Hb Constant Spring Research Articles

A large cohort of Hb H disease in northeast Thailand: A molecular revisited, diverse genetic interactions and identification of a novel mutation

Background and aimsTo update the molecular characteristics of α-thalassemia in northeast Thailand, the molecular basis and genetic interactions of Hb H disease were examined in a large cohort of patients. Materials and methodsA study was done on 1,170 subjects with Hb H disease and various genetic interactions encountered during 2009–2023. Hb and DNA analyses were carried out. ResultsAs many as 40 genotypes with several known, previously undescribed, and novel mutations were observed. These included 698 subjects (59.8 %) of Hb H disease, 357 (30.6 %) with EABart’s disease, 63 (5.4 %) with EEBart’s disease, 18 (1.7 %) with abnormal Hbs, 17 (1.5 %) with β-thalassemia, and 4 (0.4 %) with EFBart’s or EFABart’s disease. The molecular basis of 13 subjects (1.1 %) remains unknown. The α0-thalassemia included --SEA (n = 1,139, 97.4 %) and --THAI (n = 21, 1.8 %). Two rare mutations were identified in 3 subjects (0.3 %) with --SA and --CR deletions. For α+-thalassemia, −α3.7 kb del (n = 626, 53.5 %), Hb Constant Spring (n = 415, 35.5 %), −α4.2 kb del (n = 44, 3.8 %), Hb Paksé (n = 36, 3.1 %), and Hb Q-Thailand (n = 19, 1.6 %), were detected. Ten rarer α+-thalassemia were identified, including a novel mutation, namely the Hb Chumphae (HBA2:c.32T>A). The Hb H-Lansing-Ramathibodi, Hb H-Jax, and Hb H-Chumphae are hitherto undescribed in this region. PCR-based diagnostic methods for these α-thalassemia defects were described. ConclusionsThis study confirms the diverse heterogeneity and genetic interactions causing Hb H disease in northeast Thailand. The results should prove useful for laboratory diagnosis and genetic counseling of this genetic disorder in the region.

Fetal Anemia in Northern Thailand: Etiologies and Outcomes

OBJECTIVE In Southeast Asia, hemoglobin (Hb) Bart’s disease is the primary cause of fetal anemia, although other causes are increasingly being identified. This study aimed to characterize the etiologies and outcomes of fetal anemia in northern Thailand. METHODS A retrospective chart review was conducted, involving pregnant women who attended antenatal care at Chiang Mai University Hospital between 2014 and 2021 and had a diagnosis by ultrasound findings of fetal anemia, or a fetal diagnosis of Hb Bart’s disease or other known hereditary anemias. RESULTS Among 71 fetuses from 64 pregnancies, 45 (63.4%) had Hb Bart’s disease. Twelve cases (16.9%) of fetal anemia were from other causes, including three cases of homozygous Hb Constant Spring, three cases of hereditary pyropoikilocytosis, one case of suspected red cell membrane disorder, one case each of Rh(D) alloimmunization, Hb H/Hb Pakse disease, transient abnormal myelopoiesis, syphilis infection, and one of unknown cause. All of the seven sets of twins (19.7%) had twin-to-twin transfusion syndrome (TTTS). Intrauterine transfusion was given in four cases of fetal hemolytic anemia which rendered good outcomes. Overall, 12 cases (16.9%) survived beyond the neonatal period. CONCLUSIONS Hb Bart’s disease remains the leading cause of fetal anemia in northern Thailand. Increasingly, frequently diagnosed causes include hemoglobinopathies and red cell membrane disorders.

Hematological Profile of Hb Adana Among High School Students in Northeast Peninsular Malaysia.

