Abstract
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.
Keywords: α-thalassemia, β-thalassemia, Hb E-β-thalassemia, prenatal diagnosis, genetic interaction
Introduction
Hemoglobin (Hb) E-β0-thalassemia is the most common form of thalassemia found in northeast Thailand [1]. The disease exhibits variable clinical phenotype, ranging from mild non-transfusion dependent thalassemia (NTDT) to severe transfusion-dependent thalassemia (TDT) [2,3]. This marked phenotypic diversity is associated with a great variety of genotypes, including different β-thalassemia alleles, co-inheritance of α-thalassemia, and the presence of genetic determinants associated with increased production of γ-globin chains and consequent ability to produce functional fetal hemoglobin (Hb F) in adult life [4-7]. Among these genetic modifiers, co-inheritance of α0-thalassemia is a significant factor that can dramatically reduce the clinical severity of the cases in our population [8,9]. In Thailand, according to the national prevention and control program of thalassemia, Hb E-β0-thalassemia is one of the targeted severe thalassemia diseases [10]. Prenatal diagnosis is routinely offered to a couple at risk of having a fetus with the disease [1]. Therefore, identification of α0-thalassemia in an affected fetus is useful. Due to the variability of the phenotype associated with the disease, it is essential to examine the possible co-inheritance of genetic modifiers in the fetus, especially α0-thalassemia, before a decision is made appropriately. The micromapping survey in our area in northeast Thailand has identified the prevalence of 5.8% for α0-thalassemia, 0.9% for β-thalassemia, and 41.7% for Hb E [11]. A genetic co-inheritance of these thalassemia defects in the population is expected. Our previous studies in adult subjects showed that the prevalence of α0-thalassemia in β-thalassemia carrier, Hb E carriers, and homozygous Hb E were 4.4%, 10.4%, and 4.6%, respectively [12-14]. In this study, we examine the prevalence of co-inheritance of α0-thalassemia in a large retrospective cohort of affected fetuses with Hb E-β0-thalassemia encountered at our prenatal diagnosis service nine consecutive years during January 2011 to December 2019.
Material and methods
Subjects
Ethical approval of the study protocol was obtained from the Institutional Review Board (IRB) of Khon Kaen University, Khon Kaen, Thailand (HE622173). A retrospective review was made on 1,592 couples at risk of having fetuses with Hb E-β0-thalassemia referred to our Thalassemia Service Unit, Centre for Research and Development of Medical Diagnostic Laboratories (CMDL), Khon Kaen University, Khon Kaen, Thailand, for prenatal diagnosis during January 2011 to December 2019. Left-over DNA specimens were selectively recruited from 415 affected fetuses with Hb E-β0-thalassemia disease. These DNA specimens were prepared routinely from chorionic villi, amniotic fluid, or fetal blood specimens obtained at prenatal diagnosis [1].
DNA analysis
At our routine setting, identification of β-thalassemia and Hb E mutations are carried out using allele-specific PCR and related techniques [1]. Screening for α0-thalassemia mutation (SEA & THAI deletions) was done in the 415 affected fetuses using gap-PCR as previously described [15,16]. Alternatively, α0-thalassemia was detected simultaneously with the Hb E gene in a modified multiplex PCR manner, as shown in Figure 1 [17]. The multiplex PCR was carried out in a reaction volume of 50 µL containing 1 µg of fetal DNA in a PCR buffer (10 mM Tris-HCl pH 8.3, 50 mM KCl, 3 mM MgCl2, 0.001% gelatin), 200 mM dNTPs, 1.005 M Betaine, 2% Dimethyl sulfoxide, 1.5 pmol each of primer; γ4 (5’-GGCCTAAAACCACAGAGT-3’), γ5 (5’-CCAGAAGCGAGTGTGTGGAA-3’), S3 (5’-TCCCATAGACTCACCCTGAA-3’) and G24 (5’-CGTGGATGAAGTTGGTGGTA-3’), 2.4 pmol each of primer; αG64 (5’-CGATCTGGGCTCTGTGTTCT-3’) and αG65 (5’-TGGAGTGCAGTGTTGTAGTC-3’), and 2 units Taq DNA polymerase (Biotools, B&M Labs, Madrid, Spain). After initial heating at 95°C for 5 min, a PCR process (95°C for 1 min, 63°C for 1 min, and 72°C for 90 sec) was carried out on a SimpliAmp Thermal Cycler (Applied Biosystems, Waltham, MA, USA) for 30 cycles. The PCR amplicon was analyzed on 2% agarose gel electrophoresis and visualized under UV light after staining with ethidium bromide.
