A large cohort of β+-thalassemia in Thailand: Molecular, hematological and diagnostic considerations

Clinical characteristics, laboratory features and genetic profile of hemoglobin E (HBB:c.79 G > A)/β (nucleotide -28 A > G) (HBB:c.-78 A > G) -thalassemia subjects identified from community- and hospital-recruited cohorts

Despite several existing laboratory-based studies of hemoglobin (Hb) E (HBB:c.79 G > A)/ β (nucleotide (NT) -28 A > G) (HBB:c.-78 A > G) -thalassemia, no reports have ever provided clinical severity information as well as dependency of blood transfusion. Previously, a comparative study of community- and hospital-recruited Hb E/β-thalassemia subjects was conducted in the lower northern Thailand between June 2020 and December 2021. A mobile medical team visited each community hospital on-site, collecting clinical severity parameters, and conducting Hb and DNA analyses. The control included Hb E/β-thalassemia patients undergoing transfusions. Subgroup study of adult Hb E/β (NT -28 A > G) -thalassemia subjects was subsequently conducted. Additional pediatric individuals were recruited from prenatal diagnosis databases. Twenty adult and nine pediatric subjects were enrolled; all were classified as having mild disease severity. Twenty-two individuals (75.9 %) were asymptomatic. Six adults (20.7 %) required blood transfusion. The mean Hb level of subjects without transfusion (23 [79.3 %]) was 10.77 ± 1.10 g/dL. Hb analysis revealed a distinct EFA pattern with low Hb F fraction. The positive impact of genetic modifiers could not be statistically demonstrated except rs7482144-XmnI. These findings could provide essential information for parents carrying fetuses with Hb E/β (NT -28 A > G) -thalassemia.

The Importance of Molecular Biological Analysis for the Laboratory Diagnostic of Homozygous Haemoglobin Malay

Haemoglobin (Hb) Malay is variant haemoglobin with a β++ thalassemia phenotype. The prevalence of Hb Malay in the Malaysian population was 5.5%. We describe a 58-year-old male who presented with symptomatic anaemia to the Hospital Universiti Sains Malaysia. Further history revealed that the patient had anaemia since the age of 28, and on regular follow-up at other hospital. Physical examination revealed pallor, jaundice and hepatosplenomegaly. The full blood count and peripheral blood smear showed hypochromic microcytic anaemia with anisopoikilocytosis, and many target cells. High-performance liquid chromatography results showed a β thalassemia trait. However, the diagnosis does not alight with the patient's condition. Bone marrow aspirate was completed and showed reactive changes and erythroid hyperplasia. A molecular test was then performed for β globin gene mutation detection using Multiplex Amplification Refractory Mutation System (M-ARMS) PCR method. This revealed the result as homozygous codon 19 mutation or Hb Malay. Therefore, in this case report we would like to highlight the laboratory approaches, the challenges faced by the usual haematological investigations and the importance role of molecular testing in the diagnosis of severe anaemia.

Molecular understanding of unusual HbE-β+-thalassemia with Hb phenotype similar to HbE heterozygote: simple and rapid differentiation using HbE levels

BACKGROUND

Low HbF expression in HbE-β+-thalassemia may lead to misdiagnosis of HbE heterozygosity. We aimed to characterize the β- and α-globin genes and the modifying factors related to HbF expression in patients with an Hb phenotype similar to that of HbE heterozygotes. Furthermore, screening tools for differentiating HbE-β+-thalassemia from HbE heterozygotes have been investigated.

PARTICIPANTS AND METHODS

A total of 2133 participants with HbE and HbA with varying HbF levels were recruited. Polymerase chain reaction-based DNA analysis and sequencing were performed to characterize β- and α-globin genes. DNA polymorphism at position -158 nt 5' to Gγ-globin was performed by XmnI restriction digestion. Receiver operating characteristic (ROC) curves were constructed using the area under the curve (AUC). Cutoff values of HbA2, HbE, and HbF levels for the differentiation of HbE-β+-thalassemia from HbE heterozygotes were determined.

RESULTS

Five β+-thalassemia mutations trans to βE-gene (β-87(C>A), β-31(A>G), β-28(A>G), β19(A>G), and β126(T>G)) were identified in 79 patients. Among these, 54 presented with low HbF levels, and 25 presented with high HbF levels. ROC curve analysis revealed an excellent AUC of 1.000 (95% confidence interval:1.000-1.000) for HbE levels, and a cut-off point of ≥35.0% had 100.0% sensitivity, specificity, and Youden's index for differentiating HbE-β+-thalassemia from HbE heterozygotes. The proportion of α-thalassemia mutations was 46.3 and 8.0% among HbE-β+-thalassemia patients with low and high HbF levels, respectively. Two rare α-thalassemia mutations (Cap +14(C>G) and initiation codon (ATG>-TG)) of α2-globin genes were identified. The genotype and allele of the polymorphism at -158 nt 5' to Gγ-globin was found to be negatively associated with HbF expression.

