Antenatal screening for haemoglobinopathies: current status, barriers and ethics

Sickle Cell Disease

Background

Sickle cell disease (SCD) is among the most frequent hereditary disorders globally and its prevalence in Europe is increasing due to migration movements.

Summary

The basic pathophysiological event of SCD is polymerization of deoxygenated sickle hemoglobin, resulting in hemolysis, vasoocclusion, and multiorgan damage. While the pathophysiological cascade offers numerous targets for treatment, currently only two disease-modifying drugs have been approved in Europe and transfusion remains a mainstay of both preventing and treating severe complications of SCD. Allogeneic stem cell transplantation and gene therapy offer a curative option but are restricted to few patients due to costs and limited availability of donors.

Key Message

Further efforts are needed to grant patients access to approved treatments, to explore drug combinations and to establish new treatment options.

Incidence Trends of Inherited Anemias at the Global, Regional, and National Levels Over Three Decades

Inherited anemia continues to pose a significant public health concern on a global scale, owing to its extensive geographical prevalence, substantial patient population, and profound ramifications. Here, we investigated detailed information on inherited anemias (including thalassemias, thalassemias trait, sickle cell disease, sickle cell trait, G6PD deficiency, and G6PD trait) for the period 1990-2019 from the Global Burden of Disease study. Over the course of three decades, there has been a persistent rise in the incidence of inherited anemias worldwide, culminating in a total of 44,896,026 incident cases in 2019. However, the prevalence of inherited anemias has exhibited a consistent downward trend over successive years. Significantly, these inherited anemias primarily impact females, exhibiting a male-to-female ratio of 1:1.88. Among males, the most prevalent inherited anemia is G6PD deficiency, whereas G6PD trait prevails among females. The incidence rates of inherited anemias and their temporal trend exhibited significant variations across different regions, with Central Sub-Saharan Africa displaying the highest incidence rates and Central Latin America experiencing the most substantial decline. The findings of this study suggest a significant correlation between the Socio-Demographic index (SDI) and incidence rates of inherited anemias, particularly in regions with lower SDI levels such as Africa and South Asia. These results contribute valuable insights for the analysis of global trends in the burden of inherited anemias.

The Danish national haemoglobinopathy screening programme: Report from 16 years of screening in a low-prevalence, non-endemic region

The Danish national haemoglobinopathy screening programme seeks to determine parental haemoglobinopathy carrier state antenatally. In this retrospective register-based study, we evaluated the 16-year trajectory of this programme, utilising the Danish Red Blood Cell Centre's laboratory database, covering approximately 77% of the Danish population. During the study period, we observed a substantial increase in annual diagnostic examinations performed, from 389 in 2007 to 3030 in 2022. Women constituted 88% of these cases, aligning with the emphasis of the screening programme. Of these, 54% of women of reproductive age (15-40 years) and 10% of women >40 years were specified as pregnant. During our study period, 61 children were born with a severe haemoglobinopathy, out of which 23 children were born from mothers not residing in Denmark during their first trimester thus not included in the screening programme. Prenatal invasive testing was performed for 60 fetuses, identifying 12 with homozygous or compound heterozygous haemoglobinopathy. The Danish haemoglobinopathy screening programme has provided screening, information and reproductive choices for numerous families. During the study period, screening for haemoglobinopathies has been steadily increasing and is expected to continue to increase. Awareness of and adherence to the screening programme is subject of further investigation and optimisation.

