Overview on Hereditary Spherocytosis Diagnosis

INTRODUCTION

Hereditary spherocytosis (HS) is a congenital haemolytic disorder, resulting from plasma membrane protein deficiency of red blood cells (RBCs). Typical pathological signs are anemia, jaundice, and splenomegaly; in newborns, jaundice is the main symptom.

MATERIAL AND METHODS

This study focused on the state of art about the HS diagnosis, from traditional to innovative methods, including diagnostic algorithms that can be applied for pediatric and adult patients, for different laboratory diagnostic levels.

RESULTS

The first erythrocyte parameters used for HS diagnosis were the mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), and red blood cell distribution width (RDW); nowadays new parameters are used in blood cell counter. Advia analyzers (Siemens Medical Solutions) supply the hyper-dense cell percentage (% Hyper), which reflects the red blood cells hyperchromia. Sysmex instruments (i.e. XT-4000i, XE-5000, XN-Series) provide the MicroR, that is the percentage of erythrocytes smaller than 60 fL, Hypo-He, which is the percentage of erythrocytes with a content of hemoglobin less than 17 pg and % Hyper-He, which represents the percentage of RBC with cellular hemoglobin content higher than 49 pg. CELL-DYN Sapphire (Abbott Diagnostics) introduced the HPR parameter (% HPR), which represents the erythrocytes with hemoglobin > 410 g/L. Beckman Coulter instruments supply the mean sphered corpuscular volume (MSCV), which is the average volume of all erythrocytes, including mature erythrocytes and reticulocytes. Other reference tests for screening and diagnosis of HS are the acidified glycerol lysis test (AGLT), the eosin-5-maleimide (EMA) binding test and genetic testing by next-generation sequencing.

CONCLUSIONS

The diagnostic workup of hereditary spherocytosis could be improved thanks to all the available tests, including new molecular tools. However, it requires synergy between clinicians and laboratory staff, evaluating clinical manifestations, all available data related to the disease and the prognosis to fill the diagnostic gaps in the near future.

Complex heterozygous mutations in hereditary spherocytosis: A case report

BACKGROUND

The aim of this study was to investigate the complex heterozygous mutations of ANK1 and SPTA1 in the same individual and improve our understanding of hereditary spherocytosis (HS) in children. We also hope to promote the application of gene detection technology in children with HS, with the goals of identifying more related gene mutations, supporting the acquisition of improved molecular genetic information to further reveal the pathogenesis of HS in children, and providing important guidance for the diagnosis, treatment, and prevention of HS in children.

CASE SUMMARY

A 1-year and 5-month-old patient presented jaundice during the neonatal period, mild anemia 8 months later, splenic enlargement at 1 year and 5 months, and brittle red blood cell permeability. Genetic testing was performed on the patient, their parents, and sister. Swiss Model software was used to predict the protein structure of complex heterozygous mutations in ANK1 and SPTA1. Genetic testing revealed that the patient harbored a new mutation in the ANK1 gene from the father and a mutation in the SPTA1 gene from the mother. Combined with the clinical symptoms of the children, it is suggested that the newly discovered complex heterozygous mutations of ANK1 and SPTA1 may be the cause, providing important guidance for revealing the pathogenesis, diagnosis, treatment, and promotion of gene detection technology in children with HS.

CONCLUSION

This case involves an unreported complex heterozygous mutation of ANK1 and SPTA1, which provides a reference for exploring HS.

