A large cohort of deletional high hemoglobin F determinants in Thailand: A molecular revisited and identification of a novel mutation

BACKGROUND AND AIMS

High hemoglobin F determinants can be classified into hereditary persistence of fetal hemoglobin (HPFH) and δβ-thalassemia with different phenotype. We report the molecular basis and hematological features in a large cohort of deletional high Hb F determinants in Thailand.

MATERIALS AND METHODS

Subjects (n = 28,177) encountered during 2015-2022 were reviewed, and those with phenotypically suspected of having high Hb F determinants were selected. Combined PCR, multiplex ligation-dependent probe amplification, next-generation sequencing, and DNA sequencing were used to identify the mutations.

RESULTS

Among 28,177 subjects investigated, 300 (1.06 %) were found to carry deletional high Hb F determinants in a total of 302 alleles, including heterozygote, compound heterozygote with β-hemoglobinopathies, and homozygote. DNA analysis identified eight different DNA deletions, including δβ0-thalassemia (12.6 kb deletion) (73.8 %), HPFH-6 (14.9 %), Indian deletion-inversion Aγδβ0-thalassemia (3.6 %), Thai deletion-inversion-insertion Aγδβ0-thalassemia (3.0 %), SEA-HPFH (3.0 %), Chinese Aγδβ0-thalassemia (1.0 %), Thai δβ0-thalassemia (11.3 kb deletion) (0.3 %), and a novel δβ0-thalassemia (137.1 kb deletion) (0.3 %). In addition, three novel genetic interactions, including Chinese Aγδβ0-thalassemia/Hb E, δβ0-thalassemia/Indian deletion-inversion Aγδβ0-thalassemia, and homozygous δβ0-thalassemia were found. Hematological features and Hb analysis results of 20 different genotypes were recorded. Multiplex gap-PCR assays for detection of these genetic determinants were described.

CONCLUSIONS

Deletional high Hb F determinants are common and heterogeneous in Thailand. Data on the prevalence, molecular spectrum, phenotypic expression, and complex interactions of these genetic determinants should prove useful in the study and a prevention and control program of hemoglobinopathies in the region.

Molecular and haematological characterisation of haemolytic anaemia associated with biallelic KLF1 mutations: a case series

AIMS

Krüppel-like factor 1 (KLF1) is an erythroid-specific transcription factor playing an important role in erythropoiesis and haemoglobin (Hb) switching. Biallelic KLF1 mutations can cause haemolytic anaemia with thalassaemia-like syndromes but are rarely reported. We explore the KLF1 mutations in Thai subjects with unexplainable haemolytic anaemia.

METHODS

The study was done on 57 subjects presented with haemolytic anaemia and elevated Hb F without β-thalassaemia diseases. Hb analysis was performed using capillary electrophoresis. Analyses of α-thalassaemia, β-thalassaemia and KLF1 genes were performed using PCR-based methods and DNA sequencing.

RESULTS

Thirteen subjects with compound heterozygous for a known and five new genetic KLF1 interactions were identified, including KLF1:c.519_525dupCGGCGCC/c.892G>C with class 3/2 (n=8), and each subject with new genetic interaction, including KLF1:c.-154C>T;643C>T/c.983G>A with class 3/2, KLF1:c.-154C>T;643C>T/c.809C>G with class 3/2, KLF1:c892G>C/c.983G>A with class 2/2, KLF1:c.892G>C/c.1001C>G with class 2/2 and KLF1:c.1001C>G/c.1003G>A with class 2/2. Most of them had anaemia with Hb levels ranging from 45 to 110 g/L, hypochromic microcytosis, aniso-poikilocytosis, increased Hb F levels (17.9%-47.4%), small amounts of Hb Bart's, regular blood transfusion, hyperbilirubinaemia, increased serum ferritin and nucleated red blood cell.

CONCLUSIONS

Biallelic KLF1 mutations associated with anaemia may not be uncommon in Thailand. Characteristics of haemolytic anaemia, abnormal red cell morphology with nucleated red blood cells and elevated Hb F, and presenting small amounts of Hb Bart's without thalassaemia diseases are useful markers to further investigation of the KLF1 gene.

Molecular basis of non-deletional HPFH in Thailand and identification of two novel mutations at the binding sites of CCAAT and GATA-1 transcription factors

High Hb F determinants are genetic defects associated with increased expression of hemoglobin F in adult life, classified as deletional and non-deletional forms. We report the first description of non-deletional hereditary persistence of fetal hemoglobin (HFPH) in Thailand. Study was done on 388 subjects suspected of non-deletional HPFH with elevated Hb F expression. Mutations in the Gγ- and Aγ-globin genes were examined by DNA analysis and rapid diagnosis of HPFH mutations were developed by PCR-based methods. Twenty subjects with five different mutations were identified including three known mutations, - 202 Aγ (C>T) (n = 3), - 196 Aγ (C>T) (n = 3), and - 158 Aγ (C>T) (n = 12), and two novel mutations, - 117 Aγ (G>C) (n = 1) and - 530 Gγ (A>G) (n = 1). Interaction of the - 117 Aγ (G>C) and Hb E (HBB:c.79G>A) resulted in elevation of Hb F to the level of 13.5%. Two plain heterozygous subjects with - 530 Gγ (A>G) had marginally elevated Hb F with 1.9% and 3.0%, whereas the proband with homozygous - 530 Gγ (A>G) had elevated Hb F of 11.5%. Functional prediction indicated that the - 117 Aγ (G>C) and - 530 Gγ (A>G) mutations dramatically alter the binding of transcription factors to respective γ-globin gene promotors, especially the CCAAT and GATA-1 transcription factors. Diverse heterogeneity of non-deletional HFPH with both known and new mutations, and complex interactions of them with other forms of thalassemia are encountered in Thai population.

Hemoglobin EE disease in young Laotian children: Hematologic features and the contributions of genetic variations to Hb F expression

BACKGROUND

The wide variation in hemoglobin (Hb) F levels has been observed in patients with Hb EE disease. This study aimed to describe hematologic features and determine the effect of genetic variants on Hb F expression in young children with Hb EE disease.

METHODS

Hematologic features and Hb profiles of Laotian children aged 6-23 months, who originally enrolled in the Lao-Zinc study, were retrospectively reviewed. Only children with Hb EE disease, as indicated by DNA analysis, were included in this current analysis. Genetic variants, including the ^G γ-XmnI polymorphism (C>T) of the HBG2 gene, the HBS1L-MYB intergenic region on chromosome 6, and the BCL11A on chromosome 2 as well as the mutations occurring on the Krüppel-like factor 1 (KLF1) gene, were examined.

