducible, simpler, and produces results more rapidly.

Alectinib induces marked red cell spheroacanthocytosis in a near-ubiquitous fashion and is associated with reduced eosin-5-maleimide binding

We reviewed haematological investigations for 43 patients treated at a single centre with alectinib, an inhibitor of anaplastic lymphoma kinase (ALK) which is considered standard first-line treatment for patients with ALK-rearranged advanced non-small cell lung cancer. Ninety-five percent of patients developed marked acanthocytosis, echinocytosis and/or spheroacanthocytosis, not observable with prior treatment with other ALK-inhibitors. Anaemia developed in 73% of patients (38% <100 g/L, 8% <80 g/L), though definite new haemolysis was present in only 11%. Eosin-5-maleimide binding was reduced in all assessed patients, and increased membrane cholesterol was identified in one patient assessed with lattice light sheet microscopy. We have identified a previously undescribed phenomenon whereby alectinib induces red cell membrane abnormalities in nearly all patients through an unclear, but likely ALK-independent, mechanism, resulting in mild anaemia without universal haemolysis.

Novel pathogenic variant c.2714C>A (p. Thr905Lys) in the HK1 gene causing severe haemolytic anaemia with developmental delay in an Indian family

Hexokinase (EC 2.7.1.1, Adenosine Tri Phosphate (ATP): D-hexose-6-phosphotransferase) is a crucial regulatory enzyme of the glycolytic pathway (Embden-Meyerhof pathway). Hexokinase deficiency is associated with chronic non-spherocytic haemolytic anaemia (HA) with some exceptional cases showing psychomotor/mental retardation and fetus death. The proband is a four-and-half-year-old female child born of a four-degree consanguineous marriage hailing from South India with autosomal recessive congenital HA associated with developmental delay. She was well till 3 months of her age post an episode of diarrhoea when she was noted to be severely anaemic and requiring regular transfusions. The common causes of HA, haemoglobinopathies, red cell membranopathies and common red cell enzymopathies (G6PD, GPI, PK and P5N) were ruled out. Targeted analysis of whole exome sequencing (WES) using an insilico gene panel for hereditary anaemia was performed to identify pathogenic variants in the patient. Next-generation sequencing revealed a novel homozygous variant in hexokinase gene c.2714C>A (p. Thr905Lys) in exon-18. The pathogenic nature of the variant p. Thr905Lys in the HK1 gene was confirmed collectively by biochemical and molecular studies. Insilico analysis (PolyPhen-2, Provean, Mutation Taster) predicted the variant to be severe disease causing. Multiple sequence alignment demonstrated the conservation of p. Thr905 across the species. The impact of the mutation on the protein structure was studied by PyMOL and Swiss Protein databank viewer.

Genotypic analysis of SLC4A1 A858D mutation in Indian population associated with distal renal tubular Acidosis (dRTA) coupled with hemolytic anemia

INTRODUCTION

Although distinctive, distal renal tubular acidosis (dRTA) and Hereditary Spherocytosis (HS) shares a common protein, the anion exchanger1 (AE1) encoded by SLC4A1gene. In spite of this, the co-existence of dRTA and HS has rarely been observed. To date, 23 mutations have been identified in SLC4A1 gene causing both autosomal recessive (AR) and autosomal dominant (AD) forms of dRTA.

METHODS

We have assessed the applicability of the High Resolution Melting curve (HRM) method for the detection of SLC4A1 (A858D) mutation in 12 Indian families having AR dRTA coupled with HS. The reliability of the HRM analysis was verified by comparing the results of the HRM method with those of conventional methods such as Polymerase Chain Reaction-Restriction Fragment-Length Polymorphism (PCR-RFLP) and Sanger sequencing thereby confirming the diagnosis.

RESULTS

We here described the clinical, hematological and genetic data of 16 individuals from 12 families having AR dRTA coupled with HS. All patients carried homozygous SLC4A1 (A858D) mutation, whereas their family members had heterozygous A858D obtained by HRM analysis and confirmed by RFLP and Sanger sequencing.

CONCLUSION

Our data indicates that a missense mutation of A858D in SLC4A1 gene is the most common cause of dRTA coupled with HS in the Indian population. HRM analysis can be used as a rapid screening method for common SLC4A1 mutations that cause AR dRTA in the Indian population.

A clinical and experimental study of adult hereditary spherocytosis in the Chinese population

Hereditary spherocytosis (HS) is often misdiagnosed due to lack of specific diagnostic methods. Our study summarized clinical characteristics and described the diagnostic workflow for mild and moderate HS in Chinese individuals, using data from 20 adults, 8 of whom presented a familial history for HS. We used scanning electron microscopy (SEM) to diagnose HS. We observed reduced eosin maleimide fluorescence activity (5.50 mean channel fluorescence (MCF) units) in the 10 cases of HS, which differed significantly when compared with 10 normal adults (15.50 units), iron deficiency anemia (15.50 MCF units), and megaloblastic anemia (12.00 MCF units) values (P < .05). Next generation sequencing results revealed that 9 out of 10 patients were found to have mutations in the spectrin alpha chain (SPTB), anchor protein (ANK1), and SLC4A1 genes. These mutations were not reported in the Human Gene Mutation Database (HGMD), 1000 human genome, ExAC, and dbSNP147 databases. Splenectomy proved to be beneficial in alleviating HS symptoms in 10 cases. It was found that for the diagnosis of HS, SEM and next generation gene sequencing method proved to be more ideal than red blood cell membrane protein analysis using sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blotting.