Prospects for Expansion of Universal Newborn Screening in Bulgaria: A Survey among Medical Professionals

Determining the scope of a newborn screening program is a challenging health policy issue. Our study aimed to explore the attitudes of specialists in pediatrics, neonatology, medical genetics, and biochemistry regarding the prospects for expanding the panel of diseases for universal newborn screening in Bulgaria. We conducted an online survey in March-May 2022. The questionnaire listed 35 disorders that could potentially be included in the Bulgarian panel for universal newborn screening. If endorsing a specific condition, participants had to justify their position by judging its performance against the ten principles of Wilson and Jungner. We found a high degree of knowledge about the current universal newborn screening program in Bulgaria. An overwhelming majority (97.4%) supported the expansion of the panel to include more conditions. Four disorders obtained more than 50% approval for inclusion: cystic fibrosis (87.0%), thalassemia (72.7%), spinal muscular atrophy (65.6%), and classical galactosemia (59.1%). The perception of the condition as an important health problem was the most significant factor in this support. The costs of diagnosis and treatment appeared to be the main source of concern. We recommend country-specific economic evaluations and research on the views of other stakeholders, including the government, payers, and patient organizations, to better understand and manage the complex nature of newborn screening policymaking.

Defining global strategies to improve outcomes in sickle cell disease: a Lancet Haematology Commission

All over the world, people with sickle cell disease (an inherited condition) have premature deaths and preventable severe chronic complications, which considerably affect their quality of life, career progression, and financial status. In addition, these people are often affected by stigmatisation or structural racism, which can contribute to stress and poor mental health. Inequalities affecting people with sickle cell disease are also reflected in the distribution of the disease—mainly in sub-Saharan Africa, India, and the Caribbean—whereas interventions, clinical trials, and funding are mostly available in North America, Europe, and the Middle East. Although some of these characteristics also affect people with other genetic diseases, the fate of people with sickle cell disease seems to be particularly unfair. Simple, effective interventions to reduce the mortality and morbidity associated with sickle cell disease are available. The main obstacle preventing better outcomes in this condition, which is a neglected disease, is associated with inequalities impacting the patient populations. The aim of this Commission is to highlight the problems associated with sickle cell disease and to identify achievable goals to improve outcomes both in the short and long term.

The ambition for the management of people with sickle cell disease is that curative treatments become available to every person with the condition. Although this would have seemed unrealistic a decade ago, developments in gene therapy make this potentially achievable, albeit in the distant future. Until these curative technologies are fully developed and become widely available, health-care professionals (with the support of policy makers, funders, etc) should make sure that a minimum standard of care (including screening, prophylaxis against infection, acute medical care, safe blood transfusion, and hydroxyurea) is available to all patients.

In considering what needs to be achieved to reduce the global burden of sickle cell disease and improve the quality of life of patients, this Commission focuses on five key areas: the epidemiology of sickle cell disease (Section 1 ); screening and prevention (Section 2 ); established and emerging treatments for the management of the disease (Section 3 ); cellular therapies with curative potential (Section 4 ); and training and education needs (Section 5 ). As clinicians, researchers, and patients, our objective to reduce the global burden of sickle cell disease aligns with wider public health aims to reduce inequalities, improve health for all, and develop personalised treatment options. We have observed in the past few years some long-awaited momentum following the development of innovative point-of-care testing devices, new approved drugs, and emerging curative options. Reducing the burden of sickle cell disease will require substantial financial and political commitment, but it will impact the lives of millions of patients and families worldwide and the lessons learned in achieving this goal would unarguably benefit society as a whole.

Additional value of red blood cell parameters in predicting uncommon α-thalassemia; experience from 10 years of α-globin gene sequencing and copy number variation analysis

INTRODUCTION

The diagnosis of rare forms of α-thalassemia requires laborious genetic analyses. Accurate sample selection for such evaluation is therefore essential. The main objectives of this study were to investigate the predictive power of red blood cell parameters to detect rare forms of α-thalassemia (substudy 1), and to explore the frequency of rare versus common forms of α-thalassemia in our sample population (substudy 2).

METHODS

In substudy 1, we reviewed all blood samples selected for extended α-hemoglobinopathy evaluation at our laboratory during 2011-2020 (n = 1217), which included DNA sequencing and/or copy number variation analysis. We assessed α-thalassemia positive samples at different levels of mean corpuscular hemoglobin (MCH) alone and in combination with results for red blood cell count (RBC) or red cell distribution width (RDW). In substudy 2, we examined the distribution of α-thalassemia genotypes for all samples submitted to a first-tier hemoglobinopathy evaluation at our laboratory during 2014-2020 (n = 6495).