RESULTS

In total, 205 children were diagnosed as having Hb EE disease with Hb F ranged from 1.2 to 43.7%. Most of the children had mild to moderate anemia with a remarkable microcytosis. Analysis of the genetic variants revealed an extremely high frequency of the ^G γ-XmnI (93.7%). Applying multiple regression analysis adjusted for age, sex, and α-thal gene, a positive relation was observed for the rs4671393 (coefficient = 3.87, p = .005) and the rs2297339 (coefficient = 2.48, p = .046), but not the ^G γ-XmnI. A statistically non-significant relation was noted for the rs9399137 and the -154 (C>T) KLF1 mutation.

CONCLUSION

Our findings provide insight into complex situation of Hb F variability in young children with Hb EE disease; and this can guide to appropriate care and counseling to affected families.

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.

Frequency of unnecessary prenatal diagnosis of hemoglobinopathies: A large retrospective analysis and implication to improvement of the control program

OBJECTIVE

To determine the frequency and etiology of unnecessary prenatal diagnosis for hemoglobinopathies during 12 years of services at a single university center in Thailand.

METHODS

We conducted a retrospective cohort analysis of prenatal diagnosis during 2009-2021. A total of 4,932 couples at risk and 4,946 fetal specimens, including fetal blood (5.6%), amniotic fluid (92.3%), and chorionic villus samples (2.2%) were analyzed. Identification of mutations causing hemoglobinopathies was carried out by PCR-based methods. Maternal contamination was monitored by analysis of the D1S80 VNTR locus.

RESULTS

Among 4,946 fetal specimens, 12 were excluded because of poor PCR amplification, maternal contamination, non-paternity, and inconsistency of the results of the fetuses and parents. Breakdown of 4,934 fetuses revealed 3,880 (78.6%) at risk for the three severe thalassemia diseases, including β-thalassemia major, Hb E-β-thalassemia, and homozygous α0-thalassemia, 58 (1.2%) at risk for other α-thalassemia diseases, 168 (3.4%) at risk for β+-thalassemia, 109 (2.2%) at risk for high Hb F determinants, 16 (0.3%) at risk for abnormal Hbs, and 294 (6.0%) with no risk of having severe hemoglobinopathies. The parents of 409 (8.3%) fetuses had inadequate data for fetal risk assessment. Overall, we encountered unnecessary prenatal diagnostic requests for 645 (13.1%) fetuses.

CONCLUSIONS

The frequency of unnecessary prenatal diagnosis was high. This could lead to unnecessary risk of complications associated with fetal specimen collection, psychological impacts to the pregnant women and their families, as well as laboratory expenses and workload.

Phosphatidylserine-exposed red blood cells and ineffective erythropoiesis biomarkers in patients with thalassemia

OBJECTIVE

The degree of ineffective erythropoiesis is known to be associated with clinical severity among individuals with thalassemia. The association of ineffective erythropoiesis biomarker levels with different thalassemia genotypes, however, remains limited. The aim of this study was to explore the level of phosphatidylserine-exposed red blood cells (PS-exposed RBCs) and ineffective erythropoiesis biomarkers (growth-differentiation factor-15 and soluble transferrin receptors) in patients with different genotypes.

METHODS

A cross-sectional study was conducted on 139 patients of age 18 years and above with different genotypes at Srinagarind Hospital, Khon Kaen University, Thailand. The levels of PS-exposed RBCs were determined using flow cytometry. Measurements of growth-differentiation factor-15 (GDF-15) and soluble transferrin receptors (sTfR) were evaluated by the ELISA method.

RESULTS

The PS-exposed RBCs levels were found to be significantly higher in splenectomized beta-thalassemia patients. Patients with beta-thalassemia had the highest GDF-15 levels, followed by patients with non-deletional alpha-thalassemia. Patients with non-deletional alpha-thalassemia showed elevated hemoglobin levels and reduced GDF-15 levels after splenectomy. Patients with beta-thalassemia and non-deletional alpha-thalassemia had the highest levels of PS-exposed RBCs and ineffective erythropoiesis biomarkers, which correlated with the clinical severity of thalassemia.

CONCLUSIONS

The levels of ineffective erythropoiesis biomarkers were different across thalassemia genotypes. Splenectomy may improve clinical symptoms of patients with non-deletional alpha thalassemia but not of patients with beta-thalassemia. These findings demonstrate differences in the degree of ineffective erythropoiesis in thalassemia, which emphasizes the need for different treatment approaches among patients with different thalassemia genotypes.

α0-thalassemia in affected fetuses with hemoglobin E-β0-thalassemia disease in a high-risk population in Thailand

OBJECTIVES

A co-inheritance of α⁰-thalassemia can ameliorate the clinical severity of the hemoglobin (Hb) E-β-thalassemia disease. This information should be provided at prenatal diagnosis. Identification of α⁰-thalassemia in an affected fetus is therefore valuable. We have explored this genetic interaction in a large cohort of affected fetuses with hemoglobin (Hb) E-β-thalassemia in northeast Thailand.

METHODS

A study was done retrospectively on 1,592 couples at risk of having fetuses with Hb E-β⁰-thalassemia, encountered from January 2011 to December 2019. A total of 415 left-over DNA specimens of the affected fetuses with Hb E-β⁰-thalassemia disease were further investigated. Examination of α⁰-thalassemia was done using gap-PCR or a multiplex PCR assay for simultaneous detection of Hb E and α⁰-thalassemia mutations.

RESULTS

Of the 415 affected fetuses, the two most common β⁰-thalassemia genes found were the codons 41/42 (-TTCT) (199/415; 48.0%) and codon 17 (A-T) (115/415; 27.7%). α⁰-thalassemia was found unexpectedly in 21 (5.1%) fetuses. Hematologic phenotypes of the parents indicated that it was impossible to differentiate a pure β⁰-thalassemia carrier from a double β⁰-thalassemia/α⁰-thalassemia heterozygote unless DNA analysis is performed. In contrast, a reduced level of Hb E in the Hb E carrier (<25%) is a valuable marker for predicting double heterozygosity for Hb E/α⁰-thalassemia. This could be further confirmed using a multiplex PCR assay.

CONCLUSIONS

There is a high prevalence of co-inheritance of α⁰-thalassemia in fetuses with Hb E-β⁰-thalassemia disease. In a high-risk population such as Thailand, we recommend screening for α⁰-thalassemia in all affected fetuses with Hb E-β⁰-thalassemia disease and providing complete genetic information to the parents to make appropriate decisions at prenatal diagnosis and genetic counseling.

Diagnostic value of fetal hemoglobin Bart's for evaluation of fetal α-thalassemia syndromes: application to prenatal characterization of fetal anemia caused by undiagnosed α-hemoglobinopathy

Background

To evaluate whether the quantification of fetal hemoglobin (Hb) Bart’s is useful for differentiation of α-thalassemia syndromes in the fetus and to characterize the fetal anemia associated with fetal α-hemoglobinopathy.