Background Hb Adana is a non-deletional alpha (α)-thalassaemia variant resulting from mutations in α1- or α2-globin codon 59 (αCD59), leading to the production of unstable α-globin. Clinical manifestations can vary from silent carrier status to dependence on blood transfusions, hepatosplenomegaly, skeletal deformities, and spinal cord compression. Despite the significance of Hb Adana inheritance, studying this variant poses challenges due to the scarcity of molecular tests and the potential for routine diagnoses to be overlooked. This study aims to investigate the prevalence of Hb Adana among local high school students and assess the hematological parameters and hemoglobin analysis of Hb Adana in Malaysia. Methodology This retrospective study analyzed 13,721 blood samples collected from high school students participating in Malaysia's National Thalassaemia Screening Program at Hospital Raja Perempuan Zainab II (HRPZ II). Deletional α-thalassaemia was detected using multiplex gap-polymerase chain reaction (PCR), while common non-deletional α-thalassaemia was identified using multiplex amplification refractory mutation system (ARMS) PCR. Data were extracted from the HRPZ II database for analysis. Results Among the participants, 2327 individuals were found to have either common deletional (n=1037, 44.6%) or non-deletional (n=1290, 55.4%) α-thalassaemia. Hb Constant Spring was the most prevalent non-deletional α-thalassaemia, accounting for 53.03% of cases. Thirty-one participants (1.33%) exhibited αCD59α/αα, and one (0.04%) had αCD59α/-α3.7. Among the 32 subjects with Hb Adana, 87.5% were Malay, and 12.5% were Orang Asli. Additionally, seven cases of HbE/Hb Adana co-inheritance were identified. Hemoglobin levels in heterozygous Hb Adana individuals ranged from mild anemia to normal, between 95 g/L and 153 g/L. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were approximately 73 fL and 23 pg, respectively. Conclusion This study delineates the distribution ofα-thalassaemia mutation patterns among high school students in Kelantan, Northeast Peninsular Malaysia. Our findings indicate that Hb Adana is rare in our region and co-inheritance with an α-gene deletion results in α+-thalassaemia and with HbE, α0-thalassaemia. All heterozygous Hb Adana individuals exhibited low MCVs and MCHs.

Non-transfusion dependent HbE/βO-thalassemia as the results of co-existent SEA-αO thalassemia, Hb Constant Spring, and XmnI-Gγ site: Thai family studies

Background: Four university students of northern Thai descent were found to be HbE/βO-thalassemia. However, they all had a mild form of this disease, categorized as Non-Transfusion Dependent Thalassemia. Objectives: To analyze involvement of types of β-globin mutations, α-thalassemia, and XmnI-Gγ site in mild clinical symptoms observed in four Thai non-transfusion dependent HbE/βO-thalassemia cases. Materials and methods: EDTA blood samples were collected from the patients and their family members after signing the informed consent. Automated complete blood count with blood smear examination, hemoglobin typing, molecular analysis for α and β-globin mutations, β-globin gene haplotypes, and XmnI-Gγ site were performed on all blood samples. In addition, nucleotide sequencing of β-globin gene and globin chain separation were performed for patient#3 and their parents. Results: The first three patients had hemoglobin levels ranging 8.5-11.2 g/dL, while the fourth patient had hemoglobin level of 6.7 g/dL. The first and fourth patients were compound heterozygote for βE (HBB:c.79G>A) and β17 (HBB:c.52A>T) alleles with typical hemoglobin pattern of EF. The second patient was compound heterozygote for βE and β41/42 (HBB:c.126_129delCTTT) alleles also with typical hemoglobin pattern of EF. The third patient was compound heterozygote of βE and βIVS1-1(HBB:c.92+1G>T), however, with atypical hemoglobin pattern of EE. Family analysis found co-inheritance of Hb Constant Spring (HBA2:c.427T>C) and the XmnI-Gγ site (T at rs7482144) in the first two patients, of SEA-αO thalassemia (NG_000006.1:g.26264_45564del19301) and XmnI-Gγ site in the third patient, and of only XmnI-Gγ site in the fourth patient. Conclusion: These family studies proved the fact that co-existence of SEA-αO thalassemia and Hb Constant Spring in HbE/βO-thalassemia could lead to mild clinical severity. Minimal effect of XmnI-Gγ site on clinical symptoms of this disease was emphasized. This information should be useful in prenatal diagnosis of HbE/β-thalassemia.

