Clinical Perspective on Use of Long-Read Sequencing in Prenatal Diagnosis of Thalassemia

This is an editorial focusing on the clinical perspective of a long-read sequencing method in the prenatal diagnosis of alpha- and beta-thalassemia, including a comparison between this method and standard PCR-based methods. Though incremental, the increased sensitivity and specificity using long-read sequencing is an important advantage of this methodology in the prenatal diagnostic arena due to false positive or false negative results having greater consequence when a family is making decisions about their pregnancy.

The effect of different types of anemia on HbA1c levels in non-diabetics

BACKGROUND

Diabetes mellitus is one of the most common diseases worldwide with significant morbidity and mortality. HbA1c remains one of the most important methods for diagnosis and monitoring of the disease. Since HbA1c is a reflection of the glucose attached to red blood cells, factors affecting hemoglobin and red blood cells' half-life can influence HbA1c measurements.

OBJECTIVE

This study aims to evaluate the effect of different types of anemia including iron deficiency anemia, sickle cell anemia, β -thalassemia trait, and megaloblastic anemia on HbA1c levels in a tertiary hospital over the past 6 years (2016-2022).

METHOD

This is a retrospective chart review study of 324 patients including those with one of the four types of anemia mentioned above and a control group. The control group were healthy adults with normal HbA1c and hemoglobin, who were not known to have diabetes or anemia. Patients with diabetes or prediabetes based on self-reporting or elevated fasting, random blood sugar, or 2 hours post-prandial blood glucose were excluded.

RESULTS

The mean HbA1c levels were significantly higher in sickle cell anemia at 5.83% (95% CI = 5.39-6.28) and in iron deficiency anemia at 5.75% (95% CI = 5.68-5.82) when compared to the control group at 5.32% (95% CI = 5.22-5.41). However, the mean HbA1c levels in megaloblastic anemia were 5.38% (95% CI = 5.26-5.5) and 5.45% (95% CI = 5.21-5.69) in beta thalassemia trait, which were not significantly different when compared to the control group. HbA1c significantly decreased from 5.75 to 5.44% after treatment in the iron-deficient group with a p-value of < 0.001. Moreover, lower hemoglobin and higher red cell distribution width correlated with higher HbA1c levels in patients with sickle cell anemia.

CONCLUSION

This study found a significant increase in HbA1c levels in iron deficiency anemia and sickle cell disease in patients not known to have diabetes. However, there was no significant effect in those patients with β-thalassemia trait and megaloblastic anemia. Treatment of iron deficiency anemia significantly decreased the HbA1c level, bringing it back to normal.

Pregnancy outcomes among women affected with thalassemia traits

OBJECTIVE

To compare the maternal and perinatal outcomes between a group of pregnant women diagnosed with thalassemia traits and normal controls.

STUDY DESIGN

A retrospective cohort study was conducted on singleton pregnant women affected and unaffected by thalassemia traits who attended an antenatal care clinic and delivered in Siriraj Hospital. Thalassemia status for all subjects was diagnosed by hemoglobin typing and/or DNA analysis. Patient charts were reviewed from January 2007 to December 2018. The control participants were randomly selected from the same period, with a control-case ratio of around 1:1.

RESULTS

Overall, 1288 women with thalassemia traits (348 with α thal-1 trait, 424 with β thal trait and 516 with HbE trait) and 1305 women in the control group were recruited. Baseline characteristics of both groups were similar, with the exception that the hematocrit level in the first trimester in the thalassemia trait group was significantly lower than that in the control group (34.8 ± 3.4% VS 36.9 ± 3.0%; p < 0.001). The prevalence of pregnancy-induced hypertension (PIH) was higher in the thalassemia trait group, at 6.9% VS 4.7% in the control group; p = 0.018. When subgroups were analyzed between each thalassemia trait, the number of maternal anemias in the first and third trimester was higher for all thalassemia traits compared to the normal group. The β thal and HbE traits increased the risk of PIH, with a relative risk (RR) = 1.67 and 1.66, respectively.

CONCLUSIONS

Thalassemia traits minimally but significantly increase the risk of hypertensive disorders and maternal anemia. In addition, physiological changes during pregnancy may worsen the severity of anemia in the pregnant women with thalassemia traits.

Feasibility of combining short tandem repeats (STRs) haplotyping with preimplantation genetic diagnosis (PGD) in screening for beta thalassemia