Methods

A total of 332 fetal blood specimens collected by cordocentesis were analyzed using capillary electrophoresis and the amount of Hb Bart’s was recorded. The result was evaluated against thalassemia genotypes determined based on Hb and DNA analyses. Prenatal Hb and DNA characterization of the fetal anemia observed in two families was done.

Results

Among 332 fetuses investigated, Hb and DNA analyses identified 152 fetuses with normal genotypes. The remaining 180 fetuses carried α-thalassemia with several genotypes. Variable amounts of Hb Bart’s were identified in all fetuses with α-thalassemia, which could be used for simple differentiation of fetal α-thalassemia genotypes. These included α⁺- and α⁰-thalassemia traits, homozygous α⁺-thalassemia and Hb Constant Spring (CS), Hb H disease, Hb H-CS and Hb H-Quong Sze diseases, homozygous α⁰-thalassemia causing the Hb Bart’s hydrops fetalis and a remain uncharacterized α-thalassemia defect. The previously undescribed interactions of Hb Queens Park and Hb Amsterdam A1 with Hb E were detected in two fetuses with Hb Bart’s of 0.5%. The Hb Queens Park-AEBart’s disease was also noted in one pregnant woman. Prenatal analysis of the fetuses with severe fetal anemia and cardiomegaly with Hb Bart’s of 9.0% and 13.6% revealed unexpectedly the homozygous Hb CS and a compound heterozygosity of Hb CS/Hb Pakse’ with Hb E heterozygote, respectively.

Conclusions

The usefulness of detecting and differentiation of fetal α-thalassemia syndromes by quantifying of Hb Bart’s was demonstrated. Apart from the fatal condition of Hb Bart’s hydrops fetalis associated with homozygous α⁰-thalassemia, homozygous Hb CS and a compound Hb CS/Hb Pakse’ could result in severe fetal anemia and fetal complications, prenatal diagnosis is highly recommended. The simple Hb Bart’s quantification of fetal blood should prove helpful in this matter.

Thalassemia and erythroid transcription factor KLF1 mutations associated with borderline hemoglobin A2 in the Thai population

INTRODUCTION

Elevated hemoglobin (Hb) A₂ is an important diagnostic marker for β-thalassemia carriers. However, diagnosis of cases with borderline Hb A₂ may be problematic. We described the molecular characteristics found in a large cohort of Thai subjects with borderline Hb A₂.

MATERIAL AND METHODS

Examination was done on 21,657 Thai subjects investigated for thalassemia at Khon Kaen University, Thailand. A total of 202 subjects with borderline Hb A₂ (3.5-4.0%) were selectively recruited and hematological parameters were recorded. DNA variants in α-, β-, δ-globin, and Krüppel-like factor 1 (KLF1) genes were examined using PCR.

RESULTS

Among 202 subjects, DNA analysis identified carriers of α⁺-thalassemia (n = 48; 23.8%), β-thalassemia (n = 22; 10.9%) and KLF1 mutations (n = 48; 23.8%). No molecular defect was observed in the remaining 84 (41.5%) subjects. Interaction of KLF1 and α-thalassemia was observed in 10 cases. Of the 22 β-thalassemia carriers, five β⁺-thalassemia mutations were identified with lower MCV and higher Hb A₂. Seven KLF1 mutations were detected in 10 genotypes in subjects with higher MCV and Hb F. No β⁰-thalassemia, α-globin gene triplication or δ-globin gene mutation was detected.

CONCLUSIONS

A large proportion of subjects with borderline Hb A₂ are not β-thalassemia carriers and for those with β-thalassemia, only mild β⁺-thalassemia mutations were detected. Evaluation of the patients using Hb A₂, Hb F and MCV values will help in selecting cases for further molecular analysis. The results should explain the unusual phenotype of the cases and facilitate a thalassemia screening program in the region.

Generation of a single-tube quality control material for hemoglobin and DNA analyses of hemoglobinopathies

INTRODUCTION

Hemoglobinopathies are major public health problems worldwide. Accurate laboratory diagnosis of the carrier is essential, which includes initial screening, Hb analysis, and DNA analysis. For the first time, we have developed a single-tube quality control (QC) sample for these laboratory tests.

METHODS

The QC sample was made from a lyophilized mixture of the stabilized hemolysate with carbon monoxide saturation and the white blood cells of known thalassemia mutations. Homogeneity and stability were examined by Hb and DNA analyses on day 0 and every month for 12 months, at room temperature, 4°C, and -20°C. A preliminary proficiency testing (PT) program for hemoglobinopathies using this single QC material was developed.

RESULTS

Hemoglobin (Hb) and DNA analyses of a single-tube QC sample demonstrated satisfactory results of Hb analysis for at least five months and DNA analysis for at least one year of storage at -20°C. The results obtained from a preliminary PT program on five expert laboratories confirmed that a single tube QC sample prepared could be used as a PT item with various Hb and DNA analyses methods.

CONCLUSION

A single lyophilized control sample has been generated for use in hemoglobinopathies' internal and external quality control program. Unlike other available control materials, which are used for individual testing, a single-tube QC sample generated can be used to control the pre-analytical and analytical processes of both Hb and DNA analyses and is suitable for use in the PT program of hemoglobinopathies.

Genetic and non-genetic factors affecting hemoglobin A2 expression in a large cohort of Thai individuals: implication for population screening for thalassemia

OBJECTIVE

Increased hemoglobin (Hb) A₂ level is an important diagnostic marker for β-thalassemia carrier screening. The level of Hb A₂ is also useful for differentiating several thalassemia syndromes. We have examined data bases for reduced Hb A₂ expression in a large cohort of Thai subjects.

METHODS

A study was done on 1,498 subjects with non-thalassemia and various types of thalassemia and Hb variants to determine the effect of thalassemia genotypes and on 103 women of reproductive age to determine the effect of iron deficiency. Hb analysis was done using capillary electrophoresis, and thalassemia genotypes were defined by DNA analysis. Serum ferritin was measured using chemiluminescent microparticle immunoassay.

RESULTS

Subjects were divided into 35 groups based on iron status, Hb, and DNA analysis. Decreased Hb A₂ level was observed in those with Hb Q-Thailand, δ-hemoglobinopathies, δβ⁰-thalassemia, Hb Lepore, iron deficiency, α-thalassemia, and especially Hb Constant Spring (Hb CS). While β-thalassemia carriers with Hb H disease still had elevated Hb A₂ levels, most of the β-thalassemia carriers with Hb H-CS disease had Hb A₂ less than 3.5% as a diagnostic cut-off. The lowest Hb A₂ level was observed in those with Hb H-CS disease.

CONCLUSION

Iron deficiency, Hb CS trait, homozygous Hb CS, and Hb H disease may reduce Hb A₂ level, leading possibly to misdiagnosis of β-thalassemia, especially in carriers with borderline Hb A₂. Hb CS showed the strongest effect on Hb A₂ expression. Understanding the basis for reduced Hb A₂ expression may help reduce the diagnostic pitfalls of β-thalassemia in the region.