CONCLUSIONS

HbE-β+-thalassemia cannot be disregarded until appropriate DNA analysis is performed, and the detection of α-thalassemia mutations should always be performed under these conditions. An HbE level ≥35.0% may indicate screening of samples for DNA analysis for HbE-β+-thalassemia diagnosis.

Molecular basis of a high Hb A2/Hb Fβ-thalassemia trait: a retrospective analysis, genotype-phenotype interaction, diagnostic implication, and identification of a novel interaction with α-globin gene triplication

Background

β ⁰-thalassemia deletion removing 5´β-globin promoter usually presents phenotype with high hemoglobin (Hb) A₂ and Hb F levels. We report the molecular characteristics and phenotype-genotype correlation in a large cohort of the β ⁰-thalassemia with 3.4 kb deletion.

Methods

A total of 148 subjects, including 127 heterozygotes, 20 Hb E-β-thalassemia patients, and a double heterozygote with α-globin gene triplication, were recruited. Hb and DNA analysis were performed to identify thalassemia mutations and four high Hb F single nucleotide polymorphisms (SNPs) including four base pair deletion (-AGCA) at ^A γ-globin promoter, rs5006884 on OR51B6 gene, -158 ^G γ-XmnI, BCL11A binding motifs (TGGTCA) between 3´^A γ-globin gene and 5´δ-globin gene.

Results

It was found that heterozygous β ⁰-thalassemia and Hb E-β ⁰-thalassemia with 3.4 kb deletion had significantly higher Hb, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin and Hb F values as compared with those with other mutations. Co-inheritance of heterozygous β ⁰-thalassemia with 3.4 kb deletion and α-thalassemia was associated with even higher MCV and MCH values. The Hb E-β ⁰-thalassemia patients carried a non-transfusion-dependent thalassemia phenotype with an average Hb of around 10 g/dL without blood transfusion. A hitherto undescribed double heterozygous β ⁰-thalassemia with 3.4 kb deletion and α-globin gene triplication presented as a plain β-thalassemia trait. Most of the subjects had wild-type sequences for the four high Hb F SNPs examined. No significant difference in Hb F was observed between those of subjects with and without these SNPs. Removal of the 5´β-globin promoter may likely be responsible for this unusual phenotype.

Conclusions

The results indicate that β ⁰-thalassemia with 3.4 kb deletion is a mild β-thalassemia allele. This information should be provided at genetic counseling and prenatal thalassemia diagnosis.

Effect of deletions in the α-globin gene on the phenotype severity of β-thalassemia

Thalassemia is the most common inherited hemoglobinopathy worldwide. Variation of clinical symptoms in this hemoglobinopathy entails differences in disease-onset and transfusion requirements. The aim of this study was to investigate the role of α-globin gene deletions in modulating the clinical heterogeneity of β-thalassemia (β-thal) syndromes. A total number 270 β-thal subjects were enrolled. Hematological parameters were recorded. β-Globin mutations were determined by amplified refractory mutation system-polymerase chain reaction (ARMS-PCR), gap-PCR and Sanger sequencing. α-Globin gene deletions were determined by multiplex PCR. Out of 270 β-thal subjects, 19 carried β⁺/β⁺, 74 had β⁰/β⁰ and 177 had the β⁰/β⁺ genotype. When we determined the severity of the different β-thal subjects in coinherited with the α gene deletion, it was revealed that, 84.2% β⁺/β⁺ subjects carried a non severe phenotype and did not have an α gene deletion. Of the β⁰/β⁰ individuals, 95.9% presented a severe phenotype, irrespective of α-globin gene deletions. In cases with the β⁰/β⁺ genotype, 19.2% subjects also carried a deletion on the α gene. Of these, 61.8% presented a non severe phenotype and 38.2% were severely affected. Only in the β⁰/β⁺ category did α gene deletions make a significant contribution (p < 0.001) toward alleviation of clinical severity. Therefore, it can be stated that α-globin gene deletions play a role in ameliorating the phenotype in patients with a β⁺/β⁰ genotype.