Mechanosensitive Piezo1 ion channel protein (PIEZO1 gene): update and extended mutation analysis of hereditary xerocytosis in India

Hereditary xerocytosis (HX), also known as dehydrated stomatocytosis (DHSt) is a dominantly inherited genetic disorder exhibiting red cell membrane dehydration caused by the loss of the monovalent cation K⁺ and water. Variants in mechanosensitive Piezo ionic channels of the PIEZO1 gene are the primary cause of HX. We have utilized high throughput and highly precise next-generation sequencing (NGS) to make a diagnosis and examine the genotype-phenotype relationship in inflexible HX cases. Seven unrelated patients with unexplained hemolytic anemia were scrutinized with a panel probing 8000 genes related to congenital anemia. Targeted next-generation sequencing identified 8 missense variants in the PIEZO1 gene in 7 unrelated Indian patients. Three of the 8 variants are novel (c.1795G > C, c.2915G > A, c.7372 T > C) and the remaining five (c.4082A > G, c.6829C > A, c.7374C > G, c.7381G > A, c.7483_7488dup) are previously reported. The variants have been validated by Sanger sequencing. One patient with autosomal dominant mutation (c.7372 T > C) is associated with iron refractory iron deficiency anemia. Of the 7 patients, one has HX in combination with a novel homozygous variant (c.994G > A) in the PKLR gene causing PK deficiency resulting in severe clinical manifestations with phenotypic variability. In silico prediction using bioinformatics tools were used to study the possible damaging effects of the novel variants. Structural-functional analysis of the novel variants was investigated by molecular modeling software (PyMOL and Swiss PDB). These results encompass the heterogeneous behavior of mechano-sensitive Piezo1 protein observed in HX patients in India. Moreover, NGS imparted a subtle, economical, and quick tool for understanding the genetic cause of undiagnosed cases of congenital hemolytic anemia. NGS grants a potential technology integrating clinical history together with molecular report profiting in such patients and their families.

Laboratory Approach to Hemolytic Anemia

Hemolytic anemias are a group of disorders with varied clinical and molecular heterogeneity. They are characterized by decreased levels of circulating erythrocytes in blood. The pathognomic finding is a reduced red cell life span with severe anemia or, compensated hemolysis accompanied by reticulocytosis. The diagnostic workup or laboratory approach for hemolytic anemias is based on methodical step-wise testing which includes red blood cell morphology, hematological indices with increased reticulocyte count along with clinical features of hemolytic anemias. If conventional laboratory tests are unable to detect the underlying cause of hemolysis, genetic testing is recommended. Sanger sequencing along with conventional testing is the most efficient way to diagnose the underlying genetic causes, especially in thalassemias/hemoglobinopathies, if required. However, hemolytic anemias being highly heterogeneous disorders, next-generation sequencing-based screening is rapidly becoming an efficient way to decipher the etiologies where common causes have been excluded.

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.

Study of pathophysiology and molecular characterization of congenital anemia in India using targeted next-generation sequencing approach

Most patients with anemia are diagnosed through clinical phenotype and basic laboratory testing. Nonetheless, in cases of rare congenital anemias, some patients remain undiagnosed despite undergoing an exhaustive workup. Genetic testing is complicated by the large number of genes that are involved in rare anemias, due to similarities in the clinical presentation. We sought to enhance the diagnosis of patients with congenital anemias by using targeted next-generation sequencing. The genetic diagnosis was performed by gene capture followed by next-generation sequencing of 76 genes known to cause anemia syndromes. Genetic diagnosis was achieved in 17 of 21 transfusion-dependent patients and undiagnosed by conventional workup. Four cases were diagnosed with red cell membrane protein defects, four patients were diagnosed with pyruvate kinase deficiency, one case of adenylate kinase deficiency, one case of glucose phosphate isomerase deficiency, one case of hereditary xerocytosis, three cases having combined membrane and enzyme defect, two cases with Diamond-Blackfan anemia (DBA) and 1 with CDA type II with 26 different mutations, of which 21 are novel. Earlier incorporation of this NGS method into the workup of patients with congenital anemia may improve patient care and enable genetic counselling.

Flow Cytometric Test with Eosin-5-Maleimide for a Diagnosis of Hereditary Spherocytosis in a Newborn

A term male newborn born to a mother who had hereditary spherocytosis presented with neonatal jaundice at 20 hours of life. Complete blood count showed hemoglobin 17.1 g/dL, MCV 104.2 fL, MCH 32.9 pg, and MCHC 31.6 g/dL. The patient had indirect hyperbilirubinemia requiring phototherapy. The maximum total bilirubin level was 12.15 mg/dL at 20 hours of life. Peripheral blood smear revealed spherocytes, crenated red cells, and polychromasia. A flow cytometric test with eosin-5-maleimide- (EMA-) labeled RBC was performed in the patient and parents. The fluorescence histograms of EMA-labeled RBC from the patient and mother were shifted to the left, and the fluorescence ratio when compared with normal was 0.69 and 0.84, respectively. The flow cytometric test with EMA is useful in supporting the diagnosis of hereditary spherocytosis during newborn period.