RESULTS

In substudy 1, both RBC and RDW added predictive value in detecting rare forms of α-thalassemia in samples from adults and children. In adult samples with MCH ≤ 23 pg, the presence of erythrocytosis increased the detection rate from 27% to 74% as compared to non-erythrocytosis, while normal RDW increased the detection rate from 36% to 86% as compared to elevated RDW. In substudy 2, rare forms of α-thalassemia were detected in 12% of α-thalassemia positive samples.

CONCLUSION

Initial assessment of MCH, RBC, and RDW provided valuable predictive information about the presence of rare forms of α-thalassemia during hemoglobinopathy evaluation.

The diagnosis and molecular analysis of a novel 27.2 kb deletion causing α0-thalassemia

BACKGROUND

Thalassemia, one of the most prevalent monogenic diseases worldwide, is caused by an imbalance of α-like and non-α-like globin chain production. Copy number variations, which cause the most common genotype of α-thalassemia, can be detected by multiple diagnostic methods.

CASE REPORT

The proband was a 31-year-old female who was diagnosed with microcytic hypochromic anemia by antenatal screening. Hematological analysis and molecular genotyping were conducted on the proband and the proband's family members. Gap-polymerase chain reaction, Sanger sequencing, multiplex ligation-dependent probe amplification, and next-generation sequencing were used to detect potentially pathogenic genes. Familial studies and genetic analyses revealed a novel deletion of 27.2 kb located in the α-globin gene cluster (NC_000016.9: g. 204538_231777delinsTAACA).

CONCLUSIONS

We reported a novel α-thalassemia deletion and described the process of molecular diagnosis. The novel deletion extends the thalassemia mutation spectrum, which may be helpful in genetic counseling and clinical diagnosis in the future.

Hemoglobinopathy Patterns in Anemic Patients with a Strong History of Sickle Cell Disease in Eastern Province, Saudi Arabia: A Cross-Sectional Study

<b>Background and Objective:</b> The most common genetic disease in humans is hemoglobinopathies, also known as hemoglobin hereditary diseases. The purpose of this study was to look at the hemoglobinopathy patterns in anemic patients with a history of sickle cell disease in Saudi Arabia's Eastern Province. <b>Materials and Methods:</b> This prospective cross-sectional study was conducted on anemic patients attending the hospital with a strong family history of hemoglobinopathy and general signs and symptoms, as well as mild to moderate anemia crises. One hundred and ten people were chosen to participate in this study. The research was carried out between September, 2019 and October, 2020. <b>Results:</b> The sickle cell trait was the most common hemoglobinopathy in males (31.1%) and sickle cell trait+beta thalassemia minor was the most common in females (18%). The gender of patients and the distribution of hemoglobinopathy types were found to have a significant relationship (p-value of 0.001). <b>Conclusion:</b> A significant correlation was discovered between the gender of patients and the distribution of hemoglobinopathy types. More efforts must be made to raise the prevention of endogamy awareness among Saudis.

MALDI-TOF-MS for Rapid Screening and Typing of β-Globin Variant and β-Thalassemia through Direct Measurements of Intact Globin Chains

BACKGROUND

Traditional phenotype-based screening for β-globin variant and β-thalassemia using hematological parameters is time-consuming with low-resolution detection. Development of a MALDI-TOF-MS assay using alternative markers is needed.

METHODS

We constructed a MALDI-TOF-MS-based approach for identifying various β-globin disorders and classifying thalassemia major (TM) and thalassemia intermedia (TI) patients using 901 training samples with known HBB/HBA genotypes. We then validated the accuracy of population screening and clinical classification in 2 separate cohorts consisting of 16 172 participants and 201 β-thalassemia patients. Traditional methods were used as controls. Genetic tests were considered the gold standard for testing positive specimens.