Genetic predictions of life expectancy in southern Thai patients with β0‑thalassemia/Hb E

The types of β-thalassemia mutations, α-thalassemia interactions, and Hb F-associated SNPs have been described in association with variable disease phenotypes. This study aimed to determine the updated spectrum of β-thalassemia mutations and evaluate the contribution of primary and secondary genetic modifiers and SNPs to disease severity, age at onset, and predicted life expectancy in southern Thai β-thalassemia patients. A total of 181 β-thalassemia patients were enrolled and 135 β⁰-thalassemia/Hb E patients without α-thalassemia interactions were divided into three categories according to disease severity, age at onset, and predicted life expectancy. A total of 16 β-thalassemia mutations were identified in this study, and the three most common β-thalassemia mutations accounted for 61.4% of all mutations. It was also found that the XmnI polymorphism and rs2071348 were associated with age at onset and the predicted life expectancy. More than 82% of β⁰-thalassemia/Hb E patients with CC genotype (XmnI) were 3 years old or younger at onset. Additionally, >90% of the higher predicted life expectancy in β⁰-thalassemia/Hb E patients had the T allele of XmnI. Therefore, genetic prediction for age at onset and life expectancy is beneficial and practical during prenatal diagnosis or newborn screening for better genetic counseling and optimal management.

Borderline HbA2 levels: Dilemma in diagnosis of beta-thalassemia carriers

There is inconsistency in the exact definition of diagnostic levels of HbA₂ for β thalassemia trait. While many laboratories consider HbA₂ ≥4.0 % diagnostic, still others consider HbA₂ ≥3.3 % or HbA₂ ≥3.5 % as the cut-off for establishing β thalassemia carrier diagnosis. This is because, over the years, studies have described β thalassemia carriers showing HbA₂ levels that lie above the normal range of HbA₂ but below the typical carrier range of β thalassemia. These, "borderline HbA₂ levels", though not detrimental to health, are significant in β thalassemia carrier diagnosis because they can lead to misinterpretation of results. In this review, we have evaluated the prevalence of borderline HbA₂ levels and discussed the causes of borderline HbA₂ values. We have also compiled an extensive catalogue of β globin gene defects associated with borderline HbA₂ levels and have discussed strategies to avoid misdiagnosing borderline HbA₂ β thalassemia carriers. Our analysis of studies that have delineated the cause of borderline HbA₂ levels in different populations shows that 35.4 % [626/1766] of all individuals with borderline HbA₂ levels carry a molecular defect. Among the positive samples, 17 % [299/1766] show β globin gene defects, 7.7 % [137/1766] show α thalassemia defects, 2.7 % [49/1766] show KLF1 gene mutations, 2.3 % [41/1766] show the co-inheritance of β and α thalassemia, 2.0 % [37/1766] show the co-inheritance of β and δ thalassemia and 1.8 % [32/1766] show α globin gene triplication. It appears that a comprehensive molecular work up of the β globin gene is the only definite method to detect borderline HbA₂ β thalassemia carriers, especially in populations with a high prevalence of the disease. The presence of associated genetic or acquired determinants may subsequently be assessed to identify the cause of borderline HbA₂.

Results from 8 years of the proficiency testing program for diagnosis of hemoglobinopathies under the prevention and control program of thalassemia in Thailand

INTRODUCTION

Hemoglobin (Hb) analysis is a key testing for diagnosis of hemoglobinopathies. Accurate analysis, interpretation of results, and genetic risk assessment are important. We report on 8 years of the proficiency testing (PT) program for hemoglobinopathies in Thailand.

METHODS

Laboratory participants were required to test two simulated PT items in each cycle using capillary electrophoresis, one was a husband and another was his pregnant wife. Related hematological parameters were provided. The participants also provide interpretation and evaluate the risk of having three severe thalassemia diseases in an expected fetus. Three cycles were operated per year in accordance with the ISO17043 and ISO13528 guidelines. A total of 84 laboratories throughout Thailand were participated.

RESULTS

A total of 24 PT cycles were performed during 2012-2019. Most participants had Excellent performance for the PT items with normal, β-thalassemia trait, hemoglobin E trait, hemoglobin E trait with α-thalassemia, and Hb H disease. However, when the PT items with homozygous Hb E and Hb E-β-thalassemia were tested, an increase in a Needs improvement performance was noted. From 24 PT cycles, the performance with Excellent, Good, Fair, and Needs improvement was ranging from 10.5%-95.8%, 0%-11.3%, 0%-77.2%, and 2.3%-37.0%, respectively.

CONCLUSION

Most participants have proven their performance to be reliable and demonstrated their abilities to provide interpretation and genetic risk assessment on most of the PT items. For complex thalassemia however, a need to improve the interpretation and risk assessment skills is required which is essential for effective prevention and control of severe thalassemia diseases in Thailand.