Red cell adenylate kinase deficiency in India: identification of two novel missense mutations (c.71A>G and c.413G>A)

Adenylate kinase (AK) deficiency is a rare erythroenzymopathy associated with hereditary nonspherocytic haemolytic anaemia along with mental/psychomotor retardation in few cases. Diagnosis of AK deficiency depends on the decreased level of enzyme activity in red cell and identification of a mutation in the AK1 gene. Until, only eight mutations causing AK deficiency have been reported in the literature. We are reporting two novel missense mutation (c.71A > G and c.413G > A) detected in the AK1 gene by next-generation sequencing (NGS) in a 6-year-old male child from India. Red cell AK enzyme activity was found to be 30% normal. We have screened a total of 32 family members of the patient and showed reduced red cell enzyme activity and confirm mutations by Sanger's sequencing. On the basis of Sanger sequencing, we suggest that the proband has inherited a mutation in AK1 gene exon 4 c.71A > G (p.Gln24Arg) from paternal family and exon 6 c.413G > A (p.Arg138His) from maternal family. Bioinformatics tools, such as SIFT, Polymorphism Phenotyping v.2, Mutation Taster, MutPred, also confirmed the deleterious effect of both the mutations. Molecular modelling suggests that the structural changes induced by p.Gln24Arg and p.Arg138His are pathogenic variants having a direct impact on the structural arrangement of the region close to the active site of the enzyme. In conclusion, NGS will be the best solution for diagnosis of very rare disorders leading to better management of the disease. This is the first report of the red cell AK deficiency from the Indian population.

Conjugate of Doxorubicin to Albumin-Binding Peptide Outperforms Aldoxorubicin

Short circulation time and off-target toxicity are the main challenges faced by small-molecule chemotherapeutics. To overcome these shortcomings, an albumin-binding peptide conjugate of chemotherapeutics is developed that binds specifically to endogenous albumin and harnesses its favorable pharmacokinetics and pharmacodynamics for drug delivery to tumors. A protein-G-derived albumin-binding domain (ABD) is conjugated with doxorubicin (Dox) via a pH-sensitive linker. One to two Dox molecules are conjugated to ABD without loss of aqueous solubility. The albumin-binding ABD-Dox conjugate exhibits nanomolar affinity for human and mouse albumin, and upon administration in mice, shows a plasma half-life of 29.4 h, which is close to that of mouse albumin. Additionally, 2 h after administration, ABD-Dox exhibits an approximately 4-fold higher concentration in the tumor than free Dox. Free Dox clears quickly from the tumor, while ABD-Dox maintains a steady concentration in the tumor for at least 72 h, so that its relative accumulation at 72 h is ≈120-fold greater than that of free Dox. The improved pharmacokinetics and biodistribution of ABD-Dox result in enhanced therapeutic efficacy in syngeneic C26 colon carcinoma and MIA PaCa-2 pancreatic tumor xenografts, compared with free Dox and aldoxorubicin, an albumin-reactive Dox prodrug currently in clinical development.

Anemias raras y fallos medulares hereditarios

Las anemias raras y los fallos medulares hereditarios son enfermedades hematológicas caracterizadas, respectivamente, por una disminución de la concentración de hemoglobina o por diversos grados de defectos en la producción de células hematopoyéticas que conducen desde una citopenia de un solo linaje hasta una de múltiples linajes. Son enfermedades raras y difíciles de diagnosticar debido a la heterogeneidad clínica, citológica y genética. En este artículo abordaremos en primer lugar el diagnóstico de las anemias raras y sus causas principales: fallos medulares, defectos del hematíe y trastornos del metabolismo de los factores de maduración eritrocitario. Seguidamente introduciremos los fallos medulares hereditarios y su patología asociada, como son las malformaciones congénitas y la predisposición tumoral, haciendo especial hincapié en los más frecuentes: la anemia de Fanconi, la disqueratosis congénitca, la anemia de Diamond-Blackfan y el síndrome de Shwachman-Diamond.

Effect of inherited red cell defects on growth of Plasmodium falciparum: An in vitro study

Background & objectives:

High prevalence of certain polymorphic alleles of erythrocytes in malaria endemic area has been linked to the resistance provided by these alleles against parasitic infestations. Numerous studies undertaken to demonstrate this correlation have generated conflicting results. This study was undertaken to investigate the abilities of various polymorphic erythrocytes to support in vitro growth of Plasmodium falciparum parasites.

Methods:

In this study under in vitro condition the ability of P. falciparum parasites to grow was assessed in the erythrocytes obtained from a total of 40 patients with various haemoglobinopathies, such as β-thalassaemia (β-Thal), sickle cell anaemia, erythroenzymopathy-like glucose-6-phosphate dehydrogenase deficiency and membranopathy-like hereditary spherocytosis.

