Prevalence and genotypes of alpha- and beta-thalassemia carriers in Hong Kong -- implications for population screening

Prevalence, mutation distribution, and economic burden of thalassemia in China: a systematic review and regional analysis

BACKGROUND

Thalassemia poses a significant public health and economic challenge in China. Comprehensive data on its epidemiology, mutation spectrum, and economic impact are critical for improving prevention and treatment.

METHODS

This systematic review, adhering to PRISMA guidelines, analyzed studiesP{lea published between 1987 and 2024 from PubMed, FMRS, and CNKI. Data from 29 eligible studies, covering 679,697 individuals across 17 regions, were standardized using next-generation sequencing benchmarks.

RESULTS

The national carrier rate was 8.95%, with -SEA and βCD41-42 mutations most prevalent, particularly in Hainan and Guangxi. Thalassemia contributes an annual economic burden of 9.19 billion RMB and approximately 3,590 stillbirths in the absence of prevention programs.

CONCLUSIONS

While regional screening has reduced incidence since 1987, the disease continues to strain China's healthcare system. These findings highlight the pressing need to expand national prevention programs to mitigate its health and economic impacts. Insights from this review are vital for shaping public health strategies in high-prevalence areas.

Application of third-generation sequencing technology in the genetic testing of thalassemia

Thalassemia is an autosomal recessive genetic disorder and a common form of Hemoglobinopathy. It is classified into α-thalassemia and β-thalassemia. This disease is mainly prevalent in tropical and subtropical regions, including southern China. Severe α-thalassemia and intermediate α-thalassemia are among the most common birth defects in southern China. Intermediate α-thalassemia, also known as Hb H disease, is characterized by moderate anemia. Severe α-thalassemia, also known as Hb Bart's Hydrops fetalis syndrome, is a fatal condition. Infants with severe β-thalassemia do not show symptoms at birth but develop severe anemia later, requiring expensive treatment. Most untreated patients with severe β-thalassemia die in early childhood. Screening for thalassemia carriers and genetic diagnosis in high-prevalence areas significantly reduce the incidence of severe thalassemia. This review aims to summarize the genetic diagnostic approaches for thalassemia. Conventional genetic testing methods can identify 95-98% of thalassemia carriers but may miss rare thalassemia genotypes. Third-Generation Sequencing offers significant advantages in complementing other genetic diagnostic approaches, providing a basis for genetic counseling and prenatal diagnosis.

CRISPR-Cpf1 system and its applications in animal genome editing

The clustered regularly interspaced short palindromic repeats (CRISPR) and their associated protein (Cas) system is a gene editing technology guided by RNA endonuclease. The CRISPR-Cas12a (also known as CRISPR-Cpf1) system is extensively utilized in genome editing research due to its accuracy and high efficiency. In this paper, we primarily focus on the application of CRISPR-Cpf1 technology in the construction of disease models and gene therapy. Firstly, the structure and mechanism of the CRISPR-Cas system are introduced. Secondly, the similarities and differences between CRISPR-Cpf1 and CRISPR-Cas9 technologies are compared. Thirdly, the main focus is on the application of the CRISPR-Cpf1 system in cell and animal genome editing. Finally, the challenges faced by CRISPR-Cpf1 technology and corresponding strategies are analyzed. Although CRISPR-Cpf1 technology has certain off-target effects, it can effectively and accurately edit cell and animal genomes, and has significant advantages in the preclinical research.

A specific early eluting peak in Bio-Rad Variant II cation-exchange high-performance liquid chromatography (CE-HPLC) for the screening of alpha-thalassaemia in a Chinese population

The early eluting peaks in the first minute of cation-exchange high-performance liquid chromatography (CE-HPLC) are often not analysed in haemoglobin pattern studies, except for haemoglobin (Hb) Bart's and Hb H peaks. In this study, we described the presence of a specific α-thalassaemia early eluting peak (αEEP) at the retention time of 0.24 min generated by Variant II CE-HPLC (β-Thalassaemia Short Program; Bio-Rad Laboratories). We have evaluated the utility of αEEP for the screening of α-thalassaemia trait in our local Chinese population in comparison to the Hb H inclusion body test. A total of 303 blood samples presenting with microcytosis were sent for haemoglobin pattern study and were analysed for the presence or absence of αEEP and Hb H inclusions. Twenty cases with a normal mean corpuscular volume were assessed as a control. Discordant results between the αEEP and the Hb H inclusion test were reviewed with the α-globin genotyping test performed. The concordance rate of the αEEP and the Hb H inclusion body test was 96.0% (κ=0.921, p<0.001). Eight of 303 cases (2.6%) were initially negative for the Hb H inclusion test but positive for the αEEP. All eight cases were found to have occasional Hb H inclusion bodies upon review. Four of 303 cases (1.3%) were negative for the αEEP but positive for the Hb H inclusion test. Of these four cases, two (50%) showed heterozygous Southeast Asian (SEA) type deletion, one (25%) showed Hb Quong Sze mutation, and one (25%) showed no mutation detected upon molecular testing. All the Hb E trait cases with no Hb H inclusions and the negative control group showed the absence of the αEEP. The sensitivity and specificity of αEEP for detecting SEA deletion were 93.8% and 100% respectively, which is superior to the Hb H inclusion test (sensitivity 81.3%, specificity 95.2%). The αEEP is found to be a more sensitive method than the Hb H inclusion body test in the screening of α-thalassaemia trait in our Chinese population, in which SEA type deletion is prevalent. Further study is needed to explore the utility of the αEEP in the screening of α-thalassaemia traits in other populations. The exact nature of the αEEP is yet to be defined.

Iron Deficiency among School-Aged Adolescents in Hong Kong: Prevalence, Predictors, and Effects on Health-Related Quality of Life

Iron deficiency (ID) is a prevalent nutritional deficiency affecting children/adolescents worldwide. We reported (1) the prevalence of ID and ID with anemia (IDA) among Chinese school-aged adolescents, (2) clinical and dietary predictors of iron status, and (3) its impact on health-related qualities of life (HRQoL). This cross-sectional study recruited 183 boys and 340 girls (mean age = 17.55) from 16 schools in Hong Kong. ID is defined as serum ferritin <15 μg/L. The participants reported their dietary habits, menstrual patterns (girls), and HRQoL using structured questionnaires. The overall prevalence of ID was 11.1%. None of the boys had ID or IDA. Among girls, the rate of ID was 17.1% and IDA was 10.9%. One-third (36.3%) reported a regular habit of skipping ≥1 meal/day. Lower ferritin was found in adolescents who skipped meals (Est = -35.1, p = 0.017). Lower ferritin is correlated with poorer school functioning (Est = 0.81, p = 0.045) and fatigue (Est = 0.92, p = 0.016). Skipping meals is associated with poorer physical (p = 0.0017) and school functioning (p = 0.027). To conclude, 1 in 10 school-aged adolescents in Hong Kong are iron-deficient. The ID rate in girls (17.1%) is similar to that in other industrialized countries (5.2-16.6%). Future work should promote awareness on the potential health consequences of poor dietary habits on ID and the well-being of adolescents.