β-thalassemia is an autosomal recessive disease with the reduction or absence in the production of β-globin chain in the hemoglobin, which is caused by mutations in the Hemoglobin subunit beta (HBB) gene. In Vietnam, the number of β-thalassemia carriers range from 1.5 to 25.0%, depending on ethnic and geographical areas, which is much higher than WHO's data worldwide (1.5%). Hence, preimplantation genetic diagnosis (PGD) plays a crucial role in reducing the rate of β-thalassemia affected patients/carriers. In this research, we report the feasibility and reliability of conducting PGD in combination with the use of short tandem repeat (STR) markers in facilitating the birth of healthy children. Six STRs, which were reported to closely linked with the HBB gene, were used on 15 couples of β-thalassemia carriers. With 231 embryos, 168 blastocysts were formed (formation rate of 72.73%), and 88 were biopsied and examined with STRs haplotyping and pedigree analysis. Thus, the results were verified by Sanger sequencing, as a definitive diagnosis. Consequently, 11 over 15 couples have achieved pregnancy of healthy or at least asymptomatic offspring. Only three couples failed to detect any signs of pregnancy such as increased Human Chorionic Gonadotropin (HCG) level, foetal sac, or heart; and one couple has not reached embryo transfer as they were proposed to continue with HLA-matching to screen for a potential umbilical cord blood donor sibling. Thus, these results have indicated that the combination of PGD with STRs analysis confirmed by Sanger sequencing has demonstrated to be a well-grounded and practical clinical strategy to improve the detection of β-thalassemia in the pregnancies of couples at-risk before embryo transfer, thus reducing β-thalassemia rate in the population.

[Application value of high-throughput sequencing for the detection of thalassemia in ethnic Li minority areas]

OBJECTIVE

To assess the value of high-throughput sequencing for the detection of thalassemia-associated variants in ethnic Li minority areas of Hainan, China.

METHODS

In Baoting Li and Miao Autonomous County of Hainan Province, 1842 middle school students were randomly selected as the subjects, which included 1249 ethnic Lis, 454 ethnic Hans, and 139 individuals from other ethnic minorities. With DNA extracted from peripheral blood samples, gap-PCR combined with high-throughput sequencing were carried out to detect potential variants of the globin genes.

RESULTS

In total 22 α-thalassemia genotypes, 5β-thalassemia genotypes, and 21 α-composite β-thalassemia genotypes were detected. The carrier rates for ethnic Li, ethnic Han and other ethnic minorities were 78.14%, 24.01%, and 28.06%, respectively. In addition, 22 fusion genes, 8 variants leading to abnormal hemoglobin, and 10 rare mutations were identified.

CONCLUSION

High-throughput sequencing can detect a wide range of genetic variants associated with thalassemia in the ethnic Li minority areas and has played an important role for the identification of fusion genes, variants underlying hemoglobin anomalies and rare mutations.

Using FIB-4 score as a screening tool in the assessment of significant liver fibrosis (F2) in patients with transfusion-dependent beta thalassaemia: a cross-sectional study

OBJECTIVE

To evaluate the performance of the fibrosis-4 (FIB-4) score as a screening tool to detect significant liver fibrosis (F2) compared with transient elastography (TE), among chronic transfusion-dependent beta-thalassaemia (TDT) patients in a resource-poor setting.

DESIGN

A cross-sectional study.

SETTING

Adolescent and Adult Thalassaemia Care Centre (University Medical Unit), Kiribathgoda, Sri Lanka.

PARTICIPANTS

45 TDT patients who had undergone more than 100 blood transfusions with elevated serum ferritin >2000 ng/mL were selected for the study. Patients who were serologically positive for hepatitis C antibodies were excluded.

OUTCOME MEASURES

TE and FIB-4 scores were estimated at the time of recruitment in all participants. Predefined cut-off values for F2, extracted from previous TE and FIB-4 scores studies, were compared. A new cut-off value for the FIB-4 score was estimated using receiver operating characteristics curve analysis to improve the sensitivity for F2 prediction.

RESULTS

Of the selected 45 TDT patients, 22 (49%) were males. FIB-4 score showed a significant linear correlation with TE (r=0.52;p<0.0003). The FIB-4 score was improbable to lead to a false classification of TDT patients to have F2 when the FIB-4 cut-off value was 1.3. On the other hand, it had a very low diagnostic yield in missing almost all (except one) of those who had F2. Using a much-lowered cut-off point of 0.32 for FIB-4, we improved the pick-up rate of F2 to 72%.

CONCLUSIONS

Regardless of the cut-off point, the FIB-4 score cannot be used as a good screening tool to pick up F2 in patients with TDT, irrespective of their splenectomy status. On the contrary, at a 1.3 cut-off value, though FIB-4 is a very poor detector for F2 fibrosis, it will not erroneously diagnose F2 fibrosis in those who do not have it.

[Application of high-throughput sequencing technology in prenatal thalassemia screening in Zhuhai region]

OBJECTIVE

To compare the performance of high-throughput sequencing technology in prenatal thalassemia screening in Zhuhai area through comparison with traditional methods.

METHODS

A total of 1463 pregnant women were randomly selected. Following DNA extraction, high-throughput sequencing and conventional three-step thalassemia screening were carried out for each sample. Inconsistent results samples were validated by quantitative fluorescence PCR (QF-PCR) or Sanger sequencing. The results by the two methods were compared.

RESULTS

Among the 1463 cases, 318 (21.74%) were detected by conventional method, which included 210 (14.35%) with α-thalassemia, 97 (6.63%) with β-thalassemia, 11 (0.75%) with composite α- and β-thalassemia. Meanwhile, 379 cases (25.91%) of thalassemia were detected by high-throughput sequencing, which included 260 (17.77%) with α-thalassemia, 107 (7.31%) with β-thalassemia, 12 (0.82%) with composite α- and β-thalassemia. Six one cases were missed by the conventional method, which yielded a missed diagnosis rate of 16.09%, including 50 cases of α- thalassemia,10 cases of β-thalassemia, and 1 case of α-compound β-thalassemia. No cases of thalassemia were missed by high-throughput sequencing, and 10 rare thalassemia genotypes were detected.