Figure 1.
Multiplex PCR for simultaneous identification of Hb E and α0-thalassemia (SEA deletion) genes. The locations and orientations of the primers used in the PCR assay are depicted. A: The Hb E allele-specific primer (G24) is used with a common primer (S3) to produce a 400 bp Hb E-specific fragment. Two common primers, γ4 and γ5 for Gγ-globin gene promoter, are used to generate a 578 bp internal control fragment. B: The primers αG64 and αG65 are used to produce a 225-bp specific fragment of α0-thalassemia (SEA deletion). C: A representative 2% agarose gel electrophoresis. M is λ/Hind III DNA markers. Lane 1 is normal, lanes 2, 5, and 6 are positive for the α0-thalassemia (SEA deletion), lanes 3 and 7 are positive for Hb E, and lane 4 is positive for both Hb E and α0-thalassemia (SEA deletion).
Statistical analysis
Frequency of α0-thalassemia was presented as number and percentage. Hematological values and Hb profiles among at-risk couples were described by mean and standard derivation. All descriptive statistics were performed using Minitab version 16 (Minitab, Inc., USA).
Results
Thalassemic diseases at-risk for the fetuses
From January 2011 to December 2019, a total of 3,699 at-risk couples were referred to our center for prenatal diagnosis of thalassemia. Of these, 1,592 couples were at risk of having fetuses with Hb E-β0-thalassemia disease based on initial Hb and DNA analyses. Some of them also carried additional risks for homozygous α0-thalassemia and homozygous β-thalassemia, as shown in Table 1. As shown in the Table, Hb analysis revealed, in most couples (1,544/1,592; 97.0%) with Hb A2A (Hb A2>3.5% for β-thalassemia trait) in one of the couples and EA (Hb E>25% for Hb E trait) in another, indicating a 25% risk of Hb E-β-thalassemia in the fetuses (Group 1). Based on the national screening protocol, prenatal testing of these at-risk couples in group 1 focuses mainly on β-thalassemia and Hb E, and analysis of α0-thalassemia is not performed. In the remaining couples, 45 (45/1592; 2.8%) had additional risks for homozygous α0-thalassemia since one of the couples carried β-thalassemia heterozygote, Hb E homozygote, or Hb E heterozygote (with Hb E<25%, possibly co-inheritance of α0-thalassemia requiring further PCR analysis of α0-thalassemia). Therefore, these 45 couples were at risk of having fetuses with both Hb E-β0-thalassemia and homozygous α0-thalassemia. Thus, the fetuses of these 45 couples were tested at prenatal diagnosis for β0-thalassemia, Hb E, and α0-thalassemia mutations. In contrast, the last three couples (3/1,592; 0.2%) were at risk for Hb E-β-thalassemia, homozygous α0-thalassemia and homozygous β-thalassemia. In this last group, one partner of the couples was a carrier of β-thalassemia, and their partner carried Hb E-β-thalassemia or homozygous Hb E disorders (Table 1).
Table 1.
Results of Hb analysis of 1,592 at-risk couples, classified into 6 different groups and the diseases at-risk for the fetuses
| Group | Results of Hb analysis | Diseases at-risk | No. | % | |
|---|---|---|---|---|---|
|
| |||||
| Husband/Wife | Husband/Wife | ||||
| 1 | A2A; Hb A2>3.5% | EA; Hb E>25% | a | 1,544 | 96.9 |
| 2 | A2A; Hb A2>3.5% | EA; Hb E≤25% | a, b | 29 | 1.8 |
| 3 | A2A; Hb A2>3.5% | EE | a, b | 9 | 0.6 |
| 4 | EF | EA; Hb E≤25% | a, b | 4 | 0.3 |
| 5 | EF | EE | a, b | 3 | 0.2 |
| 6 | A2A; Hb A2>3.5% | EF, EE/EF | a, b, c | 3 | 0.2 |
| Total | 1,592 | 100 | |||
A: Hb E-β0-thalassemia disease; b: Homozygous α0-thalassemia, and c: Homozygous β0-thalassemia.