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.

A New Indicator Derived From Reticulocyte Hemoglobin Content for Screening Iron Deficiency in an Area Prevalent for Thalassemia

OBJECTIVE

To establish a new indicator derived from reticulocyte hemoglobin (Ret-He) content and red blood cell (RBC) indices for screening for iron deficiency anemia (IDA) in an area in whch thalassemia is prevalent.

METHODS

Blood specimens from 304 women aged between 18 and 30 years residing in northeast Thailand were collected and measured for RBC and reticulocyte parameters. Iron deficiency was diagnosed when a participant had a serum ferritin level of less than 15 ng per mL. Thalassemia genotypes were defined by hemoglobin (Hb) and DNA analyses.

RESULTS

Of the total participants, 25% had iron deficiency (ID) and 50% carried the thalassemia gene. Various mathematical formulas were established and analyzed using the receiver operating characteristic (ROC) curve. The formula derived from Ret-He: (Ret-He/RDW-SD) × 10, was the best predictor for identifying ID among participants (area under the curve [AUC] = 0.812). Further testing of this indicator among individuals with positive thalassemia-screening results revealed stronger performance with an AUC of 0.874.

CONCLUSIONS

The findings indicate that the formula derived from Ret-He might be applicable for screening ID in areas in which thalassemia is prevalent.

δ-Hemoglobinopathies in Thailand: screening, molecular basis, genotype-phenotype interaction, and implication for prevention and control of thalassemia

The δ-globin gene defects are clinically silent but interaction with β-thalassemia can lead to a misdiagnosis of β-thalassemia carrier. We report an extensive molecular characterization of δ-hemoglobinopathies in Thailand. Study was done on 32,108 subjects, encountered at the thalassemia screening. Six different approaches based on the reduced Hb A₂ or appearance of Hb A₂-derivative were established for selective recruitment of subjects. Among 32,108 subjects, a total of 296 subjects were suspected of having δ-globin gene defects. Of these 296 subjects, Hb and DNA analyses identified δ-hemoglobinopathies with 10 different mutations in 34 (0.11%) of them. These included a novel mutation, [δ^{CD30(AGG>GGG)} (n = 1)], 5 previously undescribed in Thailand, [δ^-44(G>A) (n = 7), Hb A₂-Troodos (n = 5), δ^{IVSII-897(A>C)} (n = 4), δ^-68(C>T) (n = 2), and Hb A₂-Indonesia (n = 1)], and 4 mutations previously found in Thailand, [Hb A₂-Melbourne (n = 9), δ^-77(T>C) (n = 3), Hb A₂' (n = 1), and Hb A₂-Kiriwong (n = 1)]. Genetic heterogeneities seen included interactions of δ-globin gene defects with heterozygous Hb E, β-thalassemia, α-thalassemia, and in cis locations of the Hb A₂-Troodos and Hb E mutations found for the first time. Rapid identification methods of these δ-globin gene mutations were developed. The results should prove useful to a prevention and control program of hemoglobinopathies in the region.

Southeast Asian Ovalocytosis and Hemoglobinopathies in Newborns: Prevalence, Molecular, and Hematologic Analyses

OBJECTIVES

Southeast Asian ovalocytosis (SAO) is an inherited red blood cell (RBC) membrane disorder, whereas hemoglobinopathies are inherited globin gene disorders. In an area where both diseases are prevalent, the interaction between them resulting in variable hematologic parameters can be encountered. However, little is known about the genetic interaction of SAO and thalassemia. We investigated the prevalence of SAO and hemoglobinopathy genotypes among newborns in southern Thailand.

PATIENTS AND METHODS

This study was carried out on 297 newborns recruited consecutively at Naradhiwas Rajanagarindra Hospital in the south of Thailand. The SAO was identified on blood smear examination and polymerase chain reaction analysis. Thalassemia genotypes were defined. Hematologic parameters and hemoglobin (Hb) profiles were recorded and analyzed.

RESULTS

Among 297 newborns, 15 (5.1%) carried SAO, whereas 70 (23.6%) had thalassemia with 15 different thalassemia genotypes. Abnormal Hb including Hb C, Hb Q-Thailand, and Hb D-Punjab were observed in 5 newborns. It was found in the nonthalassemic newborns that RBC count, Hb, and hematocrit of the nonthalassemic newborns with SAO were significantly lower than those without SAO. The same finding was also observed in the thalassemic newborns; RBC count, Hb, and hematocrit of the thalassemic newborns with SAO were significantly lower than those without SAO. However, the mean corpuscular volume, mean corpuscular Hb, and RBC distribution width of the SAO-newborns were significantly higher.

CONCLUSIONS

Both SAO and hemoglobinopathy genotypes are common in southern Thailand. One should take this into consideration when evaluating neonatal anemia and other hematologic abnormalities. Identification of both genetic defects and long-term monitoring on the clinical outcome of this genetic interaction should be essential to understand the pathogenesis of these common genetic disorders in the region.

β-Hemoglobinopathies in the Lao People's Democratic Republic: Molecular diagnostics and implication for a prevention and control program

INTRODUCTION

A high frequency of β-thalassemia in Lao People's Democratic Republic necessitates the importance of complete molecular data before a prevention and control program could be established. Limited data are available for Lao PDR. We have now reported an extended information on the molecular basis of β-hemoglobinopathies in this population.

METHODS

The study was done on 519 unrelated Laos subjects requested for thalassemia investigation. Hematological data were recorded. Hb profiles were obtained using a capillary electrophoresis system. α-And β-globin genotyping was performed using PCR and related techniques.

RESULTS

Among the 519 subjects, 287 (55.3%) were found to carry β-hemoglobinopathies based on Hb and DNA analyses. These included Hb E carriers (n = 135), homozygous Hb E (n = 47), β-thalassemia carriers (n = 70), Hb E-β-thalassemia (n = 25), homozygous β-thalassemia (n = 4), heterozygous δβ⁰ -thalassemia (n = 2), and carriers of the β-Hb variant (n = 3). Mutation analysis identified in addition to the Hb E, 8 different β-thalassemia mutations including codon 17 (A-T), codons 41/42 (-TTCT), NT-28 (A-G), codons 71/72 (+A), IVS1-1 (G-T), 3.4 kb deletion, an initiation codon (T-G) and IVS2-654 (C-T). Two δβ⁰ -thalassemia carriers (12.6 kb deletion) and three subjects with Hb Hope (β^136GGT-GAT ) were identified. Hematological features associated with these β-hemoglobinopathies were presented.

CONCLUSION

β-hemoglobinopathies in the Laos population is heterogeneous. This information is relevant for setting up a molecular diagnostics and can provide a basis for genetic counseling and enable prenatal diagnosis.