Detection of Non-Deletional Αlpha Thalassaemia in Hospital Tengku Ampuan Rahimah, Klang, Malaysia

Background: To date, more than 70 variants of non-deletional mutations associated with α-thalassaemia have been recognized and recorded, showcasing the diverse genetic manifes-tations of the condition. Objective: This study is to provide data on the non-deletional alpha (α) thalassaemia cases at Hospital Tengku Ampuan Rahimah (HTAR), Klang, Selangor and to compare the hematological parameters (Hb, RBC, MCH, MCV, MCHC) of non-deletional α thalassaemia with the deletional variant. Methods: This was a cross-sectional study involving data extraction from the HTAR hematology laboratory registry on confirmed thalassaemia cases via DNA analysis from January 2017 to December 2019. Hematological parameters were obtained from the laboratory database. Results: A total of 479 α thalassaemia cases were recruited, 98 (20.5%) were non-deletional type. Among these, 75 (76.5%) were hetero-zygous Hb CS, 17 (17.3%) heterozygous Hb Adana, 3 (3.1%) heterozygous Hb Quong Sze (QS) and 1 (1.0%) case each of compound heterozygous Hb Constant Spring (CS) and Hb Adana (αCSα/αCD59α), compound heterozygous Hb CS and -3.7kb deletion (αCSα /-α3.7) and compound heterozygous of Hb CS and SEA deletion (αCSα/--SEA). In the single and double gene mutated groups, there was no significant difference of hematological parameters be-tween the deletional and non-deletional groups. Among the non-deletional variants, there was a significant association between Hb, MCH and MCHC parameters and the number of mu-tated α gene. Conclusion: The result can update the data of non-deletional α thalassaemia.

Prime Editing of the α-Thalassemia Hb Constant Spring Mutation

Hemoglobin Constant Spring (HbCS) is the most common non-deletional α-thalassemic mutation and is an important cause of HbH-like disease in Southeast Asia. Although the α-globin is expressed from two copies of homologous genes ( HBA2 and HBA1), the constant spring (CS) mutation CD142 (UAA > CAA) occurs only in HBA2 gene that leads to the instability of both mRNA and protein in erythroid cells. The newly developed gene editing technology prime editors (PEs) can generate all types of substitutions, providing therapeutic potential in different types of diseases. However, the efficiency of primer editor in primary hematopoietic stem cells is still a big challenge and lack of study in the HbCS mutation. We first created the endogenous HbCS mutation in human umbilical cord blood-derived erythroid progenitor-2 (HUDEP-2) cells, providing as a model for prime editing optimization. The protein of α cs chain (a larger protein with extra 31 amino acids) was detected in the model cells with HBA2 bi-allelic CS mutation and normal HBA1, which exhibited the delay of expansion, higher apoptosis rate and altered erythroid maturation markers after induced differentiation. To correct the CS mutation for converting HbCS to HbA, we performed ex vivo delivery of mRNA encoding the prime editor together with a pegRNA and a nick guide RNA into the Hb CS HUDEP2 model cells and achieved the successful in-situ correction with an efficiency of 39.883±9.720% of CS alleles without enrichment, while no measurable editing in the same loci of HBA1 as evaluated by both Sanger sequencing and NGS. More importantly, the correction resulted in a significant decrease of α cs chain, thereby alleviated erythroid phenotype after induced maturation with reducing the apoptosis rate. After that, we collected the primary Hb H-CS patients derived CD34 + hematopoietic stem/progenitor cells (HSPCs) and confirmed that the defect on erythroid expansion, differentiation in Hb H-CS patients derived CD34 + HSPCs compared to the normal donor, especially demonstrated by lower enucleation rate and higher apoptosis. Moreover, the protein of α cs chain was detected in the erythroblast from Hb H-CS CD34+ HSPCs. We further successfully corrected the CS mutation in Hb H-CS patient derived CD34 + HSPCs with an efficiency of 23.68% by mRNA electroporation. At the same time, the editing efficiency was achieved with minimal generation of insertions and deletions and a low level of Cas9-dependent DNA off-target editing. Importantly, we observed an ~23% decrease of α cs chain protein and significant restoration of the enucleation defect from the differentiated erythroblast after PE correction in CD34 + HSPCs. In summary, these results suggests that the delivery of PE mRNA together with synthesized pegRNA and nick sgRNA can successfully achieve the in-situ correction in Hb HbCS mutation site in the model cells and the primary Hb H-CS patient derived CD34 + HSPCs. Our results provide proof of principle for prime editing for its therapeutic potential in directly and precisely correction of the Hb-CS mutation.