Severity scoring system to guide transfusion management in pediatric non-deletional HbH

BACKGROUND

Hemoglobin (Hb) H is generally recognized as mild thalassemia, despite its actual phenotypic diversity. A disease severity scoring system to guide initiation of regular transfusion among severely affected pediatric patients has not previously been reported.

METHODS

Patients with HbH were classified into transfusion-dependent thalassemia (TDT) and non-transfusion-dependent thalassemia (NTDT) as a surrogate for disease severity. Alpha-globin genotypes and relevant clinical parameters associated with TDT were identified. Univariate and multiple logistic regression analyses were performed to yield the most suitable severity scoring system.

RESULTS

From 246 patients with a median age of 14.3 (interquartile range 9.9-18.4) years initially enrolled into the study, the chance of having severe disease and developing TDT was remarkable only among patients with non-deletional HbH, for whom the scoring system was developed. Univariate and multiple logistic regression analyses resulted in three retained parameters associated with TDT, β-coefficients of which were used to develop the score. The final scoring system comprised age at diagnosis <2 years (score = 1), spleen size ≥3 cm (score = 1) and Hb at steady-state <7 (score = 4) or 7-8 g/dL (score = 3). A cutoff score ≥4 was associated with severe disease likely requiring regular transfusion (sensitivity 89.3%, specificity 81.4%), given regular transfusion resulted in maintained growth. The scoring system was validated in the second cohort of 77 non-deletional HbH, from which comparable sensitivity and specificity were obtained.

CONCLUSION

The newly developed scoring system was practical and helpful to highlight severely affected pediatric non-deletional HbH patients with potential needs of regular transfusion. This can be used as a guide for optimal treatment and disease monitoring in the future.

Clinical and genetic characteristics of hemoglobin H disease in Iran

Hemoglobin H (Hb H) disease is a subtype of α-thalassemia caused by deletional and/or non-deletional mutations in three alpha-globin genes in which the various genotypes determine the disease severity. This study was aimed to investigate the frequency of alpha gene mutations and genotypes and their correlation with hematological and clinical characteristics in Iran. Among 202 patients diagnosed with Hb H disease through a national study in Iran according to standard methods, we had access to the hematologic and clinical findings and genetic data of 101 patients in whom genetic study was performed. Genomic DNA from peripheral blood was extracted and analyzed for identification of α-globin gene mutations using Multiplex Gap Polymerase Chain Reaction, Reverse Hybridization Assay, and finally Direct DNA Sequencing method. Twenty-one different mutations and thirty genotypes were detected in 101 patients with Hb H disease. In total, 39 patients (38.6%) were deletional and 62 patients (61.4%) were non-deletional type of the disease. The _--^MED mutation was highly prevalent in almost half of the patients (56.4%). Among various genotypes, -^MED/-a^3.7 (29.7%) and -α^20.5/-α^5NT (6.9%) were the most prevalent genotypes found in the studied group. Patients with non-deletional type presented with more severe hematological and clinical findings. Hb H percentage and serum ferritin levels were significantly higher in non-deletional patients in comparison to the deletional group (p < 0.05). 12 (11.9%) and 40 (39.6%) out of 101 patients were on regular and occasional transfusions, respectively. 83% of those with regular transfusion belonged to the non-deletional group. Among transfusion-dependent patients, -^MED/α^CSα and α^20.5/-α^5NT were the most common genotypes. In this study, two patients with -α^20.5/α^CSα and -^MED/α^-5NT genotypes experienced thrombotic events. This study indicated that although non-deletional genotypes of Hb H disease were responsible for more clinical severity of the disease, due to the presence of severe phenotypes even in deletional types, no definite correlation was found between genotype and phenotype.

NGS4THAL, a one-stop molecular diagnosis and carrier screening tool for thalassemia and other hemoglobinopathies by next-generation sequencing

Thalassemia is one of the most common genetic diseases and a major health threat worldwide. Accurate, efficient and scalable analysis of next-generation sequencing (NGS) data is much needed for its molecular diagnosis and carrier screening. We developed NGS4THAL, a bioinformatics analysis pipeline analyzing next generation sequencing (NGS) data to detect pathogenic variants for thalassemia and other hemoglobinopathies. NGS4THAL realigns ambiguously mapped NGS reads derived from the homologous hemoglobin gene clusters for accurate detection of point mutations and small insertion/deletions (InDels). It uses a combination of complementary structural variant (SV) detection tools and an inhouse database of control data containing specific SVs to achieve accurate detection of the complex SV types. Detected variants are matched with those in HbVar database, allowing recognition of known pathogenic variants, including disease modifiers. Tested on simulation data, NGS4THAL achieved high sensitivity and specificity. For targeted NGS sequencing data from samples with laboratory-confirmed pathogenic hemoglobin variants, it achieved 100% detection accuracy. Application of NGS4THAL on whole genome sequencing data from unrelated studies revealed thalassemia mutation carrier rates for Hong Kong Chinese and Northern Vietnamese that were consistent with previous reports. NGS4THAL is a highly accurate and efficient molecular diagnosis tool for thalassemia and other hemoglobinopathies based on tailored analysis of NGS data and is potentially scalable for population carrier screening.

Comprehensive analysis of recessive carrier status using exome and genome sequencing data in 1543 Southern Chinese

Traditional carrier screening has been utilized for the detection of carriers of genetic disorders. Since a comprehensive assessment of the carrier frequencies of recessive conditions in the Southern Chinese population is not yet available, we performed a secondary analysis on the spectrum and carrier status for 315 genes causing autosomal recessive disorders in 1543 Southern Chinese individuals with next-generation sequencing data, 1116 with exome sequencing and 427 with genome sequencing data. Our data revealed that 1 in 2 people (47.8% of the population) was a carrier for one or more recessive conditions, and 1 in 12 individuals (8.30% of the population) was a carrier for treatable inherited conditions. In alignment with current American College of Obstetricians and Gynecologists (ACOG) pan-ethnic carrier recommendations, 1 in 26 individuals were identified as carriers of cystic fibrosis, thalassemia, and spinal muscular atrophy in the Southern Chinese population. When the >1% expanded carrier screening rate recommendation by ACOG was used, 11 diseases were found to meet the criteria in the Southern Chinese population. Approximately 1 in 3 individuals (35.5% of the population) were carriers of these 11 conditions. If the 1 in 200 carrier frequency threshold is used, and additional seven genes would meet the criteria, and 2 in 5 individuals (38.7% of the population) would be detected as a carrier. This study provides a comprehensive catalogue of the carrier spectrum and frequency in the Southern Chinese population and can serve as a reference for careful evaluation of the conditions to be included in expanded carrier screening for Southern Chinese people.