β-thalassemia mutations and α0-thalassemia identified in affected fetuses
Retrospective reviews at prenatal diagnosis of these 1,592 at-risk couples showed that 415 (26.1%) fetuses were affected by Hb E-β0-thalassemia disease. A total of 18 different β-thalassemia mutations were identified. As expected, the two most common mutations were codons 41/42 (-TTCT) and codon17 (A-T), accounting for 48.0% and 27.7%, respectively. Other β-thalassemia mutations were encountered at much lower frequencies, as shown in Table 2. DNA samples of these 415 affected fetuses were further investigated for co-inheritance of α0-thalassemia (SEA & THAI deletions). With this analysis, we found 21 of 415 (5.1%) fetuses with Hb E-β0-thalassemia disease to carry α0-thalassemia (SEA deletion). Figure 2 summarizes a total number of affected fetuses with Hb E-β0-thalassemia disease and those with α0-thalassemia (SEA deletion) found each year during 2011-2019. Hematologic features and the result of DNA analysis of the parents of these 21 affected fetuses are presented in Table 3. As shown in the table, α0-thalassemia was identified in the parents with heterozygous β-thalassemia (n=13), heterozygous Hb E (n=7), homozygous Hb E (n=2), and Hb E-β-thalassemia (n=1). Except for a reduced level of Hb E in Hb E heterozygote with α0-thalassemia (Hb E<25%), we did not observe a difference in the hematologic features of these double heterozygotic subjects and those of heterozygotic subjects without α0-thalassemia in our archives. Therefore, screening of such thalassemia interactions in the parents based on hematological grounds may be difficult.
Table 2.
Number of affected fetuses with Hb E-β0-thalassemia according to β-thalassemia mutations in trans of Hb E mutation and number of fetuses with co-inheritance of α0-thalassemia
| β-thalassemia mutations | No | (%) | Number of fetuses with α0-thalassemia (SEA) (%) |
|---|---|---|---|
| CD 41/42 (-TTCT) | 199 | (48.0) | 11 (2.7) |
| CD 17 (A-T) | 115 | (27.7) | 7 (1.7) |
| IVSI-1 (G-T) | 26 | (6.3) | 2 (0.5) |
| IVSI-5 (G-C) | 19 | (4.6) | |
| CD 71/72 (+A) | 18 | (4.3) | |
| 3.4-kb deletion | 10 | (2.4) | |
| IVSII-654 (C-T) | 8 | (1.9) | |
| CD 35 (C-A) | 5 | (1.2) | |
| CD 41 (-C) | 3 | (0.7) | |
| CD 26 (C-T) | 2 | (0.5) | |
| CD 27 (+C) | 2 | (0.5) | 1 (0.2) |
| 105 bp del | 2 | (0.5) | |
| FIL del | 1 | (0.2) | |
| CD 43 (G-T) | 1 | (0.2) | |
| CD 30 (G-C) | 1 | (0.2) | |
| CD 15 (-T) | 1 | (0.2) | |
| CD 33/34 (+C) | 1 | (0.2) | |
| CD 95 (+A) | 1 | (0.2) | |
| Total | 415 | (100) | 21 (5.1) |
Figure 2.
Numbers of affected fetuses with Hb E-β0-thalassemia disease encountered within nine years from 2011 to 2019. The white bars indicate the total number of Hb E-β0-thalassemia affected fetuses and the gray boxes indicate the number of affected fetuses that co-inherited α0-thalassemia.
Table 3.