Effective screening of hemoglobin Constant Spring and hemoglobin Paksé with several forms of α- and β-thalassemia in an area with a high prevalence and heterogeneity of thalassemia using capillary electrophoresis

Background and aimsWe aimed to evaluate the efficiency of identification and quantification of hemoglobin (Hb) Constant Spring (CS) and Hb Paksé by capillary electrophoresis (CE). Materials and methodsBlood samples collected from 2057 patients were used for identifying and quantifying Hb by CE. Molecular analysis of α- and β-thalassemia, Hb CS, and Hb Paksé was performed. ResultsHb CS and Hb Paksé were identified in 573 samples (27.86%) with diverse genotypes. Thirty-eight samples (6.6%) showed no Hb CS peak. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of Hb CS by CE were 93.37, 95.96, 89.92, 97.40, and 95.24%, respectively. The amount of Hb CS in those carrying Hb CS was 0.2–6.5% which showed an increasing trend according to the number of defective α-globin genes, in contrast to Hb A2 levels, which decreased. Hb CS level ≥1.0% accurately excluded heterozygotes and that of ≥2.0% could identify homozygotes. ConclusionCE has the high potential for identifying and quantifying Hb CS and Hb Paksé, especially in an area with a high prevalence of thalassemia. Hb CS levels can be used as a potential marker to distinguish the genotype of individuals carrying Hb CS.

Essential genetic modifiers and their measurable impact in a community-recruited population analysis for non-severe hemoglobin E/β-thalassemia prenatal genetic counseling

The study aimed to identify essential phenotype-modulating factors among the pre-existence of several important ones and clarify their measurable impact on the clinical severity of hemoglobin (Hb) E/β-thalassemia in a community-recruited population analysis. This prospective study was designed to compare modifiers between community- (less or no symptoms) and hospital-recruited individuals with Hb E/β-thalassemia. The formerly included couples previously assessed for prenatal thalassemia at-risk status at 42 community and 7 referral hospitals in Thailand through on-site investigations between June 2020 and December 2021. The control included Hb E/β-thalassemia patients undergoing transfusions. The Mahidol score classified disease severity. Beta-globin, α0-thalassemia (-SEA, -THAI), α+-thalassemia (-α3.7, -α4.2), Hb Constant Spring (αCS) alleles, rs766432 in BCL11A, rs9399137 in HBS1L-MYB, and rs7482144-XmnI were evaluated. Modifiers were compared between 102 community- and 104 hospital-recruited cases. Alleles of β+, -SEA, -α3.7, αCS, and a minor allele of rs9399137 were prevalent in the community and mild severity groups (p < 0.05). Multiple linear regression analysis associated modulating alleles with −4.299 (-SEA), −3.654 (β+), −3.065 (rs9399137, C/C), −2.888 (αCS), −2.623 (‐α3.7), −2.361 (rs7482144, A/A), −1.258 (rs9399137, C/T), and −1.174 (rs7482144, A/G) severity score reductions (p < 0.05). Certain modifiers must be considered in routine prenatal genetic counseling for Hb E/β-thalassemia.

