Thalassemias and hemoglobinopathies in Turkey

An ESHG-ESHRE survey on the current practice of expanded carrier screening in medically assisted reproduction

STUDY QUESTION

What is the current practice and views on (expanded) carrier screening ((E)CS) among healthcare professionals in medically assisted reproductive (MAR) practices in Europe?

SUMMARY ANSWER

The findings show a limited support for ECS with less than half of the respondents affiliated to centres offering ECS, and substantial variation in practice between centres in Europe.

WHAT IS KNOWN ALREADY

The availability of next-generation sequencing, which enables testing for large groups of genes simultaneously, has facilitated the introduction and expansion of ECS strategies, currently offered particularly in the private sector in the context of assisted reproduction.

STUDY DESIGN, SIZE, DURATION

A cross-sectional survey evaluating practice and current views among professionals working in MAR practice in different European countries was designed using the online SurveyMonkey tool. The web-based questionnaire included questions on general information regarding the current practice of (E)CS in MAR and questions on what is offered, to whom the test is offered, and how it is offered. It consisted mostly of multiple-choice questions with comment boxes, but also included open questions on the respondents' attitudes/concerns relevant to (E)CS practice, and room to upload requested files (e.g. guidelines and gene panels). In total, 338 responses were collected from 8 February 2022 to 11 April 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The online survey was launched with an invitation email from the ESHRE central office (n = 4889 emails delivered) and the European Society of Human Genetics (ESHG) central office (n = 1790 emails delivered) sent to the ESHRE and ESHG members, and by social media posts. The survey was addressed to European MAR centres or gamete banks and to centres located in non-European countries participating in the European IVF-monitoring Consortium. Two reminder emails were sent. After exclusion of 39 incomplete responses received (e.g. only background information), 299 respondents from 40 different countries were included for analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, 42.5% (127/299) of respondents were affiliated to centres offering ECS. The perceived responsibility to enable prospective parents to make informed reproductive decisions and preventing suffering/burden for parents were the main reasons to offer ECS. A single ECS panel is offered by nearly 45% (39/87 received answers) of the centres offering ECS, 25.3% (22/87) of those centres offer a selection of ECS panels, and 29.9% (26/87) offer whole exome sequencing and a large in silico panel. Different ranges of panel sizes and conditions were included in the ECS panel(s) offered. Most of the respondents (81.8%; 72/88 received answers) indicated that the panels they offer are universal and target the entire population. Pathogenic variants (89.7%; 70/78 received answers), and to a lesser extent, likely pathogenic variants (64.1%%; 50/78 received answers), were included in the ECS report for individuals and couples undergoing MAR with their own gametes. According to 87.9% (80/91 received answers) of the respondents, patients have to pay to undergo an ECS test. Most respondents (76.2%; 61/80 received answers) reported that counselling is provided before and after the ECS test. Preimplantation genetic testing, the use of donor gametes, and prenatal diagnostic testing were the three main reproductive options discussed with identified carrier couples. The main reason, according to the respondents, for not offering ECS in their centre, was the lack of professional recommendations supporting ECS (52.5%; 73/139 received answers) and the high cost for couples or reimbursement not being available (49.6%; 69/139). The challenges and moral dilemmas encountered by the respondents revolved mainly around the content of the offer, including the variants classification and the heterogeneity of the panels, the counselling, and the cost of the test.

LIMITATIONS, REASONS FOR CAUTION

Although the total number of respondents was acceptable, the completion rate of the survey was suboptimal. In addition, the heterogeneity of answers to open-ended questions and the ambiguity of some of the answers, along with incomplete responses, posed a challenge in interpreting survey results. It is also plausible that some questions were not easily understood by the respondents. For this reason, response and non-response bias are acknowledged as further limitations of the survey.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this survey could aid in identifying potential challenges or areas for improvement in the current practice of ECS in the MAR field and contribute to the discussion on how to address them. The results underline the need to stimulate a more knowledge-based debate on the complexity and the pros and cons of a possible implementation of ECS in MAR.

STUDY FUNDING/COMPETING INTEREST(S)

All costs relating to the development process were covered from European Society of Human Reproduction and Embryology and European Society of Human Genetics funds. There was no external funding of the development process or manuscript production. A.C. is full-time employee of Juno Genetics. L.H. declared receiving a research grant during the past 36 months from the Netherlands Organisation for