Analysis of fetal blood using capillary electrophoresis system: a simple method for prenatal diagnosis of severe thalassemia diseases

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.

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.

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.

Electrophoresis features and genotypes of Hb bart's hydrops fetalis

Hydrops fetalis syndrome (Hb Bart's disease) is one of the common fetal development abnormalities and the most severe form of α-thalassemia. It causes fetal death during the third trimester or shortly after birth. The aim of this study is to investigate the feature of Hb Bart's disease by Capillary electrophoresis (CE) and its genotypes. A total of 38 cases of suspected fetal Hb Bart's disease were analyzed by B-ultrasound and CE, including 17 with 24-28 weeks of pregnancy, 9 with 29-32 weeks of pregnancy, and 12 with 33-38 weeks of pregnancy. All cases were then identified by DNA analysis. The minimum concentration of Hb Bart's was 72.2% and the highest 90.9%. Hb Bart's fraction increased while that of Hb Portland decreased with the duration of pregnancy. In order to avoid serious maternal morbidity, it is necessary to diagnose Hb Bart's disease as soon as possible and CE can be used as a method of rapid diagnosis.

Noninvasive prenatal screening test for compound heterozygous beta thalassemia using an amplification refractory mutation system real-time polymerase chain reaction technique

We propose using a modified amplification refractory mutation system real-time polymerase chain reaction (ARMS RTPCR) technique to exclude the invasive prenatal diagnosis for a non-paternally inherited beta thalassemia mutation in couples atrisk for having a baby with CHBT. The ARMS RT-PCR method was performed for 36 at-risk couples by using isolated fetal cell-free DNA from maternal plasma. The modified ARMS RT-PCR primers targeted one of the following paternally inherited beta thalassemia mutation: -28 A→G, CD17 A→T, CD 26 G→A, IVS1-1 G→T and CD 41-42 -CTTT. The method could be successfully employed for NIPST starting with the 7^th week of gestation. The results showed that 19 pregnant women were negative for PIBTM (53%). After an on-track and on-time of one year, including postnatal thalassemia blood tests, none of the babies showed symptoms or signs of beta thalassemia disease. We concluded that the modified ARMS RT-PCR method was an accurate, cost-effective and feasible method for use as a NIPST for at-risk couples with the potential of having a baby with CHBT.

Antenatal screening for haemoglobinopathies: current status, barriers and ethics

Sickle cell disease (SCD) and thalassaemia are genetic disorders that are caused by errors in the genes for haemoglobin and are some of the most common significant genetic disorders in the world, resulting in significant morbidity and mortality. Great disparities exist in the outcome of these conditions between resource- rich and resource-poor nations. Antenatal screening for these disorders aims to provide couples with information about their reproductive risk and enable them to make informed reproductive choices; ultimately reducing the likelihood of children being born with these conditions. This review provides an overview of the current status of antenatal, pre-marital and population screening of SCD and thalassaemia in countries with both high-and low prevalence of these conditions, methods of screening in use, and discusses some of the pitfalls, ethical issues and controversies surrounding antenatal screening. It also discusses outcomes of some screening programmes and recognises the need for the establishment of antenatal screening in areas where their prevalence is highest; namely sub-Saharan Africa and India.

Prevalence of Thalassemia among Newborns: A Re-visited after 20 Years of a Prevention and Control Program in Northeast Thailand

Background

To provide accurate prevalence information of thalassemia in northeast Thailand, authors performed thalassemia screening in newborns after 20 years implementation of a prevention and control program.

Methods

Study was done on 350 cord blood specimens collected consecutively at Maternal and Child Hospital, Regional Health Promotion Center 7, Khon Kaen, Thailand. All kinds of α- and β-thalassemias were identified using combined hemoglobin (Hb) and DNA analyses.

Results

Among 350 newborns examined, subjects with thalassemia genes were identified in 184 (52.6%) cases with as many as 22 different genotypes. The most prevalent one was Hb E (39.1%). The incidence of 3.1% α⁰-thalassemia, 25.9% α⁺-thalassemia, 5.4% Hb Constant Spring and 1.4% of Hb Paksé were encountered. Heterozygous β-thalassemia was found in 2 cases (0.6%). Hb capillary electrophoresis could demonstrate Hb E in all cases with Hb E and detected different levels of Hb Bart’s for different α-thalassemia genotypes but not in all cases with α-thalassemia. No newborn with severe thalassemia diseases was encountered.

Conclusion

This study reveals that α-thalassemia, β-thalassemia, and Hb E carriers as well as complex thalassemia syndromes are still prevalence and indicates a need for continuing a prevention and control program in the region.

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.