An Evaluation for the Causes of Reduced Hb A2 and the Molecular Characterization of HBD Variants in Hong Kong

Prenatal screening of β-thalassemia (β-thal) carriers is based on the hallmark phenotype of microcytosis and raised Hb A₂. The unanticipated birth of β-thal major (β-TM) offspring to β-thal carriers who were misdiagnosed during prenatal screening have been reported. A subset of these resulted from the masked phenotype due to the coinheritance of HBD variants. In a broader sense, the causes of reduced Hb A₂ in thalassemia screening, the prevalence and spectrum of HBD variants in Hong Kong remain to be characterized. Over a 13-month period, a total of 2982 samples were referred for thalassemia screening. Surplus samples with reduced Hb A₂ levels (2.0%) were evaluated. HBD variations were assessed by direct sequencing. Sixty-six samples were tested. Hb H disease, HBD variants, α-thalassemia (α-thal) trait and iron deficiency were detected in 40 (60.6%), 12 (18.2%), eight (12.1%) and seven (10.6%) samples, respectively. Seven samples carried more than one of the mentioned conditions. The cause remained elusive in seven samples. Thirteen HBD variants were detected and two were recurrent, including HBD: c.-127T>C [-77 (T>C)] and HBD: c.314G>A (Hb Chori-Burnaby). A novel nonsense variant HBD: c.262C>T [codon 87 (C>T)] was detected in cis with HBD: c.-127T>C. Overall, the prevalence of HBD variants was 0.4%. This study advanced our understanding of the causes of reduced Hb A₂ in clinical practice and identified hereditary disorders of α- and δ-globin genes as the prevailing causes. It established the landscape of HBD variations in our locality and highlighted the pitfall of phenotypic screening of β-thal carriers.

Preconception risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease

BACKGROUND

Globally, about 6% of children are born with a serious birth defect of genetic or partially genetic origin. Carrier screening or testing is one way to identify couples at increased risk of having a child with an autosomal recessive condition. The most common autosomal recessive conditions are thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease, with higher carrier rates in high-risk populations of specific ancestral backgrounds. Identifying and counselling couples at genetic risk of the conditions before pregnancy enables them to make fully informed reproductive decisions, with some of these choices not being available if testing is only offered in an antenatal setting. This is an update of a previously published review.

OBJECTIVES

To assess the effectiveness of systematic preconception genetic risk assessment to enable autonomous reproductive choice and to improve reproductive outcomes  in women and their partners who are both identified as carriers of thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease in healthcare settings when compared to usual care.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Registers. Date of latest search of the registers: 04 August 2021. In addition, we searched for all relevant trials from 1970 (or the date at which the database was first available if after 1970) to date using electronic databases (MEDLINE, Embase, CINAHL, PsycINFO), clinical trial databases (National Institutes of Health, Clinical Trials Search portal of the World Health Organization, metaRegister of controlled clinical trials), and hand searching of key journals and conference abstract books from 1998 to date (European Journal of Human Genetics, Genetics in Medicine, Journal of Community Genetics). We also searched the reference lists of relevant articles, reviews and guidelines and also contacted subject experts in the field to request any unpublished or other published trials. Date of latest search of all these sources: 25 June 2021.  SELECTION CRITERIA: Any randomised controlled trials (RCTs) or quasi-RCTs (published or unpublished) comparing reproductive outcomes of systematic preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease when compared to usual care.

DATA COLLECTION AND ANALYSIS

We identified 37 papers, describing 22 unique trials which were potentially eligible for inclusion in the review. However, after assessment, we found no RCTs of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease.

MAIN RESULTS

No RCTs of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease are included. A trial identified earlier has published its results and has subsequently been listed as excluded in this review.

AUTHORS' CONCLUSIONS

As there are no RCTs of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis, or Tay-Sachs disease included in either the earlier or current versions of this review, we recommend considering potential non-RCTs studies (for example prospective cohorts or before-and-after studies) for future reviews. While RCTs are desirable to inform evidence-based practice and robust recommendations, the ethical, legal and social implications associated with using this trial design to evaluate the implementation of preconception genetic risk assessment involving carrier testing and reproductive autonomy must also be considered.  In addition, rather than focusing on single gene-by-gene carrier testing for specific autosomal-recessive conditions as the intervention being evaluated, preconception expanded genetic screening should also be included in future searches as this has received much attention in recent years as a more pragmatic strategy. The research evidence for current international policy recommendations is limited to non-randomised studies.

Outcomes of allogeneic transplantation for hemoglobin Bart's hydrops fetalis syndrome in Hong Kong

BACKGROUND

Hemoglobin Bart's hydrops fetalis syndrome (BHFS) was once considered a fatal condition universally. Medical advances over the past three decades have resulted in increasing numbers of BHFS survivors. This retrospective review summarized local territory-wide experience and outcomes of BHFS patients who received allogeneic hematopoietic stem cell transplantation (HSCT) in Hong Kong.

METHODS

All BHFS patients who underwent allogeneic HSCT in Hong Kong, either in one of the two former pediatric transplant centers (Queen Mary Hospital and Prince of Wales Hospital) on or before 2019 or in the single territory-wide pediatric transplant center (Hong Kong Children's Hospital) since 2019, from January 1, 1996, till December 31, 2020, were included. Basic demographic data, perinatal history, transplant details, long-term outcomes, and morbidities were reviewed.

RESULTS

Total five allogeneic HSCT were performed in two males and three females at a median age of 22 months, which include one 8/8 matched-sibling bone marrow transplant, one 5/6 matched-sibling cord blood transplant with HLA-DR antigenic mismatch, two 12/12 matched-unrelated peripheral blood stem cell transplant (PBSCT), and one haploidentical PBSCT with TCRαβ/CD45RA depletion from maternal donor. Neutrophil and platelet engrafted (>20 × 10⁹ /L) at a median of 15 and 22 days, respectively. All achieved near full donor chimerism at 1 month. All patients survived and remained transfusion-independent without significant morbidities with median follow-up duration of 10 years.

CONCLUSION

To conclude, local data demonstrated favorable outcome of allogeneic HSCT for BHFS patients, but sample number is small. Non-directive approach in counseling and international collaboration is recommended.

Clinical Implementation of Expanded Carrier Screening in Pregnant Women at Early Gestational Weeks: A Chinese Cohort Study

Demands for expanded carrier screening (ECS) are growing and ECS is becoming an important part of obstetrics practice and reproductive planning. The aim of this study is to evaluate the feasibility of a small-size ECS panel in clinical implementation and investigate Chinese couples’ attitudes towards ECS. An ECS panel containing 11 recessive conditions was offered to Chinese pregnant women below 16 gestational weeks. Sequential testing of their partners was recommended for women with a positive carrier status. The reproductive decision and pregnancy outcome were surveyed for at-risk couples. A total of 1321 women performed ECS successfully and the overall carrier rate was 19.23%. The estimated at-risk couple rate was 0.83%. Sequential testing was performed in less than half of male partners. Eight at-risk couples were identified and four of them performed prenatal diagnosis. Our study demonstrated that a small-size ECS panel could yield comparable clinical value to a larger-size panel when the carrier rate of the individual condition is equal or greater than 1%. In addition, more than half of male partners whose wives were carriers declined any types of sequential testing possibly due to a lack of awareness and knowledge of genetic disorders. Genetic education is warranted for the better implementation of ECS.

Evaluation of Ion Torrent next-generation sequencing for thalassemia diagnosis

INTRODUCTION

To evaluate a next-generation sequencing (NGS) workflow in the screening and diagnosis of thalassemia.

METHODS

In this prospective study, blood samples were obtained from people undergoing genetic screening for thalassemia at our centre in Guangzhou, China. Genomic DNA was polymerase chain reaction (PCR)-amplified and sequenced using the Ion Torrent system and results compared with traditional genetic analyses.