Hematologic values and Hb profiles of 21 at-risk couples who had affected fetuses with Hb E-β0-thalassemia and heterozygous α0-thalassemia (SEA), including results of α0-thalassemia analysis of the couples
| Group | Number of couples (%) | Hb analysis | α0-thal gene (SEA) | Rbc (x1012/L) | Hb (g/dL) | HCT (%) | MCV (fL) | MCH (pg) | RDW (%) | Hb A2/E (%) | Hb F (%) | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 10 (47.6) | Husband/Wife | A2A; Hb A2>3.5% | Pos | 5.4±1.0 | 11.6±1.8 | 35.7±5.1 | 66.1±4.9 | 21.1±1.6 | 15.4±2.1 | 5.8±0.8 | 1.3±0.5 |
| Husband/Wife | EA; Hb E>25% | Neg | 5.3±0.6 | 12.8±2.3 | 38.8±6.5 | 73.1±8.0 | 24.4±3.3 | 14.1±2.8 | 28.4±1.1 | 1.2±0.7 | ||
| 2 | 3 (14.3) | Husband/Wife | A2A; Hb A2>3.5% | Pos | 5.8±0.7 | 11.2±2.7 | 35.1±7.2 | 59.6±5.5 | 19.0±24 | 18.2±2.0 | 5.7±0.6 | 0.5±0.4 |
| Husband/Wife | EA; Hb E≤25% | Pos | 4.9±0.1 | 10.5±0.4 | 31.5±1.1 | 64.8±3.7 | 21.5±0.7 | 14.6±0.7 | 21.7±0.7 | 0.5±0.3 | ||
| 3 | 3 (14.3) | Husband/Wife | A2A; Hb A2>3.5% | Neg | 6.3±0.7 | 12.2±1.4 | 40.0±3.5 | 63.9±3.1 | 19.5±1.0 | 13.9±0.1 | 5.8±0.5 | 1.7±0.9 |
| Husband/Wife | EA; Hb E≤25% | Pos | 5.8±0.7 | 12.1±1.5 | 38.3±5.0 | 71.3±5.8 | 21.0±0.1 | 16.0±2.5 | 19.7±0.8 | 1.2±0.8 | ||
| 4 | 1 (4.8) | Husband | EE | Neg | 6.8 | 13.4 | 42.5 | 62.8 | 19.8 | 15.3 | 98.8 | 1.2 |
| Wife | A2A; Hb A2>3.5% | Pos | 5.3 | 11.0 | 34.9 | 65.9 | 20.8 | 16.9 | 5.7 | 0 | ||
| 5 | 1 (4.8) | Husband | A2A; Hb A2>3.5% | Neg | 4.6 | 10.9 | 30.4 | 66.5 | 23.9 | 13.8 | 5.2 | 0.5 |
| Wife | EE | Pos | 5.8 | 13.6 | 40.1 | 69.0 | 23.3 | 20.1 | 98.5 | 1.5 | ||
| 6 | 1 (4.8) | Husband | EE | na | 5.6 | 11.8 | 34.8 | 62.0 | 21.0 | 15.8 | 96.5 | 3.5 |
| Wife | A2A; Hb A2>3.5% | na | 5.3 | 11.4 | 36 | 67.0 | 21.3 | 14.8 | 5.2 | 1.1 | ||
| 7 | 1 (4.8) | Husband | EE | Pos | 6.3 | 13.2 | 37.9 | 60.1 | 20.9 | 18.6 | 90.2 | 1.9 |
| Wife | EF | Pos | 4.9 | 8.2 | 23.8 | 48.8 | 16.7 | 21.9 | 66.6 | 33.4 | ||
| 8 | 1 (4.8) | Husband | EF | Neg | 5.4 | 10.2 | 33.4 | 61.3 | 18.7 | 27.1 | 63.2 | 36.8 |
| Wife | EA; Hb E≤25% | Pos | 5.2 | 10.7 | 34 | 65.7 | 20.7 | 16.4 | 19.2 | 0.7 | ||
Values are presented as mean ± standard deviation or as raw data where appropriated. Pos: Positive; Neg: Negative; na: not available.