CONCLUSION

High-throughput sequencing technology can improve the detection rate of thalassemia and reduce the missed diagnosis rate. It has a high application value in prenatal thalassemia screening in Zhuhai area and can more effectively prevent the birth of patients with severe thalassemia.

[Molecular Epidemiological Characteristics and Differential Diagnosis of Common δβ-Thalassemia/HPFH]

OBJECTIVE

To investigate the molecular epidemiological characteristics of common δβ-thalassemia/hereditary persistence of fetal hemoglobin(HPFH) in the prepregnant population in Huadu, and to provide a laboratory basis for prevention and control of thalassemia.

METHODS

Blood samples of childbearing age people in Huadu District of Guangzhou who participated in free thalassemia testing from January 2016 to July 2021 were collected for hematological parameters analysis and hemoglobin electrophoresis. Chinese ^Gγ⁺(^Aγδβ)⁰-thalassemia, ^SEA-HPFH and Taiwanese deletion β-thalassemia were detected by Gap-PCR in the samples with higher HbF(≥5%). Primers were designed for the proximal HBG1 and HBG2 promoter, and the point mutations in the proximal promoter region were detected by Sanger sequencing. Hematology parameters data were statistically analyzed.

RESULTS

Among 27 088 samples, Thirteen cases of Chinese ^Gγ⁺(^Aγδβ)⁰-thalassemia and thirty-three cases of ^SEA-HPFH were detected, which including 3 cases of Chinese ^Gγ⁺(^Aγδβ)⁰/β^N compounded with --^SEA/αα and three cases of ^SEA-HPFH/β^N compounded with --^SEA/αα. 6 carriers with ^Aγ-196 C>T were also detected; No Taiwanese thalassemia genetype was detected. The total detection rate of common δβ-thalassemia/HPFH was 0.19% (52/27 088). There were significant differences in the levels of MCV, MCH, HbA₂, and HbF among Chinese ^Gγ⁺(^Aγδβ)⁰-thalassemia, ^SEA-HPFH, ^Aγ-196 C>T (P<0.001). The hematological parameters of ^Aγ-196C>T combined with α⁰-thalassemia were similar to those of Chinese ^Gγ⁺(^Aγδβ)⁰-thalassemia carriers, and only HbA₂ was significantly lower than that of the latter, which was helpful for clinical identification.

CONCLUSION

δβ-thalassemia/HPFH should be included in the scope of thalassemia prevention program in the prepregnant population in Huadu District, and hematological parameters can provide some basis for identifying different types of δβ-thalassemia/HPFH.

[Genotypic and hematological characteristics of 83 β-thalassemia mutation carriers and patients from Henan Province]

OBJECTIVE

To investigate the genotypic and hematological characteristics of β-thalassemia patients and carriers from Henan Province of China.

METHODS

Clinical data of the patients and carriers were collected. Results of routine blood test, hemoglobin electrophoresis and genetic testing were retrospectively analyzed.

RESULTS

Of the 83 β-thalassemia patients and carriers, there were 46 females and 37 males, and their mean age was 27.37 ± 14.71, ranging from 5 months to 83 years. A total of 13 types of β-thalassemia alleles (86 alleles in total) were detected, with the most common three including ISV-II-654(C>T) (33.72%), CD41-42(-TTCT) (26.74%) and CD17(A>T) (18.60%). Five rare alleles, including CD8-9(+G), IVS-II-1(G>A), CD42(T>G), and start codons ATG>AGG and ATG>ACG were identified. Among these, HBB: c.128T>G(CD42T>G) was previously unreported in China. Fifteen β-thalassemia genotypes were detected, which included 12 simple heterozygote genotypes (80 cases, 96.40%), 2 double heterozygote genotypes (2 cases, 2.40%) and 1 homozygote genotype (1 case, 1.20%). The main manifestations were mild microcytic hypochromic anemia and raised HbA2. Compared with those with a β⁺/β^N genotype, carriers with a β⁰/β^N genotype have lower mean corpuscular volume (MCV) and mean corpusular hemoglobin (MCH) but higher HbA2 (P<0.05).

CONCLUSION

β-thalassemia is not rare in Henan Province and its characteristics are different from those in high incidence areas, which deserves close attention. The newly discovered HBB: c.128T>G (CD42T>G) has enriched the spectrum of β-thalassemia mutations in China. Above results will also facilitate genetic counseling and prenatal diagnosis of β-thalassemia in Henan Province.

Molecular heterogeneity of β-thalassemia variants in the Eastern region of Morocco

Background

β‐thalassemia syndromes are the most common hereditary blood disorders in the world and are recognized as a major health problem in Morocco. They are characterized by the reduction or the absence of β‐globin chain synthesis. The severity of the disease depends on the nature of the variants affecting the β‐globin gene (HBB), and each ethnic group has its own mutation spectrum. Hereby, we present, for the first time, the molecular profile of β‐thalassemia in the Eastern region of Morocco.