Results:

Significantly reduced in vitro invasion and growth of parasites was seen in the cultures containing abnormal erythrocytes than in control cultures containing normal erythrocytes (P< 0.05). The mean per cent parasitaemia comparison was also carried out among the three polymorphic erythrocyte groups, i.e. β-Thal, sickle cell anaemia and enzyme-membranopathies.

Interpretation & conclusions:

Erythroenzymopathies and membranopathies were found to provide a more hostile environment for parasites, as the least parasitaemia was observed in these erythrocytes. The present in vitro study showed that P. falciparum did not grow well and did not invade well in erythrocytes obtained from common inherited red cell disorders.

Flow Cytometric Eosin-5'-Maleimide Test is a Sensitive Screen for Hereditary Spherocytosis

Hereditary spherocytosis (HS) is a clinically heterogeneous disease characterized by mild to moderate hemolysis resulting from red cell membrane protein defects. Diagnostic tests include hemogram, reticulocyte count and blood smear evaluation, osmotic fragility, cryohemolysis, SDS-PAGE, flow cytometry using eosin-5'-maleimide (EMA) and genetic studies. We evaluated the flow cytometric EMA-binding test and compared it with osmotic fragility in 51 consecutive cases of suspected HS aged between 10 days and 62 years. In addition, 4 cases suspected on blood smears underwent EMA testing alone. The 16 EMA-positive cases who were determined to have HS had overlapping hemoglobin levels and reticulocyte counts with the 35 patients with normal EMA results, highlighting the importance of the flow cytometric test in providing a definitive diagnosis. Flow cytometric EMA binding test was thus a simple and relatively faster method to confirm HS in our experience.

Synergistic Integration of Laboratory and Numerical Approaches in Studies of the Biomechanics of Diseased Red Blood Cells

In red blood cell (RBC) disorders, such as sickle cell disease, hereditary spherocytosis, and diabetes, alterations to the size and shape of RBCs due to either mutations of RBC proteins or changes to the extracellular environment, lead to compromised cell deformability, impaired cell stability, and increased propensity to aggregate. Numerous laboratory approaches have been implemented to elucidate the pathogenesis of RBC disorders. Concurrently, computational RBC models have been developed to simulate the dynamics of RBCs under physiological and pathological conditions. In this work, we review recent laboratory and computational studies of disordered RBCs. Distinguished from previous reviews, we emphasize how experimental techniques and computational modeling can be synergically integrated to improve the understanding of the pathophysiology of hematological disorders.

Tokyo-1 Mutation: Hereditary Spherocytosis in a Hispanic Newborn Presenting as Early Onset Severe Hyperbilirubinemia

BACKGROUND

Hereditary spherocytosis in the Hispanic population does not often present with severe hyperbilirubinemia. Spectrin and band 3 mutations are most frequent in this population.

CASE REPORT

We present a Hispanic full-term female newborn with early onset significant hyperbilirubinemia without a history of familial hemolytic disorders. She was diagnosed with hereditary spherocytosis based on laboratory findings, including presence of spherocytes on a peripheral smear, and was later found by next-generation sequencing to have Tokyo-1 mutation, an ANK1 gene mutation, that was previously only reported in Japanese population.

CONCLUSION

Our report adds to the currently limited literature of the genetic spectrum and characteristics of hereditary spherocytosis in the Hispanic population. The absence of a positive family history does not preclude hereditary spherocytosis as a differential for pathologic neonatal hyperbilirubinemia.

Advances in laboratory diagnosis of hereditary spherocytosis

Among the red cell membrane disorders, hereditary spherocytosis (HS) is one of the most common causes of inherited hemolytic anemia. HS results from the deficiency or dysfunction of red blood cell membrane proteins, such as α spectrin, β spectrin, ankyrin, anion channel protein (Band-3 protein), protein 4.1 and protein 4.2. Conventionally, HS diagnosis is established through a series of tests, which include spherocytes identification in peripheral smear, reticulocyte count, osmotic fragility, etc. Currently, different hematological analyzers provide erythrocyte indicators that estimate the presence of spherocytes and correlate that with HS, which can be useful for disease screening. The most traditional method is the osmotic fragility (OF) test, which is labor-intensive and time-consuming to perform and presents low sensitivity and specificity values. Thus, new methods have been developed for HS diagnosis, such as flow cytometry. Current guidelines recommend the use of flow cytometry as a screening test for HS diagnosis using the eosin-5′-maleimide (EMA) binding test. Thus, HS diagnosis is the result of a collaboration between clinicians and laboratories, who should take into account the family history and the exclusion of other causes of secondary spherocytosis.

Improved harmonization of eosin-5-maleimide binding test across different instruments and age groups

BACKGROUND

The eosin-5'maleimide (EMA) binding test has been studied extensively for the detection of hereditary spherocytosis (HS). Its performance characteristics have been compared to NaCl-based or glycerol lysis-based red cell osmotic fragility tests and cryohemolysis. HS samples are also better identified when both mean channel fluorescence (MCF) of EMA relative to controls and the coefficient of variation (CV) are analyzed.