Genetic heterogeneity of thalassemia major patients in Rembang Regency, Central Java, Indonesia

Link of Video Abstract: https://www.youtube.com/watch?v=RG95aJkUndg Background: Thalassemia and hemoglobinopathies are caused by mutations in the globin genes that reduce haemoglobin synthesis. In many Asian countries, including Indonesia, thalassemia is a common inherited disorder. Thalassemia has specific characteristics due to the wide variability of the mutations from various populations. Therefore, screening protocol should be designed on specific populations’ regional gene mutation patterns. This study aims to investigate the mutational diversity of the globin genes in thalassemia major patients in Rembang Regency, Central Java, Indonesia. Methods: Genetic mutations were carried out in all major thalassemia patients who were recorded and underwent routine blood transfusions at the Rembang District Hospital from 2018 – 2020. Mutation identification was carried out using a PCR- RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism) based method, the ACRS (Amplified Created Restriction Site) method, and genome sequencing. Results: The most common genotypes are double heterozygous HbE and Cd 35 mutation (-C) (42.87%), HbE and IVS1-nt.5 mutations (G&gt; C) (28.57%), HbE and IVS1- nt.2 mutations (T&gt; C), HbE and codon 8/9 (insertion + G), codon 8/9 (insertion + G) and Hb Malay, as well as Hb Adana and Hb Constant Spring (1.74%). Conclusion: The β-thalassemia and α-thalassemia mutations most commonly found in Rembang Regency are Cd 35 (-C) and non-deletional mutations.

An analysis of the distribution and spectrum of alpha thalassemia mutations in Rasht City, North of Iran.

Alpha thalassemia is one of the most common hereditary hemoglobin disorders worldwide, particularly in the Middle East, including Iran. Therefore, determining the spectrum and distribution of alpha thalassemia mutation is a fundamental component of preventive approaches and management strategies. The present study reviews the genetic testing and blood laboratory results of 455 candidates eligible for marriage who were suspected of being thalassemia carriers and on whom genetic testing was performed from 21 March 2013 to 31 December 2020 in Rasht City. A total of 114 (25.05%) alpha thalassemia cases were identified. Fifteen different alpha mutations were found. The most common mutation among the study population was -α3.7 deletion in 55 patients (48.24%), followed by Hb Constant Spring (C.S) in 21 patients (18.42%) and poly A2 in 16 (14.03%). Also, most of the patients were silent carriers. The deletion type of mutation was much more common than non-deletion mutations. Our study reveals genetic heterogeneity and alpha thalassemia diversity among the Rasht City population. We expect that these findings will help guide premarital screening and genetic counseling, prenatal diagnosis of thalassemia, preventive strategy development, as well as a compilation of the alpha thalassemia catalog in Guilan province.

Fetal Hemoglobin H Hydrops Fetalis: Another Three Case Reports

We report three cases of fetalis hydrops associated with nondeletional α-thalassemia. Two cases were caused by hemoglobin (Hb) H-Quong Sz disease, and one caused by homozygous Hb Constant Spring. Fetal hydrops occurred in the late second trimester in all three cases. Our study indicates that for pregnancies at risk for fetal nondeletional Hb H disease, strict ultrasound follow-up is particularly important. Even without techniques of intrauterine transfusion treatment, early prenatal diagnosis can enable parents to make timely decisions.

Applying Multiplex ligation-dependent probe amplification technique to identify α-thalassemia carriers

α-thalassemia disease is mostly caused by mutations in the HBA1 and HBA2 genes that lead to the deficiency in the α-globin chain, which builds up the haemoglobin molecule. Depending on the number of missing α chains, the clinical manifestations of the disease are at different levels. This disease is inherited in an autosomal recessive manner, hence identifying healthy individuals carrying mutations in the α-thalassemia gene is essential for prenatal and premarital genetic counselling to reduce the incidence in the community. Multiplex ligation-dependent probe amplification (MLPA) technique was used to determine 15 people who were suspected of carrying the α-thalassemia gene based on their complete blood count. This study identified that therewere 12/15 people carrying --SEA mutation, 1/15 carrier having -α3.7 mutation, 1/15 carrier having -α4.2 mutation and 1/15 person carrying point mutation Hb constant spring -αHbCs.