Hemoglobins F, A2 , and E levels in Laotian children aged 6-23 months with Hb E disorders: Effect of age, sex, and thalassemia types

Introduction

Determination of hemoglobins (Hbs) F, A_2, and E is crucial for diagnosis of thalassemia. This study determined the levels of Hbs F, A_2, and E in children aged 6‐23 months and investigated the effect of age, sex, and types of thalassemia on the expression of these Hbs.

Methods

A total of 698 blood samples of Laotian children including 272 non‐Hb E, 271 Hb E heterozygotes, and 155 Hb E homozygotes were collected. Hb profiles were determined using the capillary zone electrophoresis. Coinheritance of α‐thalassemia and the homozygosity for Hb E mutation were checked by PCR‐based assay.

Results

Children heterozygous and homozygous for Hb E had significantly higher Hb F and A₂ levels than non‐Hb E children (median Hb F = 1.1% for non‐Hb E group, 2.7% for Hb E heterozygotes, and 9.4% for Hb E homozygotes; median Hb A₂ = 2.6% for non‐Hb E group, 3.8% for Hb E heterozygotes, and 5.2% for Hb E homozygotes). The median Hb E levels were 21.9% for Hb E heterozygotes and 85.3% for Hb E homozygotes. Comparing within group, there was a statistically significant difference between children with and without an α‐gene defect for Hb A₂ and E, but not Hb F. Based on a multiple regression analysis, age and sex were significantly associated with the expression of Hb F and A₂ but not Hb E.

Conclusions

Our findings can guide the development of a diagnostic approach to thalassemia in children aged 6‐23 months.

Factors associated with anaemia and iron deficiency among women of reproductive age in Northeast Thailand: a cross-sectional study

Background

Anaemia and iron deficiency (ID) affect women of reproductive age globally and considered to be a major public health problem in developing countries. This study determines the prevalence of anaemia and ID among women of reproductive age in urban northeast Thailand and examined the relative contribution of various risk factors to anaemia and ID in this population.

Methods

Three hundred ninety-nine non-pregnant women, aged 18–45 years, from three universities in northeast Thailand participated in this cross-sectional study. Selected socio-demographic, history of blood loss, usual consumption of red meat and tea/coffee, and anthropometric data were collected. Complete blood count including haemoglobin (Hb) concentration, serum ferritin (SF), C-reactive protein (CRP), and thalassemia were determined. Multiple logistic regressions were applied to identify the risk factors of anaemia and ID.

Results

Overall, 370 participants were included for data analyses after excluding women with severe/intermedia thalassemia diseases and/or those with positive serum CRP. The prevalence of anaemia, ID, and iron deficiency anaemia (IDA) were 28.4, 28.4, and 13.2%, respectively. Women with thalassemia had a higher prevalence of anaemia but a lower prevalence of ID than the women without thalassemia. By multiple regression analysis, ID [adjusted OR (AOR) = 4.9, 95% CI = 2.8–8.3], two α-gene defects (AOR = 8.0, 95% CI = 3.0–21.3) and homozygous Hb E (AOR = 8.5, 95% CI = 3.0–24.3) were identified as the potential risk factors of anaemia. Further, the odds of ID were significantly higher among women who donated blood within the past 3 months (AOR = 6.7, 95% CI = 2.8–16.3), and had moderate to a high amount of blood loss during menstruation (AOR = 2.2, 95% CI = 1.3–3.9).

Conclusion

This study found a relatively high but differential prevalence of anaemia and ID among women of reproductive age with or without thalassemia. Only homozygous Hb E and two α-gene defects of thalassemia types and ID were the main factors contributing to anaemia. Recent blood donation, and moderate to a high amount of blood loss during menstruation were potential risk factors of ID in this population.

Dominant β-thalassaemia with unusually high Hb A2 and Hb F caused by βCD121(-G) (HBB:c.364delG) in exon 3 of β-globin gene

We describe a dominant β-thalassaemia caused by a deletion of G at nucleotide position 364 in exon 3 of the β-globin gene. The heterozygosity of this mutation was found in a 36-year-old Thai patient who had moderate hypochromic microcytic anaemia with haemolytic blood picture. Haemoglobin (Hb) analysis revealed relatively higher Hbs A₂ (6.8%) and F (4.7%) as compared with those of β⁰-thalassaemia (n=278) and β⁺-thalassaemia (n=55) carriers in our series. Secondary structure prediction of the elongated β-globin chain showed that the α-helix at the C-terminal is disrupted dramatically by the random coil and β-sheet, which should result in a highly unstable β-globin variant, undetectable in peripheral blood and a dominant clinical phenotypic feature.

A novel SNP rs11759328 on Rho GTPase-activating protein 18 gene is associated with the expression of Hb F in hemoglobin E-related disorders

Hemoglobin (Hb) F has a modulatory effect on the clinical phenotype of β-thalassemia disease. High expression of Hb F in Hb E-related disorders has been noted, but the mechanism is not well understood. We have examined the association of a novel SNP rs11759328 on ARHGAP 18 gene and other known modulators with a variability of Hb F in Hb E-related disorders. Genotyping of SNP rs11759328 (G/A) was performed based on high-resolution melting analysis. The rs11759328 (A allele) was shown to be significantly associated with Hb F levels (p < 0.05) in heterozygous and homozygous Hb E. High levels of Hb F in both heterozygous and homozygous Hb E were also found to be associated with SNPs in the study of other modifying genes including KLF 1 mutation, rs7482144 (Gγ-XmnI), rs4895441, rs9399137 of (HBS1L-MYB), and rs4671393 (BCL11A). Multivariate analysis showed that KLF1 mutation and SNP rs11759328 (GA) (ARHGAP18) modulated Hb F expression in heterozygous Hb E. For homozygous Hb E, this was found to be related to five modifying factors, i.e., KLF1 mutation, rs4895441 (GG), rs9399137 (CC), rs4671393 (AA), and rs4671393 (GA). These results indicate that a novel SNP rs11759328 is a genetically modifying factor associated with increased Hb F in Hb E disorder.

Thalassemia and Hemoglobinopathies in an Ethnic Minority Group in Northern Vietnam

This study assessed thalassemia and hemoglobinopathies in a group of the Tay ethnic minority. Participants included 289 women of reproductive-age who enrolled in a pilot screening program for thalassemia conducted at six communities of Thai Nguyen Province, northern Vietnam. Standard procedures including complete blood count (CBC), hemoglobin (Hb) and DNA analyses were performed for all samples. The prevalence of thalassemia in 289 Tay women was 15.6% (gene frequency 0.078) for α⁰-thalassemia (α⁰-thal), 10.0% (gene frequency 0.050) for α⁺-thal, 7.3% (gene frequency 0.036) for β-thalassemia (β-thal), 2.4% (gene frequency 0.012) for Hb Constant Spring [Hb CS; α142, Term→Gln, TAA>CAA (α2), HBA2: c.427T>C] and 1.7% (gene frequency 0.009) for Hb E [β26(B8)Glu→Lys, GAG>AAG; HBB: c.79G>A]. Further analysis of β-globin gene abnormalities identified four mutations including codons 41/42 (-TCTT) (HBB: c.126_129delCTTT), codon 17 (A>T) (HBB: c.52A>T), codons 71/72 (+A) (HBB: c.216_217insA), and -28 (A>G) (HBB: c.78A>G). The results hint at the remarkably high frequencies of severe forms of thalassemia that indicate a serious public health problem requiring further exploration, and most probably, also intervention within the country.