RESULTS

Of the 359 subjects, 148 (41%) were confirmed to have thalassemia. Variant detection identified 35 different types including the most common. Identification of the mutational sites by NGS were consistent with those identified by Sanger sequencing and Gap-PCR. The sensitivity and specificities of the Ion Torrent NGS were 100%. In a separate test of 16 samples, results were consistent when repeated ten times.

CONCLUSION

Our NGS workflow based on the Ion Torrent sequencer was successful in the detection of large deletions and non-deletional defects in thalassemia with high accuracy and repeatability.

Mutation spectrum and erythrocyte indices characterisation of α-thalassaemia and β-thalassaemia in Sichuan women in China: a thalassaemia screening survey of 42 155 women

AIMS

The present study aims to investigate the mutation spectrum of thalassaemia, and characterise the erythrocyte indices of thalassaemia in a large cohort in Sichuan, which is a province with a high prevalence of thalassaemia in southern China.

METHODS

The present study was conducted from July 2017 to July 2019. A total of 42 155 women screened for thalassaemia were enrolled. The thalassaemia carriers were screened by erythrocyte analysis and haemoglobin electrophoresis. Then, the screening test results and genetic results were collected.

RESULTS

A total of 1109 individuals had thalassaemia gene defects. Among these individuals, 69.7% were α-thalassaemia (α-thal) and 28.6% were β-thalassaemia (β-thal). For α-thal defects, carriers with ^--SEA had the lowest mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH) values. For β-thal defects, carriers with heterozygous haemoglobin E and -28 had the highest MCV and MCH values. In addition, an MCV cut-off of 80 fl and an MCH cut-off of 27 pg was able to detect 99.1% α0 thalassaemia and 99.7% β0/β+ thalassaemia; however, that criterion could result in a great number of false-negative results in α+ carriers.

CONCLUSION

A criterion of MCV <80 fl and MCH <27 pg is recommended for detecting -SEA carriers and β0/β+ carriers, while higher cut-offs are needed to detect α+ carriers.

α-Globin Genotypes Associated with Hb H Disease: A Report from Oman and a Review of the Literature from the Eastern Mediterranean Region

α-Thalassemia (α-thal) is the most common autosomal recessive hemoglobinopathy. There is a vast diversity and geographical variability in underlying genotypes in Hb H (β4) patients. Herein, we describe the genotypes found in the largest report of Omani Hb H patients. Moreover, we reviewed and summarized the literature published from the Eastern Mediterranean region. A retrospective review of all genetically confirmed Hb H disease patients diagnosed between 2007 and 2017 at Sultan Qaboos University Hospital, Muscat, Oman, was performed. Hematological parameters and clinical presentations were assessed. Both α-globin genes were screened for deletional and nondeletional mutations using a stepwise diagnostic strategy as described before. A total of 52 patients (27 females and 25 males) with a mean age of 20.6 years (range 0.23-80.0) were molecularly confirmed to carry Hb H disease. The patients had a hemoglobin (Hb) level of 9.3 g/dL (range 5.7-13.0) and mean corpuscular volume (MCV) of 58.4 fL (range 48.2-82.1). A total of eight genotype combinations were identified, with α2 polyadenylation signal mutation (polyA1) (AATAAA>AATAAG (α^PA1α/α^PA1α), often cited as α^T-Saudiα/α^T-Saudiα, being the most common (53.8%) followed by -α^3.7/- -^{MED I} (28.8%). Our cohort also included patients with combinations of α^PA1 with other Hb variants: α^PA1α/α^PA1α with Hb S (HBB: c.20A>T) trait (n = 2), -α^3.7/α^PA1α (n = 2) and α^{codon 19}α (HBA2: c.56delG)/α^PA1α (n = 1). Nondeletional Hb H disease due to the α^PA1 mutation is the most common in Omanis. Molecular diagnosis is necessary for accurate confirmation of the diagnosis of α-thal, determination of underlying genotypes, follow-up and counseling.

Editing aberrant splice sites efficiently restores β-globin expression in β-thalassemia

The thalassemias are compelling targets for therapeutic genome editing in part because monoallelic correction of a subset of hematopoietic stem cells (HSCs) would be sufficient for enduring disease amelioration. A primary challenge is the development of efficient repair strategies that are effective in HSCs. Here, we demonstrate that allelic disruption of aberrant splice sites, one of the major classes of thalassemia mutations, is a robust approach to restore gene function. We target the IVS1-110G>A mutation using Cas9 ribonucleoprotein (RNP) and the IVS2-654C>T mutation by Cas12a/Cpf1 RNP in primary CD34+ hematopoietic stem and progenitor cells (HSPCs) from β-thalassemia patients. Each of these nuclease complexes achieves high efficiency and penetrance of therapeutic edits. Erythroid progeny of edited patient HSPCs show reversal of aberrant splicing and restoration of β-globin expression. This strategy could enable correction of a substantial fraction of transfusion-dependent β-thalassemia genotypes with currently available gene-editing technology.

Gene spectrum analysis of thalassemia for people residing in northern China

BACKGROUND

Southern China provinces have high incidence of thalassemia, however, sporadic cases can be found in northern China as well.

METHODS

People resided in north China who were suspected to have thalassemia were detected mutations by gap-polymerase chain reaction (Gap-PCR) and reverse dot blot (RDB) analyses. Those with positive findings from 2012 to 2017 were further analyzed for basic clinical data and ancestral information either by medical records or by telephone follow-up or both.

RESULTS

Most people enrolled in our study had no or mild symptoms. For those with positive gene findings, people originated from the north had higher percentage of β-thalassemia gene mutations compared with those originated from the south (72.8% vs. 62.4%, χ2 = 9.92, P = 0.001). Analysis of the individual gene distribution of people from south and north areas did not show significant difference either in α- thalassemia (P = 0.221) or β-thalassemia (P = 0.979). No significant difference was found in the frequency of α mutation in people living in different altitudes. However, for β-thalassemia, the frequency of the 6 most common mutations was significantly different in people living in different provinces with altitude below 500 m, 500-1000 m, and above 1000 m (χ2 test, P < 0.05).

CONCLUSION

Most of people in north China with thalassemia mutation gene were thalassemia carriers. People originated from the north had higher frequency of β mutation than those originated from the south, but the north people had similar individual gene mutation profile compared with south people both for α and β mutations. People lived in different altitudes had different spectrum of β mutations.

Molecular Spectrum of α- and β-Thalassemia Mutations in a Large Ethnic Hakka Population in Southern China

Thalassemia is one of the most prevalent inherited disorders in southern China. However, there have been few reports on molecular characterization of α- and β-thalassemia (α- and β-thal) in the large Hakka population living in Meizhou, a city with high incidence of thalassemia in China. A total of 11,631 in- and outpatients in the Hakka area were analyzed by DNA-based α- and β-thal testing. Of all the samples, 4280 mutant chromosomes were detected, accounting in a total of 35.98%, of which 2864 (24.82%) α-thal mutants were detected, 1268 (10.09%) β-thal mutants were detected, 148 (1.27%) α- and β-thal mutants were detected. The following mutations - -^SEA/αα (Southeast Asian deletion), β^A/β^A; αα/αα, IVS-II-654 (C>T) (HBB: c.316-197C>T)/β^A; αα/αα, codons 41/42 (-TCTT) (HBB: c.126_129delCTTT)/β^A; and -α^3.7/αα, β^A/β^A were the most common thalassemia genotypes. The most common thalassemia genotype in the Hakka population in Meizhou was α-thal. In order to reduce the incidence of severe thalassemia in children, a prevention and control strategy should be established based on the distribution data of thalassemia genotyping. Our findings provide a valuable reference for clinical institutions or local governments to reduce the prevalence of thalassemia in the subtropical regions in the world.