Invasive prenatal diagnosis of fetal thalassemia

Thalassemia is the most common monogenic inherited disease worldwide, affecting individuals originating from many countries to various extents. As the disease requires long-term care, prevention of the homozygous state presents a substantial global disease burden. The comprehensively preventive programs involve carrier detections, molecular diagnostics, genetic counseling, and prenatal diagnosis. Invasive prenatal diagnosis refers to obtaining fetal material by chorionic villus sampling (CVS) at the first trimester, and by amniocentesis or cordocentesis at the second trimester. Molecular diagnosis, which includes multiple techniques that are aimed at the detection of mutations in the α- or β-globin genes, facilitates prenatal diagnosis and definitive diagnosis of the fetus. These are valuable procedures for couples at risk, so that they can be offered options to have healthy offspring. According to local practices and legislation, genetic counseling should accompany the invasive diagnostic procedures, DNA testing, and disclosure of the results. The most critical issue in any type of prenatal molecular testing is maternal cell contamination (MCC), especially when a fetus is found to inherit a particular mutation from the mother. The best practice is to perform MCC studies on all prenatal samples. The recent successful studies of fetal DNA in maternal plasma may allow future prenatal testing that is non-invasive for the fetus and result in significant reduction of invasive diagnostic procedures.

Cognitive Performance and Iron Status are Negatively Associated with Hookworm Infection in Cambodian Schoolchildren

Soil-transmitted helminth (STH) infection has been associated with lower cognitive performance of schoolchildren. To identify pathways through which STH infection might affect school performance, baseline data from a large rice-fortification trial in Cambodian schoolchildren were used to investigate associations between STH infection, micronutrient status, anemia, and cognitive performance. Complete data on anthropometry, cognitive performance, and micronutrient status were available for 1,760 schoolchildren, 6-16 years of age. STH infection was identified using Kato-Katz, whereas cognitive performance was assessed using Raven's Colored Progressive Matrices (RCPM), block design, and picture completion. STH infection was found in 18% of the children; almost exclusively hookwork infection. After adjusting for age and gender, raw cognitive test scores were significantly lower in hookworm-infected children (-0.65; -0.78; -2.03 points for picture completion, RCPM, and block design, respectively; P < 0.05 for all). Hookworm infection was associated with iron status (total body iron), but not with vitamin A and zinc status, nor with inflammation or anthropometry. Body iron was negatively associated with increased intensity of hookworm infection (R = 0.22, P < 0.001). Hookworm infection in Cambodian schoolchildren was associated with lower cognitive performance, an effect most likely mediated through lower body iron. Interventions that are more effective against hookworm infection are needed to contribute to better health and improvement of cognitive performance.

Routine screening for α-thalassaemia using an immunochromatographic strip assay for haemoglobin Bart's

Objective

To evaluate an immunochromatographic (IC) strip assay for Hb Bart's as a routine screening test for α-thalassaemia in area with a high prevalence of thalassaemia and haemoglobinopathies.

Methods

A total of 300 adult screen positive blood specimens were collected at an ongoing thalassaemia screening programme in northeast Thailand. Routine screening was done using red blood cell indices, osmotic fragility, and dichlorophenolindophenol tests. The IC strip assay for haemoglobin Bart's was performed on all samples. The result was evaluated against thalassaemia genotypes determined using standard haemoglobin and DNA analyses.

Results

Of 300 subjects investigated, Hb and DNA analyses identified 32 with normal genotype. The remaining subjects carried thalassaemia with as many as 16 different genotypes. Hb Bart's was detected in all cases, with several α0-thalassaemia (SEA type) related disorders. Of cases with α+-thalassaemia, 86.1% showed a positive result; 100 out of 103 Hb E carriers, all homozygous Hb E and β-thalassaemia trait were negative. Nine out of 17 cases with β-thalassaemia/Hb E disease, and one case of double heterozygote for Hb Q-Thailand and Hb E returned positive results. The overall sensitivity and specificity of the IC strip assay for detecting α0-thalassaemia were 100% and 73.1%, respectively.

Conclusion

The results showed a high sensitivity for screening for α0-thalassaemia using IC strip assay for Hb Bart's. This simple method, used in combination with conventional screening protocols, should lead to a significant reduction in the number of referral cases for DNA analysis. Cost effectiveness in each population should be taken into consideration.

Rapid Flow cytometric prenatal diagnosis of primary immunodeficiency (PID) disorders

OBJECTIVES

Primary Immunodeficiency diseases (PID) are a heterogeneous group of inherited disorders of immune system. Immunophenotypic evaluation of PIDs using flowcytometry provides important clues for diagnosis of these disorders, though confirmation requires identification of underlying molecular defects. Prenatal diagnosis (PND) forms an important component of management in families affected with severe PID. However, molecular diagnostic facilities for each of these diseases are not available and may not be possible to perform in all cases. In such scenario we opted for phenotypic prenatal diagnosis by cordocentesis for families with index case having immunophenotypically well characterized PID.