METHODS

We looked at 65 normal controls including 30 adults 25-65 years old and 35 newborns and 12 HS cases. In addition to the MCF and the CV, we used a side scatter (SSC) vs. EMA fluorescence gate or "footprint" to depict where normal erythrocytes should appear. Erythrocytes that have reduced band 3 protein appear outside of the footprint.

RESULTS

In our study, newborn data did not cluster with the samples from working age individuals. The MCF and the CVs of normal newborns were higher than normal adult group. However, the footprint data of normal samples relative to their controls was around 99.5% for each group, because the footprint was moved to fit the pattern of the normal.

CONCLUSIONS

The inclusion of footprint parameter will help in better standardization as well as implementation of this test across different age groups as well as different instruments. © 2015 International Clinical Cytometry Society.

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.

Stability of eosin-5'-maleimide dye used in flow cytometric analysis for red cell membrane disorders

Background

The eosin-5'-maleimide (EMA) binding test using flow cytometry is a common method to measure reduced mean channel fluorescence (MCF) of EMA-labeled red blood cells (RBCs) from patients with red cell membrane disorders. The basic principle of the EMA-RBC binding test involves the covalent binding of EMA to lysine-430 on the first extracellular loop of band 3 protein.

Methods

In the present study, the MCF of EMA was analyzed for samples derived from 12 healthy volunteers (controls) to determine the stability (i.e., the percentage decrease in fluorescence) of EMA over a period of 1 year.

Results

Comparison of periodical MCF readings over time, that is, at 2-month intervals, showed that there were no significant changes in mean channel fluorescence for up to 6 months; however, there was a significant decrease in MCF at 8 months.

Conclusion

For optimal dye utilization, EMA remained stable only for up to 6 months. Therefore, we recommend reconstitution of the dye every 6 months when implementing this test and storage at -80℃ in dark conditions.

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

OBJECTIVE

To investigate the sensitivity and specificity of eosin-5'-maleimide (EMA)assay for the diagnosis of hereditary spherocytosis (HS), and to verify the stability of reagent and samples.

METHODS

EMA flow cytometry test, NaCl-osmotic fragility test and acidified glycerol lysis test were performed using peripheral blood samples from 80 patients with HS and 44 patients with other blood diseases, the sensitivity and specificity of the three methods were compared, and the feasibility of EMA binding test was estimated. The stability of EMA reagent and HS samples stored at different temperatures were tested.

RESULTS

Among the 124 tested samples, the sensitivity and specificity of EMA binding test was 0.925 and 0.954, that of NaCl-osmotic fragility test was 0.950 and 0.455, and that of acidified glycerol lysis test was 1.000 and 0.318, respectively. Although the sensitivity of NaCl-osmotic fragility test and acidified glycerol lysis test was a little higher than that of EMA binding test, the specificity of the former two methods was poor, they couldn't clearly distinguish whether spherocytosis is hereditary spherocytosis. The experiment results showed that EMA was sensitive to the temperature and should not be stored in a small aliquots at -80 ℃ over a period of 6 months. The stability of the HS sample was better, 6 days storage at 4 ℃ and 3 days storage at room temperature had no influence on the results.

CONCLUSION

EMA binding test by flow cytometry showed good sensitivity and specificity for HS diagnosis. EMA reagent should be stored at-80 ℃ and the HS samples should be tested within 6 days storage at 4 ℃ and 3 days at room temperature.

Particle Simulation of Oxidation Induced Band 3 Clustering in Human Erythrocytes

Oxidative stress mediated clustering of membrane protein band 3 plays an essential role in the clearance of damaged and aged red blood cells (RBCs) from the circulation. While a number of previous experimental studies have observed changes in band 3 distribution after oxidative treatment, the details of how these clusters are formed and how their properties change under different conditions have remained poorly understood. To address these issues, a framework that enables the simultaneous monitoring of the temporal and spatial changes following oxidation is needed. In this study, we established a novel simulation strategy that incorporates deterministic and stochastic reactions with particle reaction-diffusion processes, to model band 3 cluster formation at single molecule resolution. By integrating a kinetic model of RBC antioxidant metabolism with a model of band 3 diffusion, we developed a model that reproduces the time-dependent changes of glutathione and clustered band 3 levels, as well as band 3 distribution during oxidative treatment, observed in prior studies. We predicted that cluster formation is largely dependent on fast reverse reaction rates, strong affinity between clustering molecules, and irreversible hemichrome binding. We further predicted that under repeated oxidative perturbations, clusters tended to progressively grow and shift towards an irreversible state. Application of our model to simulate oxidation in RBCs with cytoskeletal deficiency also suggested that oxidation leads to more enhanced clustering compared to healthy RBCs. Taken together, our model enables the prediction of band 3 spatio-temporal profiles under various situations, thus providing valuable insights to potentially aid understanding mechanisms for removing senescent and premature RBCs.