Study on Management of Blood Transfusion Therapy in Patients with Hereditary Spherocytosis

Hereditary spherocytosis (HS) is a chronic hemolytic disorder caused by inherited defects in the red blood cell membrane. This study discusses the treatment strategy for the decline in hemoglobin level in three HS probands with moderately severe or severe hemolysis and summarizes the appropriate laboratory tests that help improve clinical management of blood transfusion in HS patients. Three probands who were diagnosed with HS in our hospital and their family members were included in this study. Clinical data of the three families were reviewed to summarize their hematopoietic characteristics. DNA from all family members of the 3 HS probands was amplified by polymerase chain reaction (PCR) and sequenced by the Sanger method to assess genetic relation for HS. Based on the sequencing results, the type of mutated membrane protein in each proband was analyzed using the eosin-5'-maleimide (EMA) binding test and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The hemoglobin level was reduced in all 3 probands after different levels of infection. The fluorescence of EMA-labeled red blood cell (RBC) was decreased. DNA sequencing showed that His54Pro, Leu1858Val, and 6531-12C>T compound heterozygous mutations were present in the SPTA1 gene of patient I-1, Arg344Gln and c.609+86G>A heterozygous mutations were present in the SLC4A1 gene of patient II-1, and Leu2032Pro homozygous mutation was present in the SPTB gene of patient III-1. SDS-PAGE results demonstrated that the concentration of band 3 was reduced in II-1, whereas the levels of the corresponding mutant proteins in the other probands were unchanged. The family members of the respective patients presented mutations in major genes causing HS. The Leu2032Pro mutation identified in patient III-1 is a new missense mutation of the SPTB gene in the Chinese population that has never been reported in literature previously. The presence or absence of acute or chronic infections is a critical deciding factor for the treatment and clinical management of HS patient via blood transfusion. For patients with infections, hemoglobin concentration can be restored once the infection is controlled, thus obviating the need for proper infection control before blood transfusion.

Facilitating EMA binding test performance using fluorescent beads combined with next-generation sequencing

The eosin-5'-maleimide (EMA) binding test is widely used as diagnostic test for hereditary spherocytosis (HS), one of the most common haemolytic disorders in Caucasian populations. We recently described the advantages of replacing the use of healthy control blood samples with fluorescent beads in a modified EMA binding assay. In this study we further explore this novel approach. We performed targeted next-generation sequencing, modified EMA binding test and osmotic gradient ektacytometry on consecutive individuals referred to our laboratory on the suspicion of HS. In total, 33 of 95 carried a (likely) pathogenic variant, and 24 had variants of uncertain significance (VUS). We identified a total 79 different (likely) pathogenic variants and VUS, including 43 novel mutations. Discarding VUS and recessive mutations in STPA1, we used the occurrence of (likely) pathogenic variants to generate a diagnostic threshold for our modified EMA binding test. Twenty-one of 23 individuals with non-SPTA1 (likely) pathogenic variants had EMA ≥ 43.6 AU, which was the optimal threshold in receiver operating characteristic (ROC) analysis. Accuracy was excellent at 93.4% and close to that of osmotic gradient ektacytometry (98.7%). In conclusion, we were able to simplify the EMA-binding test by using rainbow beads as reference and (likely) pathogenic variants to define an accurate cut-off value.

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.

Screening tools for hereditary hemolytic anemia: new concepts and strategies

INTRODUCTION

Hereditary hemolytic anemias are a group of rare and heterogeneous disorders due to abnormalities in structure, metabolism, and transport functions of erythrocytes; they may overlap in clinical and hematological features making differential diagnosis difficult, particularly in mild and atypical forms.

AREAS COVERED

In the present review, the main tools currently adopted in routine hematologic investigation for the diagnosis of hereditary hemolytic anemias are described, together with the new diagnostic approaches that are being to be developed in the next future. Available recommendations in this field together with a systematic review through MEDLINE, EMBASE, and PubMED for publications in English from 2000 to 2020 in regards to diagnostic aspects of hereditary hemolytic anemias have been considered.

EXPERT OPINION

The recent development of specific molecules and treatments for hereditary hemolytic anemias and the increased interest in translational research raised the attention on differential diagnosis and the demand for novel diagnostic assays and devices. Automatic blood cell analyzers, omic-approaches including NGS technologies, and development of new automated tools based on artificial neural networks definitely represent the future strategies in this field.