Methods

This study concerns 39 cases from 33 families who were enrolled in the BRO Biobank. Nineteen were diagnosed with β‐thalassemia major and 20 with β‐thalassemia minor. To detect mutations of the β‐globin gene, we have used RFLP‐PCR and Sanger sequencing.

Results

Nine known β‐thalassemia variants have been identified. Among these, we reported, for the first time in the Moroccan population, the Czechoslovakian variant C38/39(‐C) at homozygous state. The C39(C > T) was the most frequent variant (72.54%), followed by FSC5(‐CT) (5.88%), FSC6(−A), IVS‐1‐110(G > A), −29(A > G), C38/39(‐C) (3.92% each), and finally by IVS‐I‐1(G > A), IVS‐II‐1(G > A), and −56(G > C) (1.96%). Of particular interest this mutational spectrum of β‐thalassemia is very different from that found in previous studies in Morocco or in other North African countries.

Conclusion

This study is the first contribution to the description of the molecular profile of β‐thalassemia in the Eastern region of Morocco. It shows the high molecular heterogeneity of β‐thalassemia in our country. Therefore, these results can be valuable for the implementation of carrier screening, genetic counseling, and prenatal diagnosis programs.

Mutations in Thalassemia Carrier Couples: The Importance of Prenatal Diagnostic Tests

BACKGROUND

Thalassemia carrier couples play an important role in increasing thalassemia patients. The study of thalassemia genotypes in carrier couples is also effective in improving genetic counseling for them. The aim of this study was to investigate the prevalence of thalassemia mutations and genotypes in couples.

METHODS

This cross-sectional study was performed on 241 couples who were suspected of thalassemia from April 2018 to March 2020 in Lorestan province. Statistical analysis of data was performed using SPSS software 16.0 (SPSS Inc., Chicago, IL, USA). Online tools such as www.ithanet.eu/db/ithagenes and http://globin.bx.psu.edu/ hbvar/menu.html were also used to match patients' mutations with known cases.

RESULTS

IVSII-1 (G>A), CD36-37 (-T), IVSI-110 (G>A), --Med, and α3.7 were the most common mutations in the beta and alpha genes, respectively. IVSII-1 (G>A) β0/β (26.1%), CD36-37 (-T) β0/β (21.1%), and IVSI-110 (G>A) β0/β (10.3%) genotypes were the most common in women. The frequency of these genotypes in men were 24.8%, 28.6%, and 12.8%, respectively. Among alpha thalassemia carriers, the α3.7α/α α genotype had the highest frequency among women (3.7%) and men (5.3%). Alpha and beta-thalassemia were 15 and 13 times higher in related women and 18 and 9 times higher in related men than non-related ones, respectively. This difference was statistically significant (p < 0.001). In addition, 12.8% of fetuses were thalassemia major, 31.9% beta thalassemia minor, and 10.3% normal.

CONCLUSIONS

Thalassemia screening in related couples plays an important role in reducing thalassemia major infants.

Using affected embryos to establish linkage phase in preimplantation genetic testing for thalassemia

BACKGROUND

This study aimed to evaluate the ability of next-generation sequencing (NGS) to conduct preimplantation genetic testing (PGT) for thalassemia using affected embryos.

METHODS

This study included data from 36 couples who underwent PGT for thalassemia without probands and relative pedigrees. NGS results were compared with prenatal diagnosis results.

RESULTS

Thirty-six couples (29 α-thalassemia and 7 β-thalassemia) underwent 41 PGT cycles (31 α-thalassemia and 10 β-thalassemia). Analysis using NGS produced conclusive results for all biopsied blastocysts (100%, 217/217). One hundred and sixty (73.7%, 160/217) were unaffected by thalassemia. Preimplantation genetic testing for aneuploidy revealed that 112 (70.0%, 112/160) were euploid. Single blastocysts were transferred into the uteri of 34 women (53 frozen embryo transfer [FET] cycles). Thirty-two cycles resulted in clinical pregnancies, with a clinical pregnancy rate of 60.1% (32/53) per FET cycle. Twenty-two cycles (22 couples) resulted in 23 live births, with a live birth rate of 43.4% (23/53; 3 cycles were ongoing pregnancies). All 25 embryos' prenatal diagnosis results and/or thalassemia gene analyses after delivery were concordant with the NGS-PGT results. Seven embryos (21.9%, 7/32) were miscarried before 12 weeks' gestation, and the abortion villus in four showed a normal karyotype and thalassemia results consistent with the NGS-PGT results. Aborted fetus samples from 3 cycles were not available because the pregnancy lasted less than 5 weeks.

CONCLUSION

NGS can be used to conduct PGT for thalassemia using affected embryos as a reference.

TRIAL REGISTRATION

Retrospectively registered.