Molecular characteristics of α+-thalassemia (3.7 kb deletion) in Southeast Asia: Molecular subtypes, haplotypic heterogeneity, multiple founder effects and laboratory diagnostics

OBJECTIVE

The 3.7 kb deletion (-α^3.7) is the most common form of α⁺-thalassemia found in multiple populations which can be classified into three subtypes. In order not to mis-identify it, the molecular information within each population is required. We have addressed this in northeast Thai and Laos populations.

METHODS

Screening for α⁺-thalassemia was initially done on 1192 adult Thai subjects. In addition, 77 chromosomes of Thai newborns and 26 chromosomes of Laos with -α^3.7 α⁺-thalassemia were also examined. All subjects were screened for -α^3.7 α⁺-thalassemia and subtyped by PCR-RFLP assay. Exact deletion breakpoint of each -α^3.7 subtype was determined by DNA sequencing. α-Globin gene haplotypes were determined.

RESULTS

The proportions of -α^3.7 subtypes found in 216 Thai -α^3.7 chromosomes were 94.9% for -α^3.7I, 4.2% for α^3.7II and 0.9% for -α^3.7III. All 26 Laos -α^3.7 chromosomes were of -α^3.7I variety. At least six α-globin gene haplotypes were associated with the -α^3.7I α⁺-thalassemia.

CONCLUSION

All -α^3.7 subtypes were observed among Southeast Asian population. Haplotype analysis indicated a multiple origin of this common disorder in the region. A multiplex PCR assay has been developed for simultaneous detection of all subtypes of -α^3.7 α⁺-thalassemia as well as other α⁺-thalassemia found in the region including -α^4.2 α⁺-thalassemia, Hb Constant Spring and Hb Paksé.

EE score: an index for simple differentiation of homozygous hemoglobin E and hemoglobin E-β0-thalassemia

BACKGROUND

The objective of the study was to describe a formula based on hemoglobin (Hb)A2 and HbF levels for differentiation of homozygous HbE and HbE-β-thalassemia.

METHODS

A total of 1256 subjects suspected for homozygous HbE or HbE-β0-thalassemia were recruited at the ongoing thalassemia screening program at Khon Kaen University, Thailand. Hb analysis was done using capillary electrophoresis. Genotyping was based on DNA analysis. An arbitrary formula based on HbA2 and HbF was developed statistically for differentiation of the two conditions. Validation was carried out prospectively on another 139 subjects encountered at routine laboratory.

RESULTS

Among 1256 subjects, Hb and DNA analyses identified cases with homozygous HbE (n=1076, 85.7%), HbE-β0-thalassemia (n=140, 11.1%), HbE-δβ0-thalassemia (n=30, 2.4%) and unknown HbE-related disorder (n=10, 0.8%). An inverse correlation between the amounts of HbA2 and HbF in HbE-β0-thalassemia was observed. With differences in the amounts of HbA2 and HbF between the groups, an arbitrary score (7.3 HbA2+HbF) was developed where score above 60 indicated HbE-β0-thalassemia. Application of this score on another 139 subjects showed accurate prediction of HbE-β0-thalassemia with 100% sensitivity, 96.5% specificity, 85.7% positive predictive value and 100% negative predictive value. Successful application onto couples at risk was demonstrated.

CONCLUSIONS

An established score should prove useful in the differentiation of homozygous HbE and HbE-β0-thalassemia in routine setting and lead to a significant reduction in number of referring cases for molecular testing.

Molecular characterisation of haemoglobin E-Udon Thani (HBB:c.[79G>A;92+7A>G]): a novel form of Hb E-β-thalassaemia syndrome

Interaction of βE-globin gene with an in trans β-thalassaemia gene leads to thalassaemia syndrome, known as haemoglobin (Hb) E-β-thalassaemia disease, with variable clinical and haematological severity. Here, we reported for the first time the Hb E-β-thalassaemia syndrome caused alternatively by an in cis interaction of βE and a novel IVSI#7;A>G mutation, namely the Hb E-Udon Thani (HBB:c.[79G>A;92+7 A>G]). The syndrome was found in an adult Thai man (32) who was generally healthy but had an unexplained hypochromic microcytosis. Hb analysis identified heterozygous Hb E with very low Hb E expression (3.1%) and elevated Hb A2 (5.7%). Final diagnosis was made on DNA analysis, which confirmed a double mutation in a single β-globin gene of the patient. A multiplex allele-specific PCR assay was developed for use in the screening of this novel form of Hb E-β-thalassaemia in the population.

Whole Blood PCR for Rapid Screening of α0-Thalassemia

Hemoglobin Bart's hydrops fetalis (homozygous α⁰-thalassemia) is the most severe form of thalassemia in the Southeast Asian population. Fetuses with this disorder almost always die in utero or shortly after birth. Screening of α⁰-thalassemia carrier is therefore crucial. Currently, diagnosis of α⁰-thalassemia genes is done by DNA-based analysis which relies on DNA extraction. We have developed a simple screening format based on whole blood PCR assay. The method was validated on 198 specimens and the results show 100% concordance with a conventional gap-PCR on DNA specimens. The protocol could also be applied to amniotic fluid specimens in prenatal diagnostic testing. The assay developed should facilitate carrier screening and prenatal diagnosis of Hb Bart's hydrops fetalis syndrome in the region.

Effect of health education on severe thalassemia prevention and control in communities in Cambodia

Background

Severe thalassemia diseases are a major health problem in Southeast Asia. In Cambodia, there has never been a significant program for prevention or control of severe thalassemia. We, therefore, studied the effect of a health education program on severe thalassemia prevention and control in Phnom Penh, Cambodia.

Methods

A quasi-experimental study in several communities around Phnom Penh was done. The respective intervention and control group comprised 124 and 117 people, between 18 and 40 years of age, male and female. Pre- and post-tests using a validated and reliable questionnaire were performed in the intervention group and one test was done in the control group. A health education program was organized to give important information to the intervention group and, at the end of the process, to the control group. The outcomes were evaluations of their knowledge and attitude vis-à-vis severe thalassemia prevention and control, and participating in thalassemia screening.

Results

Among participants in the intervention group, 105 (84.7%) considered undergoing blood screening vs. 65 (55.6%) in the control group (p-value < 0.001). In the intervention group, the respective mean scores for knowledge and attitude to a prevention and control program for severe thalassemia before and after health education were 2.6 VS 6.5 (p-value < 0.001) and 4.6 VS 6.5 (p-value < 0.001).