METHODS

Normal reference ranges of lymphocyte subsets, CD 18/CD11 integrins on leukocytes, MHC class II expression and oxidative burst activity of fetal neutrophils at 18 weeks of gestation were previously established on 30 cord blood samples. PND was performed in 13 families with PIDs. Maternal contamination was ruled out by VNTR analysis.

RESULTS

Out of 13 fetuses, nine were found to be unaffected (three cases with leukocyte adhesion deficiency (LAD-I), four cases with severe combined immunodeficiency diseases (SCID), one with X-linked agammaglobulinemia (XLA), and one with chronic granulomatous disease (CGD)] and three were found to be affected (one with T-B+NK-SCID, one with MHC class II deficiency and one with LAD-I). Diagnosis was confirmed by testing the cord blood samples after delivery and further follow-up of the children. In one family diagnosis could not be offered due to maternal contamination. No procedure related complications were observed.

CONCLUSION

Flowcytometry offers rapid and sensitive method for prenatal diagnosis and genetic counseling for selected phenotypically well characterized PID in cases where molecular diagnostic facilities are not available.

Birth of children with severe β-thalassemia at a tertiary obstetric hospital: what are the reasons behind it?

OBJECTIVE

To find reasons for the births of severe β-thalassemia at a tertiary obstetric hospital in mainland China.

METHODS

All cases with confirmed diagnosis of β-thalassemia major were included from 1 January 2007 to 31 December 2011. The main clinical characteristics of the affected pregnancies were reviewed, including maternal reproductive history, prenatal care in the current pregnancy, the gestation of pregnancy at the time of booking, and availability of husbands for a screen test.

RESULTS

A total of nine cases of β-thalassemia major were identified at birth during the study period. The reasons for no prenatal diagnosis included unavailability of the father for a test in four cases, unacceptability of the invasive procedure in two cases, absence of prenatal care in two cases, and nonpaternity in one case.

CONCLUSION

The effectiveness in control of the disease is not only associated with the model itself but also the factors playing against the model. The identification of the main reasons for the birth of severe thalassemia might help to find room for improvement in clinical practice.

Is the poly A (T>C) mutation a causative factor for misdiagnosis in second trimester prenatal diagnosis of β-thalassemia by fetal blood analysis on high performance liquid chromatography?

We report the problems in diagnosis faced by two families referred for prenatal diagnosis of thalassemia where cordocentesis and fetal blood analysis by high performance liquid chromatography (HPLC) had to be done. The Hb A levels of the fetal blood measured by HPLC on the VARIANT™ Hemoglobin Testing System were 1.2 and 6.7%, respectively, suggestive of a heterozygous β-thalassemia (β-thal) fetus in the first case and a normal fetus in the second case. In one family, one of the parents had a borderline Hb A(2) level and in the other, one parent had normal RBC indices. However, DNA sequencing, done later, showed that in the first case the fetus was a compound heterozygote for the IVS-I-5 (G>C) and the polyadenylation signal site [poly A (T>C)] mutation, while in the second case, the fetus was homozygous for the poly A mutation. This emphasizes that characterization of β-thal mutations must be done whenever one of the parents has a borderline Hb A(2) level or normal RBC indices, and one should not rely on fetal blood analysis by HPLC for prenatal diagnosis of β-thal so as to avoid misdiagnosis.

Evaluation of the URIT-2900 automated hematology analyzer for screening of thalassemia and hemoglobinopathies in Southeast Asian populations

BACKGROUND

The effectiveness of the URIT-2900 Hematology Analyzer for screening of hemoglobinopathies commonly found in Southeast Asian populations was examined.

METHODS

Appropriate cut-off values of MCV and MCH for screening of α(0) and β thalassemias were derived from the receiver operator characteristic curve conducted initially on 279 subjects with various thalassemia genotypes. Validation was performed additionally in a cohort of another unrelated 313 subjects.

RESULTS

The best cut off values of MCV and MCH were found to be 78fL and 27pg, respectively. Using these cut off values in combination with the dichlorophenolindophenol test in screening of α(0) thalassemia, β thalassemia and Hb E in a cohort study revealed 100% sensitivity, 79.6% specificity, 80.0% positive predictive value and 100% negative predictive value.

CONCLUSION

The combined blood cell counting using the URIT-2900 Automated Hematology Analyzer and dichlorophenolindophenol test is suitable for population screening of thalassemia and hemoglobinopathies in Southeast Asia.