Comparison between capillary zone electrophoresis and capillary isoelectric focusing for thalassemia screening in southern China

BACKGROUND

Capillary isoelectric focusing is a type of capillary electrophoresis method newly used for thalassemia screening in China. Although the good performance has been proved by several studies, whether it can best suit the special needs of Chinese patients still requires further investigations.

METHODS

Comparisons were made between capillary zone electrophoresis method applied on Sebia Minicap and capillary isoelectric focusing method applied on Helena V8 platform E-class on identifying Hb E, Hb CS, Hb H, and Hb Barts for patients from southern China. And mixing studies were used to evaluate the lowest detection limits of these 2 kinds of capillary electrophoresis system.

RESULTS

Helena V8 could not make a distinction between peaks of Hb E and peaks of Hb A2 as Sebia Minicap did. All chosen patients with Hb H and/or Hb Barts could be screened out by both 2 systems, but when analyzed by Helena V8, it was hard to distinguish Hb H from Hb Barts sometimes, while Sebia Minicap could make a clear distinction between peaks of Hb H and Hb Barts. Only a part of patients (3 of 8, 37.5%) with Hb CS could be screened out by Helena V8, while all patients could be identified by Sebia Minicap. Sebia Minicap had a lower detection limit for trace peaks than Helena V8 (near to 0.2% vs near to 0.6%).

CONCLUSIONS

Compared with capillary zone electrophoresis, capillary isoelectric focusing applied on Helena V8 maybe is not the first choice for hemoglobinopathy testing in southern China.

Variability in State-Based Recommendations for Management of Alpha Thalassemia Trait and Silent Carrier Detected on the Newborn Screen

We conducted an inventory of state-based recommendations for follow-up of alpha thalassemia silent carrier and trait identified on newborn screen. We found wide variability in the nature and timing of these recommendations. We recommend a standardized recommendation to guide pediatricians in evidenced-based care for this population.

Preconception risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease

BACKGROUND

Globally, about five per cent of children are born with congenital or genetic disorders. The most common autosomal recessive conditions are thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease, with higher carrier rates in specific patient populations. Identifying and counselling couples at genetic risk of the conditions before pregnancy enables them to make fully informed reproductive decisions, with some of these choices not being available if genetic counselling is only offered in an antenatal setting. This is an update of a previously published review.

OBJECTIVES

To assess the effectiveness of systematic preconception genetic risk assessment to improve reproductive outcomes in women and their partners who are identified as carriers of thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease in healthcare settings when compared to usual care.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Registers. In addition, we searched for all relevant trials from 1970 (or the date at which the database was first available if after 1970) to date using electronic databases (MEDLINE, Embase, CINAHL, PsycINFO), clinical trial databases (National Institutes of Health, Clinical Trials Search portal of the World Health Organization, metaRegister of controlled clinical trials), and hand searching of key journals and conference abstract books from 1998 to date (European Journal of Human Genetics, Genetics in Medicine, Journal of Community Genetics). We also searched the reference lists of relevant articles, reviews and guidelines and also contacted subject experts in the field to request any unpublished or other published trials.Date of latest search of the registers: 20 June 2017.Date of latest search of all other sources: 16 November 2017.

SELECTION CRITERIA

Any randomised or quasi-randomised controlled trials (published or unpublished) comparing reproductive outcomes of systematic preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease when compared to usual care.

DATA COLLECTION AND ANALYSIS

We identified 25 papers, describing 16 unique trials which were potentially eligible for inclusion in the review. However, after assessment, no randomised controlled trials of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease were found.

MAIN RESULTS

No randomised controlled trials of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease were included. One ongoing trial has been identified which may potentially eligible for inclusion once completed.

AUTHORS' CONCLUSIONS

As no randomised controlled trials of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis, or Tay-Sachs disease were found for inclusion in this review, the research evidence for current policy recommendations is limited to non-randomised studies.Information from well-designed, adequately powered, randomised trials is desirable in order to make more robust recommendations for practice. However, such trials must also consider the legal, ethical, and cultural barriers to implementation of preconception genetic risk assessment.

Molecular characterization of α- and β-thalassemia in the Yulin region of Southern China

Thalassemia is one of the most common hereditary blood disorders. Epidemiological data regarding the prevalence and distribution of mutations is important for planning a thalassemia control program. To reveal the prevalence of thalassemia and mutation spectrum in the Yulin region of southern China, we screened 130,318 individuals from Yulin region by hematological and genetic analysis. Totally, 24,886 (19.10%) subjects were diagnosed with thalassemia, including 16,308 (12.51%) subjects with α-thalassemia alone, 6658 (5.11%) subjects with β-thalassemia alone and 1920 (1.47%) subjects with both α- and β-thalassemia. Ten α-thalassemia mutations were identified in the α-thalassemia subjects, with the common α-thalassemia mutations being --^SEA mutation (51.91%), -α^3.7 (19.90%), α^CSα (10.58%), -α^4.2 (8.13%), α^WSα (7.67%). Thirteen β-thalassemia mutations and 31 genotypes were characterized in the β-thalassemia subjects. The seven common mutations [CD41-42 (-CTTT) (43.31%), CD17 (A > T) (34.58%), CD26 (G > A) (6.86%), CD71-72 (+A) (4.25%), -28 (A > G) (3.90%), IVS-II-654 (C > T) (3.53%) and IVS-I-1 (G > T) (2.22%)] accounted for 98.65% of all β-thalassemia defects. Furthermore, 6 cases of α-triplication and 3 cases of mutation -α^2.4 were first identified in this region. Our data illustrated that there was great heterogeneity and extensive spectrum of thalassemias in the Yulin populations. The findings will contribute an available reference for prevention of thalassemia in this region.

Cut-Off Values of Hematologic Parameters to Predict the Number of Alpha Genes Deleted in Subjects with Deletional Alpha Thalassemia

Most α-thalassemia cases are caused by deletions of the structural α-globin genes. The degree of microcytosis and hypochromia has been correlated with the number of affected α-globin genes, suggesting a promising role of hematologic parameters as predictive diagnostic tools. However, cut-off points for these parameters to discriminate between the different subtypes of α-thalassemia are yet to be clearly defined. Six hematologic parameters (RBC, Hb, MCV, MCH, MCHC and RDW) were evaluated in 129 cases of deletional α-thalassemia (56 heterozygous α⁺ thalassemia, 36 homozygous α⁺ thalassemia, 29 heterozygous α⁰ thalassemia and 8 cases of Hb H disease). A good correlation between the number of deleted alpha genes and MCV (r = −0.672, p < 0.001), MCH (r = −0.788, p < 0.001) and RDW (r = 0.633, p < 0.001) was observed. The presence of an α⁰ allele should be discarded in individuals with microcytosis without iron deficiency and normal values of Hb A₂ and Hb F with MCH < 23.40 pg. Furthermore, MCH < 21.90 pg and/or MCV < 70.80 fL are strongly suggestive of the presence of one α⁰ allele. Finally, an accurate presumptive diagnosis of Hb H disease can be made if both RDW ≥ 20% and MCH < 19 pg are seen.