Improving the EMA Binding Test by Using Commercially Available Fluorescent Beads

Hereditary spherocytosis (HS) is a common anemia caused by germline mutations in red blood cell cytoskeleton proteins. The flow cytometry-based eosin-5′-maleimide (EMA) binding test is most frequently employed for reliable diagnostics. To perform this test, a number of healthy and ideally also age-matched controls are required, which can be challenging and complicates interlaboratory comparisons. To overcome this limitation, we modified the EMA binding test by replacing healthy controls with commercially available fluorescent beads. Blood samples from 289 individuals with suspected HS were analyzed using the EMA binding test with fluorescent beads and benchmarked against regular EMA binding test using two control samples. Using osmotic gradient ektacytometry as validation, 112 individuals (38.8%) were diagnosed with HS. Performance of the modified EMA binding test was not compromised (accuracy 90.3%) compared to EMA binding test using matched controls (accuracy 88.6%). Based on these findings, we conclude that the modified EMA binding test with fluorescent beads is an attractive alternative, especially in laboratories without easy access to matched controls. Furthermore, as fluorescent beads are stable and easily commutable, they could facilitate both interlaboratory comparisons and quality assessment programs.

Next-Generation Sequencing-Based Diagnosis of Unexplained Inherited Hemolytic Anemias Reveals Wide Genetic and Phenotypic Heterogeneity

Determination of the cause of inherited hemolysis is based on clinical and stepwise conventional laboratory tests. Patients with obscure etiology require genetic diagnosis, which is time-consuming, expensive, and laborious, mainly because of numerous causal genes. This study enrolled 43 patients with clinical and laboratory evidence of unexplained hemolytic anemia. Initially, 13 patients were tested using a commercial (TruSight One) panel, and remaining cases underwent targeted sequencing using a customized 55-gene panel. Pyruvate kinase deficiency was found in eight, glucose-6-phosphate dehydrogenase (G6PD) deficiency in three (G6PD Guadalajara in two and p.Tyr227Ser: novel, named as G6PD Chandigarh), and glucose-6-phosphate isomerase (GPI) deficiency in two (GPI:p.Arg347His and p.Phe304Leu: novel, named as GPI Chandigarh). Three patients had Mediterranean stomatocytosis/macrothrombocytopenia, and two had overhydrated stomatocytosis. Xerocytosis was found in three patients, whereas six had potentially pathogenic variants in membrane protein-coding genes. Overall, 63% cases received a definite diagnosis. Timely determination of etiology was helpful in diagnosis, genetic counseling, and offering a prenatal diagnosis. Therapeutic implications include performing or avoiding splenectomy that may ameliorate the anemia in many but also predispose to thrombosis in other groups of patients. This first study on the genetic spectrum of unexplained hemolytic anemia from the Indian subcontinent also represents, currently, one of the largest cohort worldwide of such patients.

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.

Deciphering molecular heterogeneity of Indian families with hereditary spherocytosis using targeted next-generation sequencing: First South Asian study

Defects in various erythrocyte membrane proteins genes (ankyrin, band-3, β- and α-spectrin and protein 4·2) can cause hereditary spherocytosis (HS). This molecular heterogeneity of HS, together with co-inherited genetic modifiers, results in marked phenotypic variability among patients. We studied the molecular spectrum and genotype-phenotype correlations in 73 families (with 113 patients) with HS. Deleterious variants including nonsense (42%), deletions (18%), splice site (20%), missense (10%) and duplication/insertion (10%) were found in 47 patients. The variants detected included sporadic and dominantly-inherited defects in ANK1 (53·2%), SPTB (36·2%) and SLC4A1 (4·2%). Compound heterozygous variants in SPTA1 (6·4%) showed autosomal recessive inheritance. Alpha-spectrin variants were associated with severe anaemia and splenectomy alleviated symptoms. Co-inherited glucose-6-phosphate dehydrogenase (G6PD) deficiency was found in 15%. G6PD variants (n = 5) led to greater transfusion requirements (1-8 times) in males with HS. Homozygosity (41%) for the promoter variant of UGT1A1 (Gilbert syndrome) led to a significantly higher mean bilirubin level (126·54 µmol/l) with a higher frequency of cholelithiasis (30%) (P < 0·001). This first-ever south Asian study on the molecular spectrum of HS found ANK1 and SPTB genes variants to be the commonest with inheritance being sporadic/dominant. Next-generation sequencing provided a relatively sensitive and rapid tool for molecular diagnosis with a diagnostic yield of 64·4%.