Clinical and Haematological Parameters of Commonly Reported Non-deletional α-thalassaemia Mutations in Southeast Asia: A Review

Alpha (α)-thalassaemia is a common genetic disorder worldwide caused by the deletion and rarely non-deletional mutations of the α-globin gene. Nearly 70 types of non-deletional mutations have been reported worldwide, and this review focuses on the common ones affecting α-thalassaemia patients. The common mutations are initiation codon mutation, codon 30, haemoglobin (Hb) Constant Spring, Hb Quang Sze, Hb Adana and Hb Evora. The haematological parameters of non-deletional mutations usually show mild changes. However, a severe reduction in haemoglobin level, mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), and mean corpuscular haemoglobin count (MCHC) has been observed among compound heterozygous HbH disease, involving both deletional and non-deletional mutations. Although non-deletional mutations are rarely reported, it requires the study of more cases to understand the clinical phenotypes that lead to severe clinical manifestations.

Combined Gap-Polymerase Chain Reaction and Targeted Next-Generation Sequencing Improve α- and β-Thalassemia Carrier Screening in Pregnant Women in Vietnam

Vietnam has a high thalassemia burden. We collected blood samples from 5880 pregnant Vietnamese women during prenatal health checks to assess thalassemia carrier frequency using combined gap-polymerase chain reaction (gap-PCR) and targeted next-generation sequencing (NGS). Thalassemia carriers were identified with prevalence of 13.13% (772), including 7.82% (460) carriers of α-thalassemia (α-thal), 5.31% (312) carriers of β-thalassemia (β-thal), and 0.63% (37) concurrent α-/β-thal carriers. Deletional mutations (368) accounted for 80.0% of α-thal carriers, of which, ––SEA (Southeast Asian) (n = 254; 55.0%) was most prevalent, followed by the –α3.7 (rightward) (n = 66; 14.0%) and –α4.2 (leftward) (n = 45; 9.8%) deletions. Hb Westmead (HBA2: c.369C>G) (n = 53) and Hb Constant Spring (Hb CS or HBA2: c.427T>C) (in 28) are the two most common nondeletional α-globin variants, accounting for 11.5 and 6.0% of α-thal carriers. We detected 11 different β-thal genotypes. Hb E (HBB: c.79G>A) (in 211) accounted for 67.6% of β-thal carriers. The most common β-thal genotypes were associated with mutations at codon 17 (A>T) (HBB: c.52A>T), codons 41/42 (–TTCT) (HBB: c.126_129delCTTT), and codon 71/72 (+A) (HBB: c.217_218insA) (prevalence 0.70%, 0.68%, and 0.2%, respectively). Based on mutation frequencies calculated in this study, estimates of 5021 babies in Vietnam are affected with clinically severe thalassemia annually. Our data suggest a higher thalassemia carrier frequency in Vietnam than previously reported. We established that combining NGS with gap-PCR creates an effective large-scale thalassemia screening method that can detect a broad range of mutations.

CRISPR/Cas9 (D10A) nickase-mediated Hb CS gene editing and genetically modified fibroblast identification

ABSTRACT This study investigated whether CRISPR/Cas9 (D10A) nickase-mediated gene editing can correct the aberrant Hb Constant Spring mutation (Hb CS or HBA2: c.427 T > C) in fibroblasts. Vectors for repairing the α-globin-encoding gene, HBA2:c.427 T > C mutation, includingthe CRISPR/Cas9(D10A)-sg plasmid and donor with homology arms, were constructed and used to perform gene editing in patient-derived fibroblasts. We subsequently analyzed the genetic correction, the gene editing efficiency and off-target effect. Sequencing analysis and the BamHI assay showed that HB CS mutant cells were repaired with Hb CS point mutations, the editing efficiency was 4.18%~9.34% and no off-target effects were detected. The results indicate that the HB CS mutant gene is effectively repaired by the CRISPR/Cas9 (D10A)system, which may enable truly personalized therapy for precise repair of α-thalassemia.