Establishment of pregnant-specific intervals for hemoglobin (Hb) A2, HbF and cut-off points for HbA2 for thalassemia in Chongqing, China

OBJECTIVES

To analyze pregnant-specific intervals for hemoglobin A2 (HbA2), hemoglobin fetal (HbF), and cut-off points of HbA2 for thalassemia in Chongqing, China.

METHODS

Between September 2015 and April 2019, the study recruited 10039 individuals of reproductive age. Of which, 4399 healthy normal individuals were selected to determine reference values for HbA2 and HbF. The remaining 5640 individuals suspected of thalassemia were included to explore the cut-off points of HbA2 for thalassemia.

RESULTS

The reference values of HbA2 in males was 2.3-3.2%, in females was 2.1-3.1%, and in pregnant women was 1.9-3.1%. While the reference values of HbF in males was 0.0-0.0%, in females was 0.0-0.9%, and in pregnant women was 0.0-4.3%. Approximately 2.3% cut-off points for pregnant women was determined to be optimal for α-thalassemia screening. In the entire group, 2.5% was best for all α-thalassemia screenings. The cut-off for β-thalassemia screening using HbA2 was 3.2% for the entire group.

CONCLUSION

The reference interval of HbA2 for pregnant females group was significantly lower than other groups. Therefore, we recommend cut-off points of HbA2 for α-thalassemia at 2.3% for pregnant women. While partitioning was not needed due to gender. Gender and pregnancy had little effect on the cut-off points of HbA2 for β-thalassemia carrier.

Cascade screening for beta-thalassaemia in Pakistan: relatives' experiences of a decision support intervention in routine practice

Low uptake of cascade screening for βeta-thalassaemia major (β-TM) in the 'Punjab Thalassaemia Prevention Project' (PTPP) in Pakistan led to the development of a 'decision support intervention for relatives' (DeSIRe). This paper presents the experiences of relatives of children with β-TM of the DeSIRe following its use by PTPP field officers (FOs) in routine clinical practice. Fifty-four semi-structured qualitative interviews were conducted (April to June 2021) with relatives in seven cities in the Punjab province (Lahore, Sheikhupura, Nankana Sahab, Kasur, Gujranwala, Multan and Faisalabad). Thematic analysis shows that participants were satisfied with the content of the DeSIRe and its delivery by the FOs in a family meeting. They understood that the main purpose of the DeSIRe was to improve their knowledge of β-TM and its inheritance, and to enable them to make decisions about thalassaemia carrier testing, particularly before marriage. Participants also raised concerns about the stigma of testing positive; however, they believed the DeSIRe was an appropriate intervention, which supported relatives to make informed decisions. Our findings show that the DeSIRe is appropriate for use by healthcare professionals in routine practice in a low-middle income country, and has the potential to facilitate shared decision making about cascade screening for thalassaemia. Further research is needed to prove the efficacy of the DeSIRe.

[Clinical Diagnosis and Prenatal Screening of Hb Lepore-BW Associated with IVS-II-654 Heterozygous Mutation]

OBJECTIVE

To identify one case of rare Hb Lepore-BW associated with IVS-II-654 heterozygous mutation in Sichuan area.

METHODS

The blood routine examination and hemoglobin electrophoresis methods were used to analyze the blood routine parameters, HbA₂ and HbF in the samples of peripheral blood in proband and his parents, as well as the cord blood of pregnant woman. The detection of thalassemia gene and Sanger sequencing methods were used to detect the hemoglobin mutations.

RESULTS

The result showed that the Hb Lepore-BW heterozygous mutation was detected in the father of the proband, while a rare Hb Lepore-BW with IVS-II-654 heterozygous mutation was detected in the proband, as well as his mother and cord blood were both detected as IVS-II-654 heterozygous mutation.

CONCLUSION

The study identified a rare Hb Lepore-BW with IVS-II-654 heterozygous mutation, which was characterized by intermediate β-thalassemia. It is necessary to hemoglobin electrophoresis combined with routine blood testing in prenatal screening.

[Thalassemia Gene Detection Results and Application Value of Hematological Indexes Among Pregnant Women in Xindu District of Chengdu City]

OBJECTIVE

To analyze the genotype characteristics of α- and β-thalassemia and the diagnostic value of hematological indexes in pregnant women in Xindu District of Chengdu.

METHODS

The blood routine parameters(MCV) <80 fl and (or) (MCH) <27 pg and hemoglobin electrophoresis were used to screen the pregnant women, PCR-reverse dot blot hybridization(PCR-RDB) technique was used to detect the common α- and β-thalassemia gene types in the primary screening positive population. The husbands of the diagnosed pregnant women were recalled for gene testing, and the highly suspected patients were checked by gene sequencing.

RESULTS

Among the 7 049 pregnant women, 1 740(24.68%) cases were positive for primary screening. 180 patients were diagnosed as thalassemia gene positive, among them, 94 cases (52.22%) of α-thalassemia were detected and six genotypes were found, in which --^SEA /αα genotype was the highest (58 cases, 61.70%); 82 cases (45.56%) of β-thalassemia were detected and ten genotypes were found while CD41-42/N and CD17/N genotypes were the most common; there were 4 cases(2.22%) with α combined with β-thalassemia. Through clinical follow-up survey, there were 4 couples with the same type of thalassemia, one of them was induced labor after diagnosis of hemoglobin H disease. Receiver operating curve (ROC curve) was used to analyze the diagnostic value of hematological parameters in thalassemia positive pregnant women. The results showed that AUC(HBA₂)<AUC(MCHC)<AUC(RDW-SD)<AUC(MCH)<AUC(MCV) (P<0.01).