First Report of Hb Kent [β37(C3)Trp→Cys (TGG>TGC) HBB: c.114G>C] in a Chinese Family

We report a novel HBB: c.114G>C mutation in a Chinese family. This mutation resulted in a β37(C3)Trp→Cys amino acid substitution and was synonymous with Hb Kent, a hemoglobin (Hb) variant that was reported exclusively in patients of European descent. Though Hb Kent has a normal oxygen affinity and molecular stability, it has a characteristic dual variant appearance on cellulose acetate electrophoresis (CAE) and high performance liquid chromatography (HPLC) caused by the posttranslational modification of cysteine. We also report the phenotypic expression of this variant when coinherited with the Southeast Asian (- -^SEA) double α-globin gene deletion.

An international registry of survivors with Hb Bart's hydrops fetalis syndrome

Hemoglobin (Hb) Bart's hydrops fetalis syndrome (BHFS) resulting from α0-thalassemia is considered a universally fatal disorder. However, over the last 3 decades, improvements in intrauterine interventions and perinatal intensive care have resulted in increasing numbers of BHFS survivors. We have initiated an international registry containing information on 69 patients, of which 31 are previously unpublished. In this perspective, we analyze the available clinical information to document the natural history of BHFS. In the future, once we have accrued sufficient cases, we aim to build on this study and provide information to allow counseling of at-risk couples. To date, 39 patients have survived beyond the age of 5 years, 18 of whom are now older than 10 years. Based on the available cases, we find evidence to suggest that intrauterine therapy provides benefits during the perinatal and neonatal period; however, it may not provide additional benefits to long-term growth and neurodevelopmental outcomes. Growth retardation is a major adverse long-term outcome among BHFS patients with ∼40% being severely affected in terms of weight and ∼50% in terms of height. There is also an increased risk of neurodevelopmental delay as we find 20% (11/55) of BHFS survivors suffer from a serious delay of ≥6 months. Most patients in the registry require lifelong transfusion and often have associated congenital abnormalities and comorbidities. This perspective is a first step in gathering information to allow provision of informed counseling on the predicted outcomes of affected babies.

Hematopoietic stem cell transplantation for people with ß-thalassaemia major

BACKGROUND

Thalassemia is an inherited autosomal recessive blood disorder, caused by mutations in globin genes or their regulatory regions. This results in a reduced rate of synthesis of one of the globin chains that make up haemoglobin. In ß-thalassaemia major there is an underproduction of ß-globin chains combined with excess of free α-globin chains. The excess free α-globin chains precipitate in red blood cells, leading to their destruction (haemolysis) and ineffective erythropoiesis. The conventional approach to treatment is based on the correction of haemoglobin status through regular blood transfusions and iron chelation therapy for iron overload. Although conventional treatment has the capacity to improve the quality of life of people with ß-thalassaemia major, allogeneic hematopoietic stem cell transplantation is the only currently available procedure which has the curative potential. This is an update of a previously published Cochrane Review.

OBJECTIVES

To evaluate the effectiveness and safety of different types of allogeneic hematopoietic stem cell transplantation, in people with severe transfusion-dependant ß-thalassaemia major, ß-thalassaemia intermedia or ß0/+- thalassaemia variants requiring chronic blood transfusion.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Haemoglobinopathies Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.Date of the most recent search: 18 August 2016.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials comparing allogeneic hematopoietic stem cell transplantation with each other or with standard therapy (regular transfusion and chelation regimen).

DATA COLLECTION AND ANALYSIS

Two review authors independently screened studies and had planned to extract data and assess risk of bias using standard Cochrane methodologies but no studies were identified for inclusion.

MAIN RESULTS

No relevant studies were retrieved after a comprehensive search of the literature.

AUTHORS' CONCLUSIONS

We were unable to identify any randomised controlled trials or quasi-randomised controlled trials on the effectiveness and safety of different types of allogeneic stem cell transplantation in people with severe transfusion-dependant ß-thalassaemia major or ß0/+- thalassaemia variants requiring chronic blood transfusion. The absence of high-level evidence for the effectiveness of these interventions emphasises the need for well-designed, adequately-powered, randomised controlled clinical trials.

Mugineic acid, active ingredient of wheat grass: an oral novel hexadentate iron chelator in iron overloaded diseases

Iron chelation therapies are required for the treatment of iron overloaded patients; nonetheless, their side effects are also well known. We have evaluated iron-chelating activity of wheat grass extract (WHE) and its purified compound, mugineic acid in murine model with phenylhydrazine (PHZ) and dextran induced acute and chronic iron overload conditions. PHZ and dextran treatment induced acute and chronic iron overload condition in mice, respectively, as indicated by increased serum and tissue iron in both cases. Iron overload was also accompanied with haemosiderosis in tissues (liver and spleen). These PHZ and dextran -: treated mice were orally treated with either crude WHE or purified mugineic acid. The efficacy of mugineic acid and WHE was compared with the potent oral iron chelator ICL670 (Exjade). PHZ and dextran treatment followed by oral administration of WHE or mugineic acid significantly checked the rise of serum/plasma levels of iron as well as tissue iron and also, haemosiderosis in tissues. The results are highly comparable with known iron chelator ICL670. WHE and purified mugineic acid, both seem to have significant prospect to be the cheap, non-toxic, hexadentate and oral therapeutic agents to prevent or alleviate toxic iron overload in patients.

Clinical Effect and Mechanism of Yisui Shengxue Granules in Thalassemia Patients with Mild, Moderate, or Severe Anemia

Yisui Shengxue granules, which is a Chinese traditional medicine, can increase hemoglobin, red blood cells, and Ret of thalassemia patients with mild, moderate, and severe anemia and thus relieve clinical anemia symptoms. Studies on mechanism found that Yisui Shengxue granules can increase the proliferation ability of hematopoietic stem cells. Emodin promoted colony forming of hematopoietic stem cells. Yisui Shengxue granules can increase the activity of GSH-PX in bone marrow blood and decreased the severity of inclusion bodies on the cytomembrane of RBCs. YSSXG attenuated anemia symptoms in patients with thalassemia mostly by increasing the proliferation of hematopoietic stem cells and decreasing the hemolysis of RBCs.