Molecular Spectrum of β-Thalassemia Mutations in Central to Eastern Thailand

The aim of this study was to determine the molecular spectrum of β-thalassemia (β-thal) mutations in eastern Thailand. We identified β-thal mutations using allele specific-polymerase chain reaction (ASPCR) and direct DNA sequencing. We found 18 different β-thal mutations in a total of 191 unrelated subjects. Six common β-thal mutations comprised 86.91% of all the mutations, including codons 41/42 (-TTCT) (HBB: c.126_129delCTTT) (35.60%), codon 17 (A>T) (HBB: c.52A>T) (18.85%), -28 (A>G) (HBB: c.-78A>G) (15.71%), IVS-II-654 (C>T) (HBB: c.316-197C>T) (6.28%), IVS-I-1 (G>T) (HBB: c.92+1G>T) (5.76%) and codon 19 (A>G) (HBB:(c.59A>G) (4.71%). In addition, a novel 60 kb deletion in two unrelated cases was characterized and initially suspected to originate from eastern Thailand. Moreover, we demonstrated the molecular spectrum of recent β-thal mutations in Thailand, and data from this study were compared with five reference laboratory centers in Thailand. This study is the first to identify the comprehensive molecular spectrum of β-thal mutations in eastern Thailand, information that may be essential for screening, genetic counseling and prenatal diagnosis (PND) in this region.

Prevalence and distribution of major β-thalassemia mutations and HbE/β-thalassemia variant in Nepalese ethnic groups

BACKGROUND

Beta-thalassemia is a genetic disorder that is inherited in an autosomal recessive pattern. This genetic disease leads to a defective beta-globin hemoglobin chain causing partial or complete beta-globin chain synthesis loss. Beta-thalassemia major patients need a continuous blood transfusion and iron chelation to maintain the normal homeostasis of red blood cells (RBCs) and other systems in the body. Patients also require treatment procedures that are costly and tedious, resulting in a serious health burden for developing nations such as Nepal.

METHODS

A total of 61 individuals clinically diagnosed to have thalassemia were genotyped with multiplex amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). Twenty-one major mutations were investigated using allele-specific primers grouped into six different panels.

RESULTS

The most common mutations found (23%) were IVS 1-5 (G-C) and Cd 26 (G-A) (HbE), followed by 619 deletion, Cd 8/9 (+G), Cd 16 (-C), Cd 41/42 (-TTCT), IVS 1-1 (G-T), Cd 19 (A-G), and Cd 17 (A-T) at 20%, 12%, 8%, 6%, 4%, 3%, and 1%, respectively.

CONCLUSION

The results of this study revealed that Nepal's mutational profile is comparable to that of its neighboring countries, such as India and Myanmar. This study also showed that thalassemia could be detected across 17 Nepal's ethnic groups, especially those whose ancestors originated from India and Central Asia.

Direct Amplification of Whole Blood and Amniotic Fluid Specimens for Prenatal and Postnatal Diagnosis of Hb E-β 0-Thalassemia Diseases

OBJECTIVE

Prenatal and postnatal diagnosis of hemoglobin E-β 0-thalassemia can be made using polymerase chain reaction (PCR) analysis mostly on purified DNA. We have establihed a direct amplification method without DNA extraction on whole blood (WB) and amniotic fluid (AF) specimens to diagnose the disease.

METHODS

Three reactions of WB PCR assays and 7 reactions of AF PCR tests were developed for postnatal and prenatal diagnosis, respectively. Assays were validated against routine tests in a blinded trial.

RESULTS

The results showed 100% concordance with routine DNA PCR assays. Among 309 β-thalassemia carriers, 191 patients (61.8%) carried common β-thalassemia mutations. Among 448 AF specimens, 116 (25.9%) fetuses were found to be affected, 247 (55.1%) fetuses were carriers, and 85 (19%) fetuses were unaffected.

CONCLUSION

We found that WB and AF PCR assays are simple, rapid, and reliable. The developed techniques could be applicable in routine settings.

Lessons learned from a prenatal diagnosis program for thalassemia in Thailand

OBJECTIVE

To assess the outcome of a thalassemia screening program at community hospitals by determining the proportion of at-risk couples able to obtain a prenatal diagnosis (PND) in relation to gestational age (GA).

METHODS

We accessed records documenting prenatal screening for thalassemia in lower northern Thailand between January 2014 and December 2016. The proportion of at-risk pregnancies able to obtain a PND was determined and median GAs at the time of at-risk notification were compared. Reasons for failures to obtain PNDs were analyzed.