Anemia, iron deficiency and thalassemia among adolescents in Northeast Thailand: results from two independent surveys

The prevalence of adolescent anemia, iron deficiency and thalassemia were examined in 2 provinces of northeast Thailand. Blood specimens were collected from adolescent subjects aged 15-17 years in 2 areas; 185 (85 males and 100 females) in Mukdahan province and 313 (116 males and 197 females) in Roi-Et. RBC parameters, serum ferritin levels, Hb and DNA analyses for the identification of common thalassemia genes in Thailand were investigated. The prevalences of anemia were found to be 21.1% (8.1 in male and 13.0 in female) and 16.6% (8.9 in male and 7.7 in female) in Mukdahan and Roi-Et province, respectively. Iron deficiency was observed to be 24.3% in Mukdahan and 14.7% in Roi-Et. Various types of thalassemia were identified in 62.2 and 58.8% of the subject populations, respectively. The proportions of iron deficiency, thalassemia and combined thalassemia and iron deficiency among anemic subjects were 10.2, 53.8 and 30.8% in Mukdahan, and 7.7, 67.3 and 9.6% in Roi-Et. Hematological characteristics were analyzed and are presented. It is concluded that thalassemia and hemoglobinopathies rather than iron deficiency are major causes of adolescent anemia which should be taken into account in public health strategies for the control of anemia in the region.

Prevention of severe thalassemia in northeast Thailand: 16 years of experience at a single university center

OBJECTIVE

To demonstrate the performance of thalassemia prevention in northeast Thailand during 1993-2008.

METHODS

Retrospective data from 1422 at-risk couples who attended from January 1993 to December 2008 were studied. All couples were suspected at-risk couples based on initial screening using standard protocols. Three thalassemia carrier types including alpha(0)-thalassemia, beta-thalassemia and hemoglobin E were identified using standard methods. Data on prenatal diagnosis were collected.

RESULTS

Of the 1422 positive-screened couples, 1254 (88.2%) were diagnosed as true-positive couples. After DNA analysis, 968 of 1254 (77.2%) resulted at risk for three types of severe conditions being hemoglobin E-beta-thalassemia disease (640/968, 66.1%), homozygous alpha(0)-thalassemia (304/968, 31.4%) and homozygous beta-thalassemia (11/968, 1.1%). The remaining 1.3% of the couples were at risk for more than one disease. After genetic counseling, prenatal diagnosis was performed on 756 couples (78.1%). The proportions of affected fetuses, thalassemia carriers and unaffected fetuses were 26.9, 50.0 and 23.0%, respectively.

CONCLUSION

Implementation of a prevention and control program accompanying with a referral system for prenatal diagnosis is technically feasible in northeast Thailand and a large number of severe thalassemia diseases have been prevented during the past 16 years of operation.

Hemoglobin Q-Thailand related disorders: origin, molecular, hematological and diagnostic aspects

We describe the molecular and hematological profiles of thalassemia syndromes caused by interactions of hemoglobin (Hb) Q-Thailand [α74(EF3) Asp-His] and various hemoglobinopathies found in 52 unrelated adult Thai subjects. Ten genotypes including several previously undescribed conditions were observed, which were classified into 4 groups. Group I included 26 Hb Q-Thailand heterozygotes and a homozygotous subject. Group II included subjects with Hb Q-Thailand and other α-thalassemia alleles in trans including 1 compound Hb Q-Thailand/α(+)-thalassemia (-α(3.7)), 2 Hb Q-Thailand/Hb Constant Spring disease and 6 Hb H/Q-Thailand disease. The average levels of Hb Q-Thailand were found to be 29.8%, 82.3%, 34.7%, 49.2-49.3% and 79.4%, respectively. Both Hbs Bart's and H were observed in addition to Hb Q-Thailand in all 6 cases with Hb Q-H disease but not in a homozygous Hb Q-Thailand. Group III included 7 double heterozygotes for Hb Q-Thailand/Hb E, 3 Hb Q-Thailand/Hb E/α(+)-thalassemia (-α(3.7)), 3 heterozygous Hb Q-Thailand/homozygous Hb E and 1 triple heterozygote for Hb Q-Thailand/Hb Constant Spring/Hb E. In this group, Hbs E (α(A)(2)β(E)(2)), Q-Thailand (α(QT)(2)β(A)(2)) and QE (α(QT)(2)β(E)(2)) were observed on both HPLC and capillary electrophoresis. The Hb QE, rather than Hb Q-Thailand, was detected in all 3 cases with heterozygous Hb Q-Thailand and homozygous Hb E. The remaining two cases in group 4 were double heterozygotes for Hb Q-Thailand and β(0)-thalassemia in which Hb Q-Thailand, elevated Hb A(2) (α(A)(2)δ(2)), and Hb QA(2) (α(QT)(2)δ(2)) were detected. DNA analysis identified the Hb Q-Thailand mutation (α74: GAC-CAC) and the linked (-α(4.2)) in all cases. Analysis of α-globin gene haplotype provided the first evidence of a single origin of this Hb variant in Thai population.