A Fetus with Hb Bart's Disease Due to Maternal Uniparental Disomy for Chromosome 16

We here report an unusual case of Hb Bart's (γ4) disease. Thalassemia screening of a couple showed that the wife was an α(0)-thalassemia (α(0)-thal) carrier and her husband's mean corpuscular volume (MCV) was normal. Chorionic villus sampling (CVS) was performed at 13 weeks' gestation for positive Down syndrome screening and chromosomal study of the cultured CVS showed a normal karyotype. Ultrasound examination at 22 weeks' gestation showed fetal cardiomegaly and raised middle cerebral artery peak systolic velocity. Cordocentesis confirmed fetal anemia and showed Hb Bart's disease. Multiplex gap-polymerase chain reaction (gap-PCR) for α-thal deletions on DNA extracted from the CVS showed the presence of a homozygous α(0)-thal - -(SEA) (Southeast Asian) deletion. The husband was found to be a carrier of the α(+)-thal -α(3.7) (rightward) deletion. Non paternity was excluded by fluorescent PCR using short tandem repeat (STR) markers on chromosomes 13, 18 and 21. A de novo terminal deletion of chromosome 16 was excluded by array comparative genomic hybridization (aCGH). Detection of uniparental disomy (UPD), using STR markers on chromosome 16 showed maternal uniparental isodisomy from 16pter to 16p13.2, and uniparental heterodisomy from 16p13.13 to 16qter.

Preconception risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease

BACKGROUND

Globally, about five per cent of children are born with congenital or genetic disorders. The most common autosomal recessive conditions are thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease, with higher carrier rates in specific patient populations. Identifying and counselling couples at genetic risk of the conditions before pregnancy enables them to make fully informed reproductive decisions, with some of these choices not being available if genetic counselling is only offered in an antenatal setting.

OBJECTIVES

To assess the effectiveness of systematic preconception genetic risk assessment to improve reproductive outcomes in women and their partners who are identified as carriers of thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease in healthcare settings when compared to usual care.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Registers. In addition, we searched for all relevant trials from 1970 (or the date at which the database was first available if after 1970) to date using electronic databases (MEDLINE, Embase, CINAHL, PsycINFO), clinical trial databases (National Institutes of Health, Clinical Trials Search portal of the World Health Organization, metaRegister of controlled clinical trials), and hand searching of key journals and conference abstract books from 1998 to date (European Journal of Human Genetics, Genetics in Medicine, Journal of Community Genetics). We also searched the reference lists of relevant articles, reviews and guidelines and also contacted subject experts in the field to request any unpublished or other published trials.Date of latest search of the registers: 25 June 2015.Date of latest search of all other sources: 10 December 2014.

SELECTION CRITERIA

Any randomised or quasi-randomised control trials (published or unpublished) comparing reproductive outcomes of systematic preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease when compared to usual care.

DATA COLLECTION AND ANALYSIS

We identified 19 papers, describing 13 unique trials which were potentially eligible for inclusion in the review. However, after assessment, no randomised controlled trials of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease were found.

MAIN RESULTS

No randomised controlled trials of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease were found.

AUTHORS' CONCLUSIONS

As no randomised controlled trials of preconception genetic risk assessment for thalassaemia, sickle cell disease, cystic fibrosis, or Tay-Sachs disease were found for inclusion in this review, the research evidence for current policy recommendations is limited to non-randomised studies.Information from well-designed, adequately powered, randomised trials is desirable in order to make more robust recommendations for practice. However, such trials must also consider the legal, ethical, and cultural barriers to implementation of preconception genetic risk assessment.

In utero hematopoietic cell transplantation for hemoglobinopathies

In utero hematopoietic cell transplantation (IUHCTx) is a promising strategy to circumvent the challenges of postnatal hematopoietic stem cell (HSC) transplantation. The goal of IUHCTx is to introduce donor cells into a naïve host prior to immune maturation, thereby inducing donor–specific tolerance. Thus, this technique has the potential of avoiding host myeloablative conditioning with cytotoxic agents. Over the past two decades, several attempts at IUHCTx have been made to cure numerous underlying congenital anomalies with limited success. In this review, we will briefly review the history of IUHCTx and give a perspective on alpha thalassemia major, one target disease for its clinical application.

Genetic basis of persistent red blood cell microcytosis in the Chinese unexplained by phenotypical testing

AIMS

Hypochromic microcytic anaemia is the hallmark phenotype of thalassaemia. Current phenotypical tests do not provide a diagnosis in a small proportion of patients with red blood cell microcytosis. We aim to evaluate the genetic basis of red cell microcytosis in these cases in our Chinese population.

METHODS

We identified from a large cohort of 1684 unselected requests for thalassaemia testing 23 Chinese subjects who had unexplained microcytosis after phenotypical iron and haemoglobin studies. In 18 of these subjects with available DNA, extensive genotypical analysis of the α and β globin gene cluster was performed, including gap-PCR, multiplex amplification-refractory mutation system, Sanger sequencing and multiplex ligation-dependent probe amplification.

RESULTS

Occult single and double α globin gene (HBA1, HBA2) deletions and α thalassaemic haemoglobinopathies (Haemoglobin Quong Sze, Haemoglobin Constant Spring) were the genetic basis for the microcytosis. Occult β globin gene (HBB) mutations and δ globin gene (HBD) abnormalities masking β thalassaemia are not seen.

CONCLUSIONS

A cost-effective genotyping approach for the detection of these occult globin gene mutations can be proposed. The identification of these mutations is important for making a diagnosis and for the provision of accurate genetic counselling. (This paper adds to our understanding of the genetic basis of red blood cell microcytosis in clinical practice, and it provides a cost-effective approach for genotyping in diagnostic laboratories).

Hematopoietic stem cell transplantation for people with ß-thalassaemia major

BACKGROUND

Thalassemia is an inherited blood disorder, caused by mutations in regulatory genes and transmitted as an autosomal recessive disorder, which results in a reduced rate of synthesis of one of the globin chains that make up haemoglobin. In ß-thalassaemia major there is an underproduction of ß-globin chains combined with excess of free α-globin chains. The excess free α-globin chains damage the red blood cell membranes, leading to their destruction and a phenomenon termed ineffective erythropoiesis. The conventional approach to treatment is based on the correction of haemoglobin status through regular blood transfusions and iron chelation therapy for iron overload. Although conventional treatment has the capacity to improve the quality of life of people with ß-thalassaemia major, allogeneic hematopoietic stem cell transplantation is the only currently available procedure which has the potential to definitively cure the disease.

OBJECTIVES

To evaluate the effectiveness and safety of different types of allogeneic hematopoietic stem cell transplantation, in people with severe transfusion-dependant ß-thalassaemia major, ß-thalassaemia intermedia or ß0/+- thalassaemia variants requiring chronic blood transfusion.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Haemoglobinopathies Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.Date of the most recent search: 11 November 2013.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials comparing allogeneic hematopoietic stem cell transplantation with each other or with standard therapy (regular transfusion and chelation regimen).

DATA COLLECTION AND ANALYSIS

Two review authors independently screened studies and had planned to extract data and assess risk of bias using standard Cochrane Collaboration methodologies but no studies were identified for inclusion.

MAIN RESULTS

No relevant studies were retrieved after a comprehensive search of the literature.

AUTHORS' CONCLUSIONS

We were unable to identify any randomised controlled trials or quasi-randomised controlled trials on the effectiveness and safety of different types of allogeneic stem cell transplantation in people with severe transfusion-dependant ß-thalassaemia major or ß0/+- thalassaemia variants requiring chronic blood transfusion. The absence of high-level evidence for the effectiveness of these interventions emphasises the need for well-designed, adequately-powered, randomised controlled clinical trials.