Old and new insights into the diagnosis of hereditary spherocytosis

Hereditary spherocytosis (HS) belongs to the group of congenital hemolytic anemias resulting from plasma membrane protein deficiency. When diagnosed too late, HS bares the risk of long-term complications including gall stones and severe anemia. Here, there are discussed advances in HS screening and diagnostics, with a particular focus on methodologies, most of which are available in clinical laboratories worldwide.

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.

Optimal Reference Gene Selection for Expression Studies in Human Reticulocytes

Reference genes are indispensable for normalizing mRNA levels across samples in real-time quantitative PCR. Their expression levels vary under different experimental conditions and because of several inherent characteristics. Appropriate reference gene selection is thus critical for gene-expression studies. This study aimed at selecting optimal reference genes for gene-expression analysis of reticulocytes and at validating them in hereditary spherocytosis (HS) and β-thalassemia intermedia (βTI) patients. Seven reference genes (PGK1, MPP1, HPRT1, ACTB, GAPDH, RN18S1, and SDHA) were selected because of published reports. Real-time quantitative PCR was performed on reticulocytes in 20 healthy volunteers, 15 HS patients, and 10 βTI patients. Threshold cycle values were compared with fold-change method and RefFinder software. The stable reference genes recommended by RefFinder were validated with SLC4A1 and flow cytometric eosin-5'-maleimide binding assay values in HS patients and HBG2 and high performance liquid chromatography-derived percentage of hemoglobin F in βTI. Comprehensive ranking predicted MPP1 and GAPDH as optimal reference genes for reticulocytes that were not affected in HS and βTI. This was further confirmed on validation with eosin-5'-maleimide results and percentage of hemoglobin F in HS and βTI patients, respectively. Hence, MPP1 and GAPDH are good reference genes for reticulocyte expression studies compared with ACTB and RN18S1, the two most commonly used reference genes.

Targeted next-generation sequencing identifies a novel nonsense mutation in SPTB for hereditary spherocytosis: A case report of a Korean family

RATIONALE

Hereditary spherocytosis (HS) is an inherited disorder characterized by the presence of spherical-shaped red blood cells (RBCs) on the peripheral blood (PB) smear. To date, a number of mutations in 5 genes have been identified and the mutations in SPTB gene account for about 20% patients.

PATIENT CONCERNS

A 65-year-old female had been diagnosed as hemolytic anemia 30 years ago, based on a history of persistent anemia and hyperbilirubinemia for several years. She received RBC transfusion several times and a cholecystectomy roughly 20 years ago before. Round, densely staining spherical-shaped erythrocytes (spherocytes) were frequently found on the PB smear. Numerous spherocytes were frequently found in the PB smears of symptomatic family members, her 3rd son and his 2 grandchildren.

DIAGNOSIS

One heterozygous mutation of SPTB was identified by targeted next-generation sequencing (NGS). The nonsense mutation, c.1956G>A (p.Trp652*), in exon 13 was confirmed by Sanger sequencing and thus the proband was diagnosed with HS.

INTERVENTIONS

The proband underwent a splenectomy due to transfusion-refractory anemia and splenomegaly.

OUTCOMES

After the splenectomy, her hemoglobin level improved to normal range (14.1 g/dL) and her bilirubin levels decreased dramatically (total bilirubin 1.9 mg/dL; direct bilirubin 0.6 mg/dL).

LESSONS

We suggest that NGS of causative genes could be a useful diagnostic tool for the genetically heterogeneous RBC membrane disorders, especially in cases with a mild or atypical clinical manifestation.

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.