RESULTS

Among 4633 screen-positive couples, 259 (5.6%) were identified as at-risk while 23 were excluded due to unconfirmed outcomes. Forty-one declined a PND and were excluded from the final calculations. Of the 195 remaining couples, 140 (71.8%) obtained a PND. Their median GA at the time of at-risk notification was 12.4 (5.6-29.1) weeks, which was earlier than the median GA of 17.7 (6.9-34.6) weeks for couples not undergoing PND (P < .001). Risks for various types of thalassemia and GA were associated with the chances of achieving a PND.

CONCLUSION

In practice, one quarter of couples identified as at-risk were unable to obtain a PND. Time-influencing factors seem to be a major determinant.

Description of a Rare β-Globin Gene Mutation: -86 (C>G) (HBB: c.-136C>G) Observed in a Syrian Family

We present the description of a β-thalassemia (β-thal) -86 (C>G) (HBB: c.-136C>G) mutation in a Syrian family from Damascus, As-Suwayda Province, Syria, who was referred to the laboratory for prenatal diagnosis (PND). The mutation was found in the mother in a homozygous state, while it was in the father and in the amniotic fluid sample in a heterozygous state. This mutation is located at -86 within the proximal CACCC box in the promoter of the β-globin gene and is possibly linked with a phenotype of β⁺-thal. Polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) analysis indicated that the -86 mutation was linked with haplotype I [+ - - - - + +]. We propose that Lebanon may be the origin of this mutation. To the best of our knowledge, this is the first report describing this mutation in As-Suwayda Province. These findings provide novel information on the region-specificity of this mutation in southwestern Syria.

Proficiency testing program for hemoglobin E, A2 and F analysis in Thailand using lyophilized hemoglobin control materials

Background:

There is no external quality assessment (EQA) program for hemoglobin analysis that uses lyophilized hemoglobin control materials with HbA2/E in levels as high as those found in people with the β-thalassemia trait, HbE trait, β-thalassemia/HbE disease or homozygous HbE; these are all found frequently in the southeast Asian population. The aim of this study was to evaluate the efficiency of the control materials used in the established proficiency testing (PT) program at the Associated Medical Sciences-Clinical Service Center (AMC-CSC), Chiang Mai University, Chiang Mai, Thailand.

Methods:

The PT program for Hb analysis and the thalassemia interpretation was established in compliance with ISO/IEC17043:2010. Three cycles per year were performed in 2015 and 2016. In each cycle, three different types of control material were provided to the participants. Each participant analyzed the control materials in the same manner as in their routine practices. Hb analysis results and their thalassemia interpretation codes were entered into the report form and sent back to AMC-CSC.

Results:

The number of participants increased from 63 in 2015 to 76 in 2016. In addition, the number of participants who took part in all three cycles increased from 95.2% (60/63) in 2015 to 100% (76/76) in 2016. All participants reported the correct Hb measurement and type; however, misinterpretations in thalassemia diagnosis were noted.

Conclusions:

The lyophilized hemoglobin control materials prepared at AMC-CSC were used successfully in our PT program. However, the study results indicate the need for further improvement in thalassemia interpretation skills for laboratory staff.

Molecular Understanding of Non-Transfusion-Dependent Thalassemia Associated with Hemoglobin E-β-Thalassemia in Northeast Thailand

Non-transfusion-dependent thalassemia (NTDT) is associated with various forms of thalassemia and genetic modifiers. We report the molecular basis of NTDT in hemoglobin (Hb) E-β-thalassemia disease. This study was done in 73 adult patients encountered at the prenatal diagnosis center of Khon Kaen University, Northeast Thailand. Hematological parameters and Hb patterns were collected, and α- and β-globin gene mutations were determined. Multiple single-nucleotide polymorphisms (SNPs) including the rs7482144/Gγ-XmnI polymorphism, rs2297339, rs2838513, rs4895441, and rs9399137 in the HBS1L-MYB gene, rs4671393 and rs11886868 in the BCL11A gene, and G176AfsX179 in the KLF1 gene were examined. Five β0-thalassemia mutations and a severe β+-thalassemia mutation in trans to the βE gene were identified. No significant difference in hematological parameters was observed among β-thalassemia genotypes. Coinheritance of α-thalassemia was observed in 31 of the 73 subjects (42.5%). Four SNPs including Gγ-XmnI, rs2297339, rs4895441, and rs9399137 of HBS1L-MYB were found to be associated with high Hb F levels in 39 (53.4%) subjects. The molecular basis of NTDT in the remaining 3 (4.1%) cases could not be defined. These results indicate multiple genetic factors in NTDT patients and underline the importance of complete genotyping to provide proper management, make clinical predictions, and improve genetic counseling.