Diagnosis and prevention of thalassemia

Thalassemia is the most common monogenic inherited disease worldwide and it affects most countries to various extents. This review summarizes the current approaches to phenotypic and genotypic diagnosis of thalassemia in clinical practice. Prevention strategies that encompass carrier screening, genetic counseling and prenatal diagnosis are discussed. The importance of public education and an awareness of a changing perception regarding this group of diseases are emphasized. It also addresses the impact of the rapidly increasing knowledge in disease severity modification by hemoglobin F (Hb F).

Evaluation of the new red cell parameters on Beckman Coulter DxH800 in distinguishing iron deficiency anaemia from thalassaemia trait

INTRODUCTION

The new red blood cell (RBC) parameters such as reticulocyte haemoglobin content and percentage of hypochromic red cells or equivalent, although useful in the laboratory assessment of iron deficiency anaemia (IDA), are confounded by thalassaemia trait (TT). We aim to evaluate the new red cell parameters on the Beckman Coulter DxH800 in distinguishing between IDA and TT.

METHODS

A total of 246 normal subjects, 102 patients with IDA and 115 subjects with TT were accrued for the study. The parameters studied were red blood cell size factor (RSF), low haemoglobin density (LHD%), microcytic anaemia factor (MAF), standard deviation of conductivity of the nonreticulocyte population (SD-C-NRET) and unghosted cell (UGC). Comparison between groups was performed by Student's t-test, and the diagnostic performance was determined by receiver operating characteristic (ROC) curve analysis.

RESULTS

Both the LHD% and RSF were significantly higher in IDA than TT, whereas MAF and SD-C-NRET were significantly lower. The SD-C-NRET showed the best diagnostic performance as a single parameter. A formula, [(RBC + Hb) × (HCT + SD-C-NRET)]/RDW-SD, was devised to distinguish between IDA and TT. With a cut-off value of 23, the area under the curve (AUC) was 0.995 (95% CI of 0.99-1.00), the sensitivity was 97%, and the specificity was 99.1%.

CONCLUSIONS

The new RBC parameters on Beckman Coulter DxH800 provide useful information in distinguishing between IDA and TT, which is important for clinical decision-making and for streamlining laboratory testing. A new formula is devised that performs better than other discriminant functions in the literature.

The prevalence and molecular spectrum of α- and β-globin gene mutations in 14,332 families of Guangdong Province, China

OBJECTIVE

To reveal the familial prevalence and molecular variation of α- and β-globin gene mutations in Guangdong Province.

METHODS

A total of 40,808 blood samples from 14,332 families were obtained and analyzed for both hematological and molecular parameters.

RESULTS

A high prevalence of α- and β-globin gene mutations was found. Overall, 17.70% of pregnant women, 15.94% of their husbands, 16.03% of neonates, and 16.83% of couples (pregnant women and their husbands) were heterozygous carriers of α- or β-thalassemia. The regions with the highest prevalence were the mountainous and western regions, followed by the Pearl River Delta; the region with the lowest prevalence was Chaoshan. The total familial carrier rate (both spouses were α- or β-thalassemia carriers) was 1.87%, and the individual carrier rates of α- and β-thalassemia were 1.68% and 0.20%, respectively. The total rate of moderate-to-severe fetal thalassemia was 12.78% among couples in which both parents were carriers.

CONCLUSIONS

There was a high prevalence of α- and β-thalassemia in Guangdong Province. This study will contribute to the development of thalassemia prevention and control strategies in Guangdong Province.

Predicting future blood demand from thalassemia major patients in Hong Kong

Background

In Hong Kong, thalassemia major (TM) patients utilized up to 9.5% of blood supply in 2009. For long-term management of blood supply, we predicted the future blood demand of TM patients for the next 10 years.

Methods and Results

Annual individual transfusion data in 2005–2009 and demographic information of 381 TM patients were obtained from the Hong Kong Red Cross Blood Transfusion Service database. A generalized estimating equation (GEE) model was fitted to establish the potential relations of blood demand with age, sex, body weight, year of transfusion and splenectomy, accounted for within-patient correlation. The fitted model was used to predict future blood demand for the existing patients by accounting for expected change in body weight and mortality rate. We also predicted the number of new cases in the future based on age- and sex-specific TM incidence and official population projections. Future blood demand was predicted by combining blood demand from the existing and new patients. Female (RR = 0.94, p = 0.006) and history of splenectomy (RR = 0.85, p<0.001) were significantly associated with lower blood demand, while age and weight had an inverted U-shape relation with maximal blood demand at around 24 years of age and 71.8 kg, respectively. We predicted that the total blood demand would increase 0.81% annually from 13,459 units in 2009 to 15,183 units in 2024, with new TM cases accounting for 31.7% of the overall blood demand in 2024.

Conclusions

Our results showed that future annual blood demand from TM patients would steadily increase in the next 10 years. Reducing incidence of TM cases in the future (by improving public education, antenatal care, prenatal diagnosis) and minimizing blood use among existing TM cases (e.g. with hemopoietic stem cell transplantation) can help relieve the burden on management of future blood demand.

Prevalence and genetic analysis of α-thalassemia and β-thalassemia in Chongqing area of China

BACKGROUND AND AIMS

Thalassemia is one of the most common hereditary disorders. This study aimed to investigate the prevalence of thalassemia and the mutation spectrum in Chongqing, the southern area of China.

METHODS

A total of 1057 children were recruited from Chongqing. Hematological parameters were examined and globin genes were genetically analyzed.

RESULTS

The total frequency of thalassemia carriers was 7.76% in this group of children. Among these, α-thalassemia was 5.20%, β-thalassemia was 1.99% and abnormal hemoglobin variant was 0.57%. Furthermore, 24 cases of α-triplication were detected, frequency of which was 2.55%. The true prevalence of silent α-thalassemia was first reported in this study. In addition, six novel mutations that give rise to α-thalassemia and two rare abnormal hemoglobin variants were first identified in Chinese population.

CONCLUSIONS

Our data suggested that the population in Chongqing are at high risk of α- and β-thalassemia. The findings will be useful for genetic counseling and the prevention of severe thalassemias in this area.

Two unusual cases of haemoglobin Bart's hydrops fetalis due to uniparental disomy or non-paternity

The authors present 2 unusual cases of haemoglobin (Hb) Bart's hydrops fetalis and highlight the problem of a screening system for α-thalassaemia which focuses on maternal and paternal mean corpuscular volume (MCV) alone. Normal paternal MCV may not preclude fetal Hb Bart's disease because of the rare occurrence of maternal uniparental disomy or non-paternity. During a mid-trimester anomaly scan, with fetal cardiomegaly or hydrops in a woman with low MCV but normal paternal MCV, obstetricians should remain alert for fetal Hb Bart's disease. This is very important and relevant for national screening systems in South-East Asia, where a routine mid-trimester scan may not be available. A routine mid-trimester anomaly scan should therefore be implemented and in high prevalence areas, sonographers should be sensitive to the cardio-thoracic ratio even if screening shows that pregnancy is unlikely to be at risk.