Simultaneous detection of α0-thalassemia and Hb E
Simultaneous identification of α0-thalassemia in the fetus with Hb E-β-thalassemia at prenatal diagnosis is the best alternative. This is shown representatively in Figure 3. Hematologic findings indicated that the father was a β0-thalassemia carrier (CD 41/42; -TTCT) associated with reduced MCV (66.1 fL) & MCH (21.6 pg), and elevated Hb A2 (5.7%). The mother was diagnosed as a Hb E carrier with 27.2% Hb E. The couple had a 25% risk of having a fetus with Hb E-β0-thalassemia disease. As shown in the figure, a multiplex PCR assay identified unexpectedly that the fetus was affected by Hb E-β0-thalassemia and α0-thalassemia, and the father was, in fact, a double β0-thalassemia/α0-thalassemia heterozygote.
Figure 3.
Prenatal diagnosis of Hb E-β0-thalassemia in a representative family. A: Pedigree analysis with hematological and Hb analysis results of the couples at risk. The arrow indicates the fetus whose amniotic fluid specimen (AF) was obtained at 16 weeks of gestation. A representative 2% agarose gel electrophoresis of the PCR products are shown. M is λ/Hind III DNA markers. B: The multiplex PCR assay for Hb E and α0-thalassemia (SEA deletion) showed that the father (Fa), the mother (Mo), and the fetus (AF) were respectively positive for α0-thalassemia, Hb E, and both Hb E and α0-thalassemia. C1 is a negative control. C: Allele-specific PCR assay for β0-thalassemia (CD 41/42; -TTCT). The result indicated that the father (Fa) and the fetus (AF) but not the mother (Mo) were positive for β0-thalassemia (CD 41/42; -TTCT). Therefore, the fetus was affected by Hb E-β0-thalassemia disease with a co-inherited α0-thalassemia (SEA deletion).
Discussion
Hb E-β0-thalassemia is a significant public health problem in Thailand and many Southeast Asian countries [1,14]. Generally, the patient requires regular blood transfusion for effective treatment, although variable phenotypic expression varying from mild to severe phenotype has been noted [3,19]. Several genetic factors have been identified as genetic modifiers of this disease. A study of Hb E-β0-thalassemia patients with non-transfusion-dependent thalassemia (NTDT) phenotype in northeast Thailand also showed many genetic factors, such as co-inheritance of α-thalassemia, Gγ-XmnI polymorphism, and other genetic determinants associated with increased production of γ-globin chains play important role in the severity of the disease [3,9,20,21]. Among these genetic modifiers, co-inheritance of α0-thalassemia was found to be a major genetic modifier for Hb E-β0-thalassemia disease. Our recent study in northeast Thailand demonstrated that Hb E-β0-thalassemia patients with co-inherited α0-thalassemia showed NTDT phenotype with a mean Hb level of 10.5±2.9 g/dL [21]. This is also the case in northern Thai patients where it was found that Hb E-β0-thalassemia patients with co-inherited α0-thalassemia showed a mild clinical phenotype with the mean Hb level of 7.9±1.5 g/dL, and growth was close to normal [22]. Therefore, identifying the co-inheritance of α0-thalassemia in the fetus with Hb E-β0-thalassemia disease is important additional information for phenotypic prediction of the expecting fetus and genetic counseling the parents. It is understandable that the affected fetus with this genetic thalassemia interaction would have a mild clinical phenotype. In this study, the prevalence of 5.1% (Table 2) co-inheritance of α0-thalassemia in fetuses with Hb E-β0-thalassemia disease indicates that this should not be overlooked at prenatal diagnosis in Thai population. A prevalence of 5.8% α0-thalassemia has been documented in the northeast Thai population [11]. Our previous study revealed that the prevalence of co-inherited α0-thalassemia in β-thalassemia heterozygote in our population is around 4.4% [12]. As shown in Table 3, among 21 couples who had fetuses with Hb E-β0-thalassemia disease with α0-thalassemia, only one of the couples carried α0-thalassemia. Accordingly, these couples do not carry the risk for fetal homozygous α0-thalassemia disease (Hb Bart’s hydrops fetalis) in their fetuses, information related to α0-thalassemia gets ignored, and no α0-thalassemia screening is carried out at prenatal diagnosis and counseling. Thus, two approaches may be carried out prospectively, i.e., massive screening of α0-thalassemia in all couples at risk for fetal Hb E-β0-thalassemia or selective identification of α0-thalassemia in all fetuses with Hb E-β0-thalassemia disease.