In order to maintain a steady internal environment, our bodies must be able to specifically recognize old and damaged red blood cells (RBCs), and remove them from the circulation in a timely manner. Clusters of membrane protein band 3, which form in response to elevated oxidative damage, serve as essential molecular markers that initiate this cell removal process. However, little is known about the details of how these clusters are formed and how their properties change under different conditions. To understand these mechanisms in detail, we developed a computational model that enables the prediction of the time course profiles of metabolic intermediates, as well as the visualization of the resulting band 3 distribution during oxidative treatment. Our model predictions were in good agreement with previous published experimental data, and provided predictive insights on the key factors of cluster formation. Furthermore, simulation experiments of the effects of multiple oxidative pulses and cytoskeletal defect using the model also suggested that clustering is enhanced under such conditions. Analyses using our model can provide hypotheses and suggest experiments to aid the understanding of the physiology of anemia-associated RBC disorders, and optimization of quality control of RBCs in stored blood.

Evaluating eosin-5-maleimide binding as a diagnostic test for hereditary spherocytosis in newborn infants

OBJECTIVE

Neonates with undiagnosed hereditary spherocytosis (HS) are at risk for developing hazardous hyperbilirubinemia and anemia. Making an early diagnosis of HS in a neonate can prompt anticipatory guidance to prevent these adverse outcomes. A recent comparison study showed that a relatively new diagnostic test for HS, eosin-5-maleimide (EMA)-flow cytometry, performs better than other available tests in confirming HS. However, reports have not specifically examined the performance of this test among neonates.

STUDY DESIGN

We compared EMA-flow cytometry from blood samples of healthy control neonates vs samples from neonates suspected of having HS on the basis of severe Coombs-negative jaundice and spherocytes on blood film. The diagnosis of HS was later either confirmed or excluded based on clinical findings and next generation sequencing (NGS) after which we correlated the EMA-flow results with the diagnosis.

RESULT

EMA-flow was performed on the blood of 31 neonates; 20 healthy term newborns and 11 who were suspected of having HS. Eight of the 11 were later confirmed positive for HS and one was confirmed positive for hereditary elliptocytosis (HE). All nine had persistently abnormal erythroid morphology, reticulocytosis and anemia, and eight of the nine had relevant mutations discovered using NGS. The other was confirmed positive for HS on the basis that a parent had HS, and the neonate's spherocytosis, reticulocytosis and anemia persisted. The 20 healthy controls and the 2 in whom HS was initially suspected but later excluded all had EMA-flow results in the range reported in healthy children and adults. In contrast, all nine in whom HS or HE was confirmed had abnormal EMA-flow results consistent with previous reports in older children and adults with HS.

CONCLUSION

Although our sample size is small, our findings are consistent with the literature in older children and adults suggesting that EMA-flow cytometric testing performs well in supporting the diagnosis of HS/HE during the early neonatal period.

Comparison study of the eosin-5'-maleimide binding test, flow cytometric osmotic fragility test, and cryohemolysis test in the diagnosis of hereditary spherocytosis

OBJECTIVES

Current guidelines recommend the eosin-5'-maleimide (EMA) binding test and cryohemolysis test for screening for hereditary spherocytosis (HS), and the flow cytometric osmotic fragility (FC OF) test was recently developed to replace the classic OF test. We evaluatedthe performance of the EMA binding test, FC OF test, cryohemolysis test, and the hemoglobin (Hb)/mean corpuscular hemoglobin concentration (MCHC) ratio in the diagnosis of HS and assessed whether these tests reflect the clinical severity of HS.

METHODS

A total of 153 patients with anemia (33 with HS, 40 with autoimmune hemolytic anemia, 40 with anemia of chronic disease, and 40 with iron deficiency anemia [IDA]) and 140 healthy controls were enrolled, and the performance of the three tests was evaluated.

RESULTS

Both the EMA binding test (area under the curve [AUC], 0.996) and the FC OF test (AUC, 0.992) performed satisfactorily, but the cryohemolysis test (AUC, 0.723) performed significantly worse because of false positivity in patients with IDA. The Hb/MCHC ratio (P < .001) was able to reflect the clinical severity of HS.

CONCLUSIONS

Our results demonstrate that both the EMA binding and FC OF tests are useful as screening tests for the diagnosis of HS, but the cryohemolysis test has limited use due to its false positivity in IDA, with the Hb/MCHC ratio the most useful parameter for assessing the clinical severity of HS.