CONCLUSION

The most common genotypes of α- and β-thalassemia in pregnant women in Xindu District of Chengdu were --^SEA /αα, CD41-42/N, CD17/N. The blood routine indicators (HBA₂、RDW-SD、MCHC、MCH、MCV) have high diagnostic value for screening of thalassemia.

The prevalence and outcomes of α- and β-thalassemia among pregnant women in Hubei Province, Central China: An observational study

There is no information concerning the prevalence of thalassemia among pregnant women in Hubei Province currently. This study is aimed to explore the prevalence of α- and β-thalassemia genotypes among pregnant women in Hubei Province, and to explore the clinically applicable screening approach, as well as to investigate the pregnancy outcomes of α- and β-thalassemia carriers.Pregnant participants were recruited from 4 hospitals for the screening of α- and β-thalassemia mutations in Hubei Province. Polymerase Chain Reaction and flow cytometry methods were used to examine α- and β-thalassemia mutations. The hematological parameters and pregnancy outcomes of α- and β-thalassemia carriers were obtained from the hospital information system. The chi-square tests were used to evaluate the difference in hematological parameters between pregnant thalassemia carriers and the control group.Among 11,875 participants, 414 (3.49%) were confirmed with α-thalassemia carriers, 228 (1.92%) were confirmed with β-thalassemia carriers, and 3 (0.03%) were confirmed with both α- and β-thalassemia carriers. The frequency of -α3.7 accounted for 2.05% and it was the most frequent genotype of α-thalassemia; the proportion of IVS-II-654 was 0.85% and it was the most frequent genotype of β-thalassemia in Hubei Province. Furthermore, the proportion of patients with low mean corpuscular volume (MCV) or mean cell hemoglobin (MCH) values was accounted for 36.64% and 93.97% among α-thalassemia and β-thalassemia carriers, respectively. And participants with normal MCV and MCH values were accounted for 95.07% among non-thalassemia participants. High prevalence of pregnancy-induced diabetes (16.97%), preterm birth (9.96%), pregnancy-induced hypertension (8.12%), and low birth weight (5.90%) were observed among pregnant thalassemia carriers.MCV and MCH values were suggested to apply on the preliminary screening of pregnant β-thalassemia; however, it's unpractical on that of α-thalassemia. Furthermore, thalassemia carriers might have a high risk of negative pregnancy outcomes. These findings could be useful for the preliminary screening of thalassemia and perinatal care for the pregnant thalassemia carriers.

Alpha- and Beta-thalassemia: Rapid Evidence Review

Thalassemia is a group of autosomal recessive hemoglobinopathies affecting the production of normal alpha- or beta-globin chains that comprise hemoglobin. Ineffective production of alpha- or beta-globin chains may result in ineffective erythropoiesis, premature red blood cell destruction, and anemia. Chronic, severe anemia in patients with thalassemia may result in bone marrow expansion and extramedullary hematopoiesis. Thalassemia should be suspected in patients with microcytic anemia and normal or elevated ferritin levels. Hemoglobin electrophoresis may reveal common characteristics of different thalassemia subtypes, but genetic testing is required to confirm the diagnosis. Thalassemia is generally asymptomatic in trait and carrier states. Alpha-thalassemia major results in hydrops fetalis and is often fatal at birth. Beta-thalassemia major requires lifelong transfusions starting in early childhood (often before two years of age). Alpha- and beta-thalassemia intermedia have variable presentations based on gene mutation or deletion, with mild forms requiring only monitoring but more severe forms leading to symptomatic anemia and requiring transfusion. Treatment of thalassemia includes transfusions, iron chelation therapy to correct iron overload (from hemolytic anemia, intestinal iron absorption, and repeated transfusions), hydroxyurea, hematopoietic stem cell transplantation, and luspatercept. Thalassemia complications arise from bone marrow expansion, extramedullary hematopoiesis, and iron deposition in peripheral tissues. These complications include morbidities affecting the skeletal system, endocrine organs, heart, and liver. Life expectancy of those with thalassemia has improved dramatically over the past 50 years with increased availability of blood transfusions and iron chelation therapy, and improved iron overload monitoring. Genetic counseling and screening in high-risk populations can assist in reducing the prevalence of thalassemia.