Diagnostic value of fetal hemoglobin Bart\u2019s for evaluation of fetal \u03b1-thalassemia syndromes: application to prenatal characterization of fetal anemia caused by undiagnosed \u03b1-hemoglobinopathy

BackgroundTo 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.MethodsA 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.ResultsAmong 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.ConclusionsThe 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.

Misleading HbA1c Measurement in Diabetic Patients with Hemoglobin Variants.

Background and Objectives: Hemoglobin A1c (HbA1c) is widely used for the monitoring and management of diabetes mellitus. The aim of this study is to investigate the influence of hemoglobin (Hb) variants on the measurement of HbA1c. Materials and Methods: HbA1c levels of 845 blood samples obtained from diabetic patients with various hemoglobin types were measured using a turbidimetric inhibition immunoassay and capillary electrophoresis. Results: Of 845 patients with diabetes, 65.7% (555/845) have the normal hemoglobin type (A2A) and 34.3% (290/845) have various abnormal hemoglobin types, including heterozygous HbE 30.2% (255/845), homozygous HbE 1.9 % (16/845), Hb Constant Spring (CS) trait 1.4% (12/845), CSEA Bart’s 0.2% (2/845), and beta-thalassemia trait 0.6% (5/845). In most of the patients with diabetes, HbA1c levels determined by two different methods, inhibition immunoassay and capillary electrophoresis, gave strong positive correlation (R = 0.901, P < 0.001), except for those with homozygous HbE (N = 16) and CSEA Bart’s (N = 2). In all 18 patients with homozygous HbE and CSEA Bart’s, the HbA1c was undetectable by capillary electrophoresis, meaning that their estimated average glucose was undeterminable, although their HbA1c levels could be measured using an inhibition immunoassay. The discrepancy of HbA1c results obtained from two different methods is noted in patients without HbA. Conclusions: We have demonstrated the erroneous nature of HbA1c measurement in patients with hemoglobin variants, especially in those without HbA expression. Therefore, in the population with a high prevalence of hemoglobinopathies, hemoglobin typing should be considered as basic information prior to HbA1c measurement.

Molecular Characterization of β- and α-Globin Gene Mutations in Individuals with Borderline Hb A2 Levels

Elevated Hb A2 level (≥4.0%) is considered to be reliable parameter to identify β-thalassemia (β-thal) carriers. However, some β-thal carriers have been misdiagnosed as their Hb A2 levels are below 4.0%. In addition, coinheritance of α-thalassemia (α-thal) and β-thal might affect Hb A2 levels. Therefore, the aim of this study was to investigate the mutations of β- and α-globin genes in individuals with borderline Hb A2 levels in Thailand. Three hundred samples from individuals with Hb A2 levels of 3.5–3.9% were collected for molecular diagnosis of β-globin gene mutations. In addition, the α0-thal, α+-thal, Hb Constant Spring (Hb CS, HBA2: c.427T>C), and Hb Paksé (HBA2: c.429A>T) diagnostics were also performed. Sixteen samples (5.33%) had β-globin gene mutations, and codon 41/42 (–TTCT) (HBB: c.126_129delCTTT) was the most prevalent mutation. Ninety-eight samples (32.67%) had α-globin gene mutations including four Hb H (β4)-Hb CS disease, two Hb H disease, 13 heterozygous α0-thal, 11 homozygous α+-thal, two α+-thal/Hb CS, one α+-thal/Hb Paksé, 61 heterozygous α+-thal, and four Hb CS. Furthermore, seven cases of β-thal carriers coinheriting α-thal were observed, and five of them carried Hb H disease. High prevalence of both α- and β-thal in subjects with borderline Hb A2 levels suggested that molecular diagnosis of α- and β-thal should be performed, especially in a high prevalence area of thalasssemia carriers, for accurate diagnosis and genetic counseling to prevent and control new severe thalassemia cases. Moreover, β-thal carriers who coinherited Hb H disease might have reduced Hb A2 levels, leading to a misdiagnosis of β-thal in analysis programs.