Characterization of ENU-induced Mutations in Red Blood Cell Structural Proteins

Murine models with modified gene function as a result of N-ethyl-N-nitrosourea (ENU) mutagenesis have been used to study phenotypes resulting from genetic change. This study investigated genetic factors associated with red blood cell (RBC) physiology and structural integrity that may impact on blood component storage and transfusion outcome. Forward and reverse genetic approaches were employed with pedigrees of ENU-treated mice using a homozygous recessive breeding strategy. In a "forward genetic" approach, pedigree selection was based upon identification of an altered phenotype followed by exome sequencing to identify a causative mutation. In a second strategy, a "reverse genetic" approach based on selection of pedigrees with mutations in genes of interest was utilised and, following breeding to homozygosity, phenotype assessed. Thirty-three pedigrees were screened by the forward genetic approach. One pedigree demonstrated reticulocytosis, microcytic anaemia and thrombocytosis. Exome sequencing revealed a novel single nucleotide variation (SNV) in Ank1 encoding the RBC structural protein ankyrin-1 and the pedigree was designated Ank1(EX34). The reticulocytosis and microcytic anaemia observed in the Ank1(EX34) pedigree were similar to clinical features of hereditary spherocytosis in humans. For the reverse genetic approach three pedigrees with different point mutations in Spnb1 encoding RBC protein spectrin-1β, and one pedigree with a mutation in Epb4.1, encoding band 4.1 were selected for study. When bred to homozygosity two of the spectrin-1β pedigrees (a, b) demonstrated increased RBC count, haemoglobin (Hb) and haematocrit (HCT). The third Spnb1 mutation (spectrin-1β c) and mutation in Epb4.1 (band 4.1) did not significantly affect the haematological phenotype, despite these two mutations having a PolyPhen score predicting the mutation may be damaging. Exome sequencing allows rapid identification of causative mutations and development of databases of mutations predicted to be disruptive. These tools require further refinement but provide new approaches to the study of genetically defined changes that may impact on blood component storage and transfusion outcome.

Delay in the measurement of eosin-5′-maleimide (EMA) binding does not affect the test result for the diagnosis of hereditary spherocytosis

BACKGROUND

The eosin-5′-maleimide (EMA) binding test is a flow cytometric test widely used to detect hereditary spherocytosis (HS). EMA binds to plasma membrane proteins of red blood cells (RBCs), mainly to band 3 protein. The mean fluorescence of EMA-stained RBCs in HS patients is lower when compared with control RBCs due to the decreased amount of target proteins. EMA dye in aqueous solution is sensitive to light and high temperature. Its fluorescence can decrease when exposed to light or ambient temperatures higher than 4°C. The aim of the study was to evaluate the stability of fluorescence readings of EMA-labeled RBCs over a period of 24 h.

METHODS

The EMA test was performed in peripheral blood from 35 patients with microcytic anemia (five with HS, and 30 without HS). Peripheral blood samples were stained immediately after blood collection and analyzed using a flow cytometer at three time points: 0, after 1 and 24 h of storage at 4°C in the darkness. The results are presented as the percentage of normal control RBCs fluorescence. Flow cytometric studies were performed with Cytomics FC500 (Beckman Coulter, USA).

RESULTS

In HS patients the mean result of the test reached 66.72%±9.26% of normal controls, and in non-HS patients the EMA result was 99.48%±5.03% of normal control cells. The results of patients with HS were 66.72%±9.26%, 66.90%±10.24% and 67.86%±11.31% at 0 h, and after 1 and 24 h of storage, respectively. The results obtained from non-HS patients at time 0, after 1 and 24 h of storage reached 99.48%±5.03%, 99.49%±5.34% and 99.78%±6.13%, respectively. There was no difference between the results from each time point in samples from patients with or without HS.

CONCLUSIONS

Results of the EMA binding test do not depend on storage time of stained samples when stored at 4°C up to 24 h after staining.

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.

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.

Flow cytometric osmotic fragility--an effective screening approach for red cell membranopathies

BACKGROUND

Among the red cell membrane disorders, hereditary spherocytosis (HS) is one of the most common causes of inherited hemolytic anemia. The aim of this study was to compare the flow-cytometric approach for screening of red cell membrane disorders based on osmotic fragility with the eosin-5-maleimide (E5'M) dye test. A group of β-thalassemia heterozygotes were also studied.

METHODS

A red cell suspension was spiked with deionized water during acquisition and the count of residual red cells measured sequentially in real-time using flow cytometry. Fluorescence intensity of red cells stained with eosin-5-maleimide was also measured.

RESULTS

The hereditary spherocytosis (HS) group showed significantly decreased percentage residual red cells (9.31% ± 3.75%) (P = 0.0091) whereas the β-thalassemia group showed a significant increase (93.56% ± 12.98%) (P = 0.0008) compared to the normal control group (46.26% ± 11.33%). The cut off value of the flow cytometric osmotic fragility (FCM OF) test for red cell membrane disorders was 23.59% giving a sensitivity of 100% and specificity of 98%.

CONCLUSIONS

The advantages of the FCM OF test are that it is quantitative, time effective and requires only deionized water for the measurement of osmotic fragility. It could be an effective first line screening approach for red cell membrane disorders in hematology laboratories where a flow cytometer is available.

Clinical utility of flow cytometry in the study of erythropoiesis and nonclonal red cell disorders

Erythropoiesis involves proliferation and differentiation of small population of hematopoietic stem cells resident in the bone marrow into mature red blood cells. The determination of the cellular composition of the blood is a valuable tool in the diagnosis of diseases and monitoring of therapy. Flow cytometric analysis is increasingly being used to characterize the heterogeneous cell populations present in the blood and the hematopoietic cell differentiation and maturation pathways of the bone marrow. Here we discuss the role of flow cytometry in the study of erythropoiesis and nonclonal red blood cell disorders. First, we discuss flow cytometric analysis of reticulocytes. Next, we review salient quantitative methods that can be used for detection of fetal-maternal hemorrhage (FMH). We also discuss flow cytometric analysis of high hemoglobin F (HbF) in Sickle Cell Disease (SCD), hereditary spherocytosis (HS), red cell survival and red cell volume. We conclude by discussing cell cycle of erythroid cells.