Expression, functional mechanism and therapy application of long noncoding RNA in thalassemia

β-thalassemia (β-thal) is one of the most common genetic diseases in the world, its pathogenesis is extremely complex and there is no effective treatment at present. The birth of children with moderate and severe β-thal brings economic pressure to families, social medical and health services. Long noncoding RNA (lncRNA) is a type of noncoding protein transcripts with a length greater than 200 nucleotides, which is involved in a variety of biological processes, such as cell proliferation, differentiation and chromosome variation and plays an important role in the epigenetic and post-transcriptional regulation of genes. It has potential value in the diagnosis, prevention and treatment of β-thal. LncRNA possesses the characteristics such as tissue specificity, cell specificity, developmental stage specificity, space-time specificity and disease specificity, and its complex interaction network has become a challenge to translate research results into clinical practice. Taking lncRNA as an entry point, in-depth understanding of the function of lncRNA in β-thal and explanation of its related regulatory mechanisms will provide theoretical basis for targeting treatment of β-thal, which can improve the diagnosis and treatment of β-thal.

[Genetic Analysis and Prenatal Diagnosis of Thalassemia in Couples of Childbearing Age in Quanzhou Region Fujian Province, China]

OBJECTIVE

To explore the genotypes and prenatal diagnosis of thalassemia in couples of childbearing age in Quanzhou, Fujian Province.

METHODS

Blood routine and hemoglobin electrophoresis were performed for initial thalassemia screening in 76 328 couples in Quanzhou region from July 2017 to July 2020. The couples with positive initial screening results further underwent thalassemia gene test. Couples carrying homotypic thalassemia genes underwent prenatal diagnosis in the second trimester.

RESULTS

Among 76 328 couples of childbearing age, 1 809 couples of positive initial thalassemia screening were identified, with the positive rate about 2.37%. Further results of genetic detection of the 1 809 couples showed that 985 cases were diagnosed as α- thalassemia, of which --^sea/αα was the most frequency, followed by -α^3.7/αα and αα^QS/αα; 296 cases were diagnosed as β-thalassemia, the most frequency mutations were 654M/N and 41-42M/N; 26 cases of compound α and β-thalassemia were detected. In addition, 3 rare cases of thalassemia were detected, including --^THAI/αα, SEA-HPFH, and -α^6.9/--^sea. Among them, 108 couples were confirmed as homologous thalassemia, with the detection rate about 5.97%, including 96 couples of homologous α-thalassemia, 9 couples of homologous β-thalassemia, and 3 couples with one had compound α- and β-thalassemia. Among them, 17 couples with homologous α-thalassemia underwent prenatal diagnosis in the second trimester, of which 1 case of Hb Bart's Hydrops Syndrome, 3 cases of HbH disease, 9 cases of silent thalassemia or α-thalassemia minor, and 4 cases of healthy fetuses were detected. Fetal chromosome karyotype analysis showed that 16 cases were normal and 1 case diagnosed as Down syndrome.

CONCLUSION

Thalassemia screening in pre-marital and pre-pregnancy, and prenatal diagnosis can effectively reduce the birth of children with thalassemia intermediate and thalassemia major. It is necessary to perform chromosome karyotype analysis at the same time as prenatal diagnosis of thalassemia gene in order to avoid fetus with abnormal chromosome.

[The value of combined detection of HbA2 and HbF for the screening of thalassemia among individuals of childbearing ages]

OBJECTIVE

To assess the application value of combined detection of HbA2 and HbF for the screening of thalassemia among a population of childbearing age in Quanzhou, Fujian, and determine the optimal cut-off values for the region.

METHODS

Capillary hemoglobin electrophoresis and genetic testing for α and β globin gene mutations were simultaneously carried out on 11 428 patients with suspected thalassemia. Statistical methods were used to analyze the distribution of various types of thalassemia and compare the performance of HbA2 and HbF measurement for the screening of various types of thalassemia. The optimal cut-off values for HbA2 and HbF were determined with the ROC curves.

RESULTS

4591 patients with α, β, and αβ compound thalassemia were identified by genetic testing. The most common genotypes for α and β thalassemia included --SEA/αα and β654/βN, β41-42/βN, and β17/βN. The ROC curves were drawn to compare the performance of HbA2 screening for α-, β-, αβ-compound, static α-, mild α-, and intermediate α-thalassemia, and the maximum area under the curves was 0.674, 0.984, 0.936, 0.499, 0.731, 0.956, and the optimal cut-off values for HbA2 were 2.45%, 3.25%, 3.65%, 2.95%, 2.55%, 1.75%, respectively.

CONCLUSION

HbA2 is an efficient indicator for identifying intermediate types of α-, β-, and αβ compound thalassemia. The combination of HbA2 and HbF measurement can effectively detect carriers for β-thalassemia mutations.

Case Report: Abnormally Low Glycosylated Hemoglobin A1c Caused by Clinically Silent Rare β-Thalassemia in a Tujia Chinese Woman

BACKGROUND

Glycosylated hemoglobin A1c (HbA1c) is an important means of monitoring blood glucose and diagnosing diabetes. High-performance liquid chromatography (HPLC) is the most widely used method to detect HbA1c in clinical practice. However, the results of HbA1c by HPLC are susceptible to hemoglobinopathy. Here, we report a case of discordantly low HbA1c with an abnormal chromatogram caused by rare β-thalassemia.