Conclusions

The intention to undergo screening was significantly higher in the intervention group than the control group. Knowledge and attitude towards prevention and control of severe thalassemia was significantly improved in the intervention group. Health education clearly heightens awareness and improves consideration of screening for prevention and control of severe thalassemia.

Elevations of Thrombotic Biomarkers in Hemoglobin H Disease

BACKGROUND

Thalassemia is a group of hereditary hemoglobinopathies caused by decreased or absent synthesis of α and/or β globin chains. Studies have shown that hypercoagulability and thrombosis are common clinical symptoms in β-thalassemia, especially β-thalassemia intermedia, but little is known about in α-thalassemia. This study aims to examine phosphatidylserine (PS) levels, platelet activation, and coagulation markers in splenectomized (S) and nonsplenectomy (NS) patients with hemoglobin (Hb) H disease.

METHODS

The NS group comprised 20 patients (median age 15.0 years, range, 14-16.5 years), and the S group consisted of 11 patients (median age 16.4 years, range, 14-19.9 years) with Hb H disease; the control group consisted of 20 normal subjects. Hematological parameters were collected. Flow cytometry was used to measure PS exposure on red blood cells. The levels of intercellular adhesive molecule (ICAM)-1, tumor necrosis factor α (TNFα), β-thromboglobulin (TG) and prothrombin fragment 1 + 2 (F1.2) were determined using ELISA test kits.

RESULTS

Significant increases in the levels of PS, ICAM-1, TNFα, β-TG, and F1.2 were observed in both patient groups compared to normal controls (p < 0.01).

CONCLUSION

This observation indicates blood coagulation, endothelial injury, chronic low-grade inflammation, platelet activation, and thrombin generation are present in Hb H disease; these findings merit further assessment in a larger prospective cohort to establish possible links with thrombotic manifestations.

Novel interactions of two α-Hb variants with SEA deletion α0-thalassemia: hematological and molecular analyses

OBJECTIVES

To report the hematological and molecular features as well as diagnostic aspects of the hitherto un-described interactions of two rare α-globin chain variants with α⁰-thalassemia commonly found among Southeast Asian populations.

METHODS

The study was done on two adult Thai patients (P1 and P2) who had hypochromic microcytic anemia. Hb analysis was carried out using high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). Mutations were identified by PCR and related techniques.

RESULTS

Hb analysis of P1 using HPLC showed a normal Hb pattern, but CE demonstrated an abnormal peak at zone 7. DNA sequencing identified a CCG-CTG mutation at codon 95 of the α2 globin gene corresponding to the Hb G-Georgia [α95(G2)Pro → Leu(α2)] previously undescribed in the Thai population. In contrast, Hb analysis of P2 demonstrated an abnormal peak not fully separated from Hb A on HPLC, but not on CE. DNA analysis identified the rarely described Hb Nakhon Ratchasima [α63(E12)Ala → Val(α2)] mutation. Routine DNA analysis detected the SEA deletion α⁰-thalassemia in trans to the Hb variants in both cases. Hematological parameters were compared with those of patients with compound heterozygote for other α-globin variants and α⁰-thalassemia previously documented.

CONCLUSIONS

Identification of the patients confirmed that interaction of these rare Hb variants with α⁰-thalassemia does not lead to the Hb H disease. Differentiation of these two Hb variants from other clinically relevant hemoglobinopathies in a routine setting is, however, necessary. This can be accomplished using a combined Hb-HPLC and CE analysis followed by PCR-RFLP assays.

Evaluation of staff performance and interpretation of the screening program for prevention of thalassemia

Introduction

Thalassemia screening program has been implemented for years in Southeast Asia, but no external quality assessment program has been established. We have developed and initiated the proficiency testing (PT) program for the first time in Thailand with the aim to assess the screening performance of laboratory staff and their competency in interpretation of the screening results.

Materials and methods

Three PT cycles per year were organized. From the first to the third cycle of the PT scheme, a total number of participant laboratories increased from 59 to 67. In each cycle, 2 PT items (assigned as blood samples of the couple) were provided. Performance evaluation was based on the accuracy of screening results, i.e. mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and the dichlorophenolindophenol (DCIP) test for haemoglobin E, including the competency in interpretation of screening results and assessment of foetal risk. Performance was assessed by comparing the participants’ result against the assigned value.

Results

Of all 3 cycles, most laboratories reported acceptable MCV and MCH values. From the first to the third cycle, incorrect DCIP test and misinterpretation rates were decreased while incorrect risk assessment varied by cycle to cycle. Combining the accuracy of thalassemia screening and the competency in interpretation and risk assessment, approximately half of participants showed excellent performance.

Conclusion

Improved performance observed in many laboratories reflects the achievement and benefit of the PT program which should be regularly provided.

Co-inheritance of α0 -thalassemia elevates Hb A2 level in homozygous Hb E: Diagnostic implications

INTRODUCTION

Differentiation of homozygous hemoglobin (Hb) E with and without α⁰ -thalassemia is subtle on routine hematological ground. We examined in a large cohort of homozygous Hb E if the level of Hb A₂ is helpful.

METHODS

A total of 592 subjects with homozygous Hb E were recruited from ongoing thalassemia screening program. Additionally, five couples at risk of having fetuses with Hb Bart's hydrops fetalis who were homozygous Hb E were also investigated. Hb analysis was performed using capillary electrophoresis system. Globin genotypes were defined by DNA analysis.

RESULTS

Subjects were classified into four groups including pure homozygous Hb E (n=532), homozygous Hb E/α⁰ -thalassemia (n=48), Hb Constant Spring EE Bart's disease (n=8), and Hb EE Bart's disease (n=4). The levels of Hb A₂ were found, respectively, to be 4.97±0.69, 6.64±1.02, 4.86±0.87, and 7.60±1.04%. Among five couples at risk, α⁰ -thalassemia was identified in three subjects with Hb A₂ >6.0%.

CONCLUSIONS

Increased Hb A₂ level is a useful marker for differentiation of homozygous Hb E with and without α⁰ -thalassemia. This should lead to a significant reduction in number of referral cases of homozygous Hb E for molecular testing of α⁰ -thalassemia in routine practice.