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.

Hemolytic anemia and distal renal tubular acidosis in two Indian patients homozygous for SLC4A1/AE1 mutation A858D

Familial distal renal tubular acidosis (dRTA) can be caused by mutations in the Cl2/HCO32 exchanger of the renal Type A intercalated cell, kidney AE1/SLC4A1. dRTA-associated AE1 mutations have been reported in families from North America, Europe, Thailand, Malaysia, Papua-New Guinea, Taiwan, and the Philippines, but not India. The dRTA mutation AE1 A858D has been detected only in the context of compound heterozygosity. We report here two unrelated Indian patients with combined hemolytic anemia and dRTA who share homozygous A858D mutations of the AE1/SLC4A1 gene. The mutation creates a novel restriction site that is validated for diagnostic screening.

Flow cytometric detection of erythrocyte osmotic fragility

BACKGROUND

Hereditary spherocytosis (HS) is the most common cause of inherited chronic hemolysis. The various tests developed for HS screening have many shortcomings. The purpose of this study was to develop a new, simple, reliable test using flow cytometry.

METHODS

In this new test, deionized water, a hemolysis-inducing agent, is spiked to a red cell suspension during acquisition, and the count of red cells is measured sequentially in real-time using flow cytometry. In this study, the optimal parameters for this test were established, and the discriminatory power of the adopted protocol was verified among several groups with various degrees of osmotic fragility (OF).

RESULTS

The established protocol successfully discriminated between blood analyzed immediately and blood stored for 24 h (P < 0.00001). With healthy individuals as a reference, the OF measured by this protocol was significantly decreased in patients with iron deficiency anemia (P = 0.030) and was significantly increased in HS patients (P = 1.1 x 10(-9)). This new test found all 11 HS patients to have increased OF.

CONCLUSIONS

This new test was verified to be simple, quantitative, objective, and cost-effective for the measurement of OF. We suggest this test as another effective approach for HS screening, although its assay performance will require further verification through more clinical trials.

Using the eosin-5-maleimide binding test in the differential diagnosis of hereditary spherocytosis and hereditary pyropoikilocytosis

BACKGROUND

Flow cytometric analysis of eosin-5-maleimide (EMA)-labeled red blood cells (RBCs) has been used as a screening test for the diagnosis of patients with hereditary spherocytosis (HS). We assessed the fluorescence profiles for patients having HS and hereditary pyropoikilocytosis (HPP) together with their red cell indices.

METHODS

Flow cytometry was used to analyze EMA-labeled RBCs. Membrane protein defects and spectrin variants were identified by SDS-polyacrylamide gel electrophoresis.

RESULTS

An overlay of single fluorescence peaks for normal individuals, and those with HS and HPP revealed a graded fluorescence intensity (normal > HS > HPP). The area under each peak defined a specific RBC subpopulation; namely, normal RBCs, spherocytes, and microspherocytes. HS RBCs having a gross reduction in band 3 or spectrin content gave fluorescence readings almost as low as those for HPP. Complex fluorescence profiles were obtained for isolated HS and HPP cases.

CONCLUSIONS

The mean cell volume is a useful discriminator for HS and HPP. We presented evidence that a mixed RBC population could occur in some HS and HPP patients, either in a transient manner or for a long-term period. A differential diagnostic scheme for detecting HPP and HS by flow cytometry is proposed.

Evaluation of eosin-5-maleimide flow cytometric test in diagnosis of hereditary spherocytosis

A flow cytometry-based test using eosin-5-maleimide (EMA) dye was used for diagnosis of hereditary spherocytosis (HS). The mean fluorescence intensiy (MFI) of EMA tagged erythrocytes is lower in HS than that in other hemolytic and nonhemolytic anemias. We enrolled 114 subjects comprising 20 confirmed HS, 20 suspected HS/hemolytic anemia (HA), 20 normal controls, 20 other hemolytic anemias [13 autoimmune hemolytic anemia, three congenital dyserythropoietic anemia (CDA), one pyruvate kinase deficiency, two microangiopathic hemolytic anemia], 18 microcytic anemia and 16 macrocytic anemia cases. All samples were subjected to flow cytometry as per standard protocol. The mean MFI of normal control subjects was 11 861.5 (SD 883.5) and of confirmed HS was 7949.3 (SD 1304.1). Using this test, of 20 patients suspected to be HS/HA but with no confirmatory diagnosis, eight patients were diagnosed as HS. Using logistic regression analysis, the optimum cut-off MFI value between HS and normal controls was 10126. The area under the ROC curve was 0.99. The statistical significance of MFI values was obtained by t-test or Wilcoxon rank sum test as applicable. Compared with normal controls, the MFI values in HS were lower and in megaloblastic anemia were higher which was statistically highly significant (P<0.01), and the MFI values in CDA were lower which was statistically significant (P<0.05). False-positive values were obtained in three cases of AIHA and two cases of CDA. The sensitivity and specificity was 96.4% and 94.2% respectively. The EMA-based flow cytometry test is a highly sensitive and specific method for the diagnosis of HS.