CASE DESCRIPTION

A 36-year-old Tujia Chinese woman presented with an abnormally low HbA1c level of 3.4% by HPLC in a health check-up. The chromatogram of HbA1c showed an abnormal peak. Fasting blood glucose, routine blood tests and serum bilirubin were normal. Her body mass index was 27.86 kg/m². Hemoglobin electrophoresis showed low hemoglobin A and abnormal hemoglobin β-chain variants. The thalassemia gene test suggested a rare type of β-thalassemia (gene sequencing HBB: c.170G>A, Hb J-Bangkok (GGC->GAC at codon 56) in a beta heterozygous mutation). Glycated albumin (GA) was slightly increased. Oral glucose tolerance tests (OGTT) and insulin release tests indicated impaired glucose tolerance and insulin resistance. The hematologist advised follow-up visits. The endocrinologist recommended that the patient adopt lifestyle intervention. Three months later, GA returned to normal, and impaired glucose tolerance and insulin resistance improved.

CONCLUSIONS

Clinically silent β-thalassemia may lead to low HbA1c values and abnormal chromatograms by HPLC. In these circumstances, differential diagnosis is important. Checking the chromatogram may be helpful in interpreting HbA1c as well as identifying hemoglobinopathy. Further tests, such as GA, OGTT, hemoglobin electrophoresis and genetic tests, are needed for differential diagnosis.

Optimal strategies for carrier screening and prenatal diagnosis of α- and β-thalassemia

The thalassemias are inherited quantitative disorders of hemoglobin synthesis with a significant worldwide burden, which result in a wide spectrum of disease from the most severe transfusion-dependent form to the mildest asymptomatic carrier state. In this article, we discuss the importance of carrier, prenatal, and newborn screening for thalassemia. We examine the rationale for who should be screened and when, as well as the current methodology for screening. Deficiencies in the newborn screening program are highlighted as well. With the advent of inexpensive and rapid genetic testing, this may be the most practical method of screening in the future, and we review the implications of population-based implementation of this strategy. Finally, a case-based overview of the approach for individuals with the trait as well as prospective parents who have a potential fetal risk of the disease is outlined.

Non-Invasive Prenatal Test for β-Thalassemia and Sickle Cell Disease Using Probe Capture Enrichment and Next-Generation Sequencing of DNA in Maternal Plasma

BACKGROUND

Noninvasive prenatal testing (NIPT) of chromosomal aneuploidies based on next-generation sequencing (NGS) analysis of fetal DNA in maternal plasma is well established, but testing for autosomal recessive disorders remains challenging. NGS libraries prepared by probe capture facilitate the analysis of the short DNA fragments plasma. This system has been applied to the β-hemoglobinopathies to reduce the risk to the fetus.

METHOD

Our probe panel captures >4 kb of the HBB region and 435 single-nucleotide polymorphisms (SNPs) used to estimate fetal fraction. Contrived mixtures of DNA samples, plasma, and whole blood samples from 7 pregnant women with β-thalassemia or sickle cell anemia mutations and samples from the father, sibling, and baby or chorionic villus were analyzed. The fetal genotypes, including point mutations and deletions, were inferred by comparing the observed and expected plasma sequence read ratios, based on fetal fraction, at the mutation site and linked SNPs. Accuracy was increased by removing PCR duplicates and by in silico size selection of plasma sequence reads. A probability was assigned to each of the potential fetal genotypes using a statistical model for the experimental variation, and thresholds were established for assigning clinical status.

RESULTS

Using in silico size selection of plasma sequence files, the predicted clinical fetal genotype assignments were correct in 9 of 10 plasma libraries with maternal point mutations, with 1 inconclusive result. For 2 additional plasmas with deletions, the most probable fetal genotype was correct. The β-globin haplotype determined from linked SNPs, when available, was used to infer the fetal genotype at the mutation site.

CONCLUSION

This probe capture NGS assay demonstrates the potential of NIPT for β-hemoglobinopathies.

Hemoglobin A2 and Heterogeneous Diagnostic Relevance Observed in Eight New Variants of the Delta Globin Gene

BACKGROUND

Hemoglobin A (Hb A) (α₂β₂) in the normal adult subject constitutes 96-98% of hemoglobin, and Hb F is normally less than 1%, while for hemoglobin A₂ (Hb A₂) (α₂δ₂), the normal reference values are between 2.0 and 3.3%. It is important to evaluate the presence of possible delta gene mutations in a population at high risk for globin gene defects in order to correctly diagnose the β-thalassemia carrier.

METHODS

The most used methods for the quantification of Hb A₂ are based on automated high performance liquid chromatography (HPLC) or capillary electrophoresis (CE). In particular Hb analyses were performed by HPLC on three dedicated devices. DNA analyses were performed according to local standard protocols.

RESULTS

Here, we described eight new δ-globin gene variants discovered and characterized in some laboratories in Northern Italy in recent years. These new variants were added to the many already known Hb A₂ variants that were found with an estimated frequency of about 1-2% during the screening tests in our laboratories.

CONCLUSIONS

The knowledge recognition of the delta variant on Hb analysis and accurate molecular characterization is crucial to provide an accurate definitive thalassemia diagnosis, particularly in young subjects who would like to ask for a prenatal diagnosis or preimplantation genetic diagnosis.