Genetic origin of α0-thalassemia (SEA deletion) in Southeast Asian populations and application to accurate prenatal diagnosis of Hb Bart's hydrops fetalis syndrome

α⁰-thalassemia of SEA deletion (—^SEA) is common among Southeast Asian and Chinese. Using haplotype and phylogenetic analyses, we examined the origin of this defect in Southeast Asian populations. Study was done on both normal and α⁰-thalassemia alleles in 3 ethnic groups including 96 Thai, 52 Laotian and 21 Cambodian. Five SNPs encompassing the (—^SEA) including (rs3760053 T>G), (rs1211375 A>C), (rs3918352 A>G), (rs1203974 A>G) and (rs11248914 C>T) were examined using high-resolution melting assays. It was found that 94.0% of Thai, 100% of Laotian and 100% of Cambodian α⁰-thalassemia alleles were linked to the same haplotype: the haplotype H4 (AAGC), representing an Asian specific origin. An G allele of the (rs3760053) was found to be in strong linkage disequilibrium with the α⁰-thalassemia allele in these populations. A multiplex PCR assay was developed to detect simultaneously the (—^SEA) allele and genotyping of a linked (rs3760053) to improve accuracy of prenatal diagnosis of α⁰-thalassemia. Application of this multiplex PCR assay for routine prenatal diagnosis of α⁰-thalassemia in 12 families revealed a 100% concordant result with conventional gap-PCR assay. Therefore, a single genetic origin is responsible for the spread and high prevalence of the (—^SEA) in the region. The multiplex PCR assay developed should provide a double-check PCR system for more accurate diagnosis and allow the monitoring of possible maternal contamination at prenatal diagnosis of this important genetic disorder.

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.

PILOT SCREENING PROGRAM FOR THALASSEMIA IN A COUNTRY WITH LIMITED RESOURCES: A COLLABORATION MODEL BETWEEN CLOSE NEIGHBORING COUNTRIES

Screening for thalassemia carriers should not only be conducted in middle-income countries but also can be possible in low-middle income countries, through cooperation of experienced professionals from middle income countries. We describe a collaborating model between two close neighboring countries in establishing such a screening program for thalassemia. After training and setting up of facilities, a total of 152 out of 187 hospital staff were screened as a pilot activity to encourage community participation. Referring system for sending blood samples to a reference center in Thailand was also established. Among 152 health staff, 12.5% α0-thal, 2% β-thal and 13% Hb E carriers were found. Applying thalassemia screening to 411 pregnant women and 71 spouses, 5 couples at risk of bearing a child of thalassemia disease were identified. The thalassemia screening program has a sensitivity of 99.5%, specificity of 77%, positive predictive value of 73%, and negative predictive value of 99.5%. Thus, it is possible to operate a thalassemia screening program with acceptable performance in a low-middle income country (Lao People’s Democratic Republic) with the cooperation of a referral center located within close proximity in a middle income country (Thailand).

Screening of (-SEA) α-thalassaemia using an immunochromatographic strip assay for the ζ-globin chain in a population with a high prevalence and heterogeneity of haemoglobinopathies

AIMS

The presence of the ζ-globin chain is a good marker of (--^SEA) α⁰-thalassaemia. We evaluated an immunochromatographic (IC) strip assay for ζ-globin in screening for (--^SEA) α⁰-thalassaemia in a population with a high prevalence and heterogeneity of haemoglobinopathies.

METHODS

The study was carried out on 300 screen positive blood samples of Thai individuals. The IC strip assay for the ζ-globin chain was performed on all samples. The results were interpreted with thalassaemia genotyping using standard haemoglobin and DNA analyses.

RESULTS

Several thalassaemia genotypes were noted. Among the 300 subjects investigated, 79 had a positive IC strip assay for ζ-globin and (--^SEA) α⁰-thalassaemia was identified in 40 of them. No (--^SEA) α⁰-thalassaemia was detected in the remaining 39 samples with a positive IC strip test result or in the 221 samples with a negative IC strip test result. Further DNA analysis identified α⁺-thalassaemia in 25 of the 39 (--^SEA) α⁰-thalassaemia negative samples. Using this IC strip assay in combination with a conventional screening protocol for (--^SEA) α⁰-thalassaemia could provide sensitivity and specificity of 100% and 90.4%, respectively.

CONCLUSIONS

IC strip assay for ζ-globin is simple, rapid and does not require sophisticated equipment. Use of this test in addition to the existing screening protocol could detect potential (--^SEA) α⁰-thalassaemia leading to a significant reduction in the workload of DNA analysis. This could be used in areas where haemoglobinopathies are prevalent and heterogeneous but molecular testing is not available.

FLT3-ITD Mutations in Acute Myeloid Leukemia Patients in Northeast Thailand

The FLT3-ITD mutation is one of the most frequent genetic abnormalities in acute myeloid leukemia (AML) where it is associated with a poor prognosis. The FLT3-ITD mutation could, therefore, be a potential molecular prognostic marker important for risk-stratified treatment options. We amplified the FLT3 gene at exon 14 and 15 in 52 AML patients (aged between 2 months and 74 years) from 4 referral centers (a university hospital and 3 regional hospitals in Northeast Thailand), using a simple PCR method. FLT3-ITD mutations were found in 10 patients (19.2%), being more common in adults than in children (21.1% vs. 14.3%) and more prevalent in patients with acute promyelocytic leukemia (AML-M3) than AML-non M3 (4 of 10 AML-M3 vs. 6 of 42 AML- non M3 patients). Duplication sequences varied in size-between 27 and 171 nucleotides (median=63.5) and in their location. FLT3-ITD mutations with common duplication sequences accounted for a significant percentage in AML patients in northeastern Thailand. This simple PCR method is feasible for routine laboratory practice and these data could help tailor use of the national protocol for AML.

Hemoglobin Constant Spring among Southeast Asian Populations: Haplotypic Heterogeneities and Phylogenetic Analysis

Background

Hemoglobin Constant Spring (Hb CS) is an abnormal Hb caused by a mutation at the termination codon of α2-globin gene found commonly among Southeast Asian and Chinese people. Association of Hb CS with α°-thalassemia leads to a thalassemia intermedia syndrome commonly encountered in the region. We report chromosome background and addressed genetic origins of Hb CS observed in a large cohort of Hb CS among Southeast Asian populations.

Materials and Methods

A study was done on 102 Vietnamese (aged 15–49 year-old) and 40 Laotian (aged 18–39 year-old) subjects with Hb CS and results compared with 120 Hb CS genes in Thailand. Hematological parameters were recorded and Hb analysis was performed using capillary electrophoresis. Hb CS mutation and thalassemia genotypes were defined by DNA analysis. Six DNA polymorphisms within α-globin gene cluster including 5’Xba I, Bgl I, Inter-zeta HVR, AccI, RsaI and αPstI 3’, were determined using PCR-RFLP assay.

Results

Nine different genotypes of Hb CS were observed. In contrast to the Thai Hb CS alleles which are mostly linked to haplotype (+—S + + -), most of the Vietnamese and the Laotian Hb CS genes were associated with haplotype (+—M + + -), both of which are different from that of the European Hb CS.

Conclusions

Hb CS is commonly found in combination with other thalassemias among Southeast Asian populations. Accurate genotyping of the cases requires both hematologic and DNA analyses. At least two independent origins are associated with the Hb CS gene which could indirectly explain the high prevalence of this Hb variant in the region.