Association of Hb Shenyang [α26(B7)Ala→Glu, GCG>GAG, HBA2: c.80C>A (or HBA1)] with Several Types of α-Thalassemia in Thailand

Hb Shenyang [α26(B7)Ala→Glu, HBA2: c.80C>A (or HBA1)] is a rare α chain variant. Its genotype-phenotype relationship and origin have not been described in Thailand before. Three Thai subjects (P1–P3) carrying this variant were studied. Hemoglobin (Hb) analysis was performed by capillary electrophoresis (CE) and high performance liquid chromatography (HPLC) as well as molecular characterization using appropriate polymerase chain reaction (PCR) techniques and DNA sequencing. Hemoglobin analysis by HPLC revealed fast-moving abnormal peaks at a retention time (RT) of 1.59–1.62 min., while CE revealed a fast-moving abnormal Hb at zone 12 and ahead of Hb A2 in three subjects. DNA analysis revealed a C>A transition at codon 26 of the α2-globin gene glutamic acid to replace alanine, corresponding to Hb Shenyang. The Southeast Asian [– –SEA α-thalassemia-1 (α-thal-1)] deletion was also identified in P1 and his mother, while Hb Constant Spring (Hb CS, HBA2: c.427T > C) was identified in P2. The Hb Shenyang concentration measured by CE revealed 5.1–17.2% heterozygosity with normal red blood cell (RBC) parameters. The α haplotype [+ – S + – + –] [S signifies the inter ζ hypervariable region (HVR)] was associated with the Thai Hb Shenyang. The genotype-phenotype relationship indicates Hb Shenyang is likely a non pathological Hb variant that has neither dramatic clinical symptoms nor hematological anomalies. A simple multiplex allele-specific PCR for rapid diagnosis of Hb Shenyang has been developed.

Alpha thalassemia genotypes in Kuwait

BackgroundThe frequency of the alpha thalassemia trait is approximately 40% in the Kuwaiti population, but there has been no comprehensive study of the prevalent alleles. This is a report of patients who were referred for molecular diagnosis over a 20-year period.MethodsThis is a retrospective study of the α-globin genotypes obtained in the Hemoglobin Research Laboratory of the Department of Pediatrics, Kuwait University from 1994 to 2015. Genotyping was performed by a combination of PCR, allele-specific oligonucleotide hybridization and reverse dot blot hybridization (Vienna Lab Strip Assay).ResultsFour hundred samples were characterized and analyzed from individuals aged < 1 month to 80 years, with a median of 6 years from 283 unrelated families. Most (90.8%) were Kuwaiti nationals. The commonest genotype was homozygosity for the polyadenylation-1 mutation (αPA-1α/α PA-1α) in 33.3% of the samples, followed by heterozygosity (αα/α PA-1α) for the same mutation in 32.3%. PA-1 was therefore the most frequent allele (0.59). The frequency of the α0 (−-MED) allele was 0.017. Rare alleles that were found in very low frequencies included α0 (−-FIL) in a Filipino child, Hb Constant Spring, Hb Adana, and Hb Icaria.ConclusionThere is a wide variety of alpha thalassemia alleles among Kuwaitis, but nondeletional PA-1 is by far the most common cause of the moderate to severe HbH (β4 tetramer) disease phenotype. The α0 (−MED) allele is also encountered, which has implications for premarital counseling, especially for the possibility of having babies with alpha thalassemia major (Barts hydrops fetalis).