RESULTS

We established a prediction model for identifying different forms of β-globin disorders in a single MALDI-TOF-MS test based on δ- to β-globin, γ- to α-globin, γ- to β-globin ratios, and/or the abnormal globin-chain patterns. Our validation study yielded comparable results of clinical specificity (99.89% vs 99.71%), and accuracy (99.78% vs 99.16%) between the new assay and traditional methods but higher clinical sensitivity for the new method (97.52% vs 88.01%). The new assay identified 22 additional abnormal hemoglobins in 69 individuals including 9 novel ones, and accurately screened for 9 carriers of deletional hereditary persistence of fetal hemoglobin or δβ-thalassemia. TM and TI were well classified in 178 samples out of 201 β-thalassemia patients.

CONCLUSIONS

MALDI-TOF-MS is a highly accurate, predictive tool that could be suitable for large-scale screening and clinical classification of β-globin disorders.

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.

Maternal mortality among women with sickle cell disease in Jamaica over two decades (1998-2017)

BACKGROUND

Sickle cell disease (SCD) affects 2.8% of Jamaican antenatal women. Between 1998-2007 their maternal mortality ratio was 7-11 times higher than women without these disorders. We aim to determine if outcomes improved between 2008 and 17 amid declining fertility and changes in referral obstetric care.

METHODS

Maternal deaths in Jamaica's maternal mortality surveillance database (assembled since 1998) with SCD reported as underlying or associated cause of death were compared to those without known SCD, over two decades from 1998 to 2017. Social, demographic and health service variables were analysed using SPSS and EpiInfo Open.

FINDINGS

Over the two decades from 1998 to 2017, 806 (74%) of the 1082 pregnancy-associated deaths documented by the Jamaican Ministry of Health and Wellness were maternal deaths. The maternal mortality ratio (MMR) did not statistically change over the two periods for women with (p = 0.502) and without SCD (p = 0.629). The MMR among women with and without SCD in 2008-17 was 378.1 (n = 41) and 89.2/100,000 live births (n = 336) respectively, an odds ratio of 4.24 (95% CI: 3.07-5.87). When deaths due to their blood disorders were excluded, risk remained elevated at 2.17 (95% CI: 1.36-3.32). There was an upward trend in direct deaths over the two decades (p [trend]=0.051).

INTERPRETATION

MMRs were unchanged over two decades for Jamaicans with SCD. The high contribution to maternal mortality by women with SCD may explain some of the persistently higher mortality experience of women in the African diaspora. Multi-disciplinary evidence-based strategies need to be developed and tested which improve survival for women with SCD who want to have children.

FUNDING

No external funding was provided.

Evaluation of intervention strategy of thalassemia for couples of childbearing ages in Centre of Southern China

BACKGROUND

To describe the free intervention strategy of thalassemia for childbearing couples in Guangzhou.

METHODS

Routine hematology examinations were conducted for 137,222 couples. Among them, 37,501 couples who had mean corpuscular volume (MCV) <82 fL or mean corpuscular hemoglobin <27 pg were elected for Hb analysis and the deletions of four common α-thalassemia mutation. Reverse dot blot for common nondeletional α-thalassemia and β-thalassemia was selectively used. Three thousand twenty-two couples randomly selected were offered all those tests as a control group. Sanger sequencing, multiplex ligation-dependent probe amplification and next-generation sequencing were used for rare thalassemia. High-risk couples were offered prenatal diagnosis at 10-13 weeks' gestation based on informed consent.

RESULTS

The carrier rates of α-, β-, and αβ-thalassemia and δβ thalassemia/deletional HPFH were 7.7%, 3.02%, 0.5% and 0.059% respectively. Of them, 1.37% were identified as at-risk couples and 345 couples terminated the pregnancy. No severe α- and β-thalassemia births were observed. In the control group, two β- thalassemia carriers and one case with -α^3.7 /αα^QS were misdiagnosed, but all at-risk couples were found, and we could save 1,523,774 ¥ using our strategy. The cut-off points of 73.46 fL and 23.25 pg would be useful to find -α⁺ /α^T thalassemia.

CONCLUSION

The intervention strategy was cost-effective and offered reference in population thalassemia screening.