It is conceivable, as shown by Table 3 that based on hematological grounds, selective screening of α0-thalassemia in the couples with heterozygous β-thalassemia may be difficult. The hematologic features of the β-thalassemia heterozygote with or without α0-thalassemia are similar, especially since they both have hypochromic microcytosis and elevated Hb A2 i.e., still within a diagnostic range for a β-thalassemia heterozygote [12,23]. In contrast, for Hb E heterozygote, the reduced level of Hb E (plus Hb A2) (<25%) is a useful marker for recognition of a double heterozygosity for Hb E/α0-thalassemia [13]. In addition, as shown in Table 3, as compared to a plain Hb E trait (Hb E>25%), a double heterozygous Hb E/αo-thalassemia (Hb E<25%) had relatively lower MCV & MCH values [24]. According to the screening protocol, an individual with Hb E heterozygote and Hb E>25% is considered a plain Hb E carrier and no α0-thalassemia screening is essential [1,10]. For homozygous Hb E, it is helpful to do Hb analysis using capillary electrophoresis rather than Hb-HPLC to determine the level of Hb A2 since capillary electrophoresis, but not HPLC, can report the level of Hb A2 in the presence of Hb E. Selection of suspected cases with homozygous Hb E and α0-thalassemia is possible. We have demonstrated that co-inheritance of α0-thalassemia elevates the Hb A2 level in homozygous Hb E (>4.5%) [25]. These characteristics are helpful in selective screening of α0-thalassemia in couples with β-thalassemia heterozygote or Hb E-related disorders. However, this selective screening in couples can add to workload, and be labor-intensive, and expensive due to a high number of pregnancies each year.
Alternatively, screening of α0-thalassemia can be effectively performed in all fetuses with Hb E-β-thalassemia using a multiplex PCR assay to detect Hb E and α0-thalassemia as shown in Figure 3. In this approach, the fetus is screened for α0-thalassemia simultaneously with Hb E. Co-inheritance of α0-thalassemia with the Hb E-β-thalassemia disease in the fetus is readily identified, no matter on the status of α0-thalassemia of the parents. Complete thalassemia genetic interaction in the fetus can then be provided to the parents at genetic counseling before making an appropriate decision. It is also noteworthy that another approach is to perform a prenatal diagnosis using a fetal blood specimen and Hb fractionation using capillary electrophoresis. This Hb analysis system can demonstrate and quantitate Hb Bart’s (γ4) because of a co-inheritance of α0-thalassemia. Hb Bart’s is a homotetramer of excess γ-globin chain, presented in a fetus and newborn with α-thalassemia. It is a useful marker in cord blood for screening of α-thalassemia in newborns [26-28]. We have demonstrated previously that heterozygous α0-thalassemia fetuses produced Hb Bart’s around 5.0% when examined using capillary electrophoresis [29]. The fetus with Hb E-β0-thalassemia and α0-thalassemia would demonstrate this amount of Hb Bart’s in addition to Hb F and Hb E without Hb A.
In conclusion, this study in Thailand confirmed that as many as 5.1% of affected fetuses with Hb E-β 0-thalassemia disease carried α0-thalassemia (SEA deletion). These affected fetuses should have a mild clinical phenotype, and their parents should receive this complete genetic information at genetic counseling before making an appropriate decision. Therefore, we recommend screening of α0-thalassemia in all fetuses with Hb E-β0-thalassemia disease at routine prenatal diagnosis in the region to obtain the correct genotype of the affected fetuses, which is necessary for genetic counseling.
Acknowledgements
We thank Drs. Thawalwong Ratanasiri, Ratana Komwilaisakde, and Piyamas Saksiriwuttho of the Department of Obstetrics and Gynecology, Faculty of Medicine, Khon Kaen University for collection of fetal specimens. This study was supported by Khon Kaen University, Khon Kaen, Thailand. SF is a recipient of the Thailand Research Fund (TRF) Research Team Promotion Grant (RTA) of the Thailand Science Research and Innovation (TSRI), Thailand (Contract ID RTA6280005).
Disclosure of conflict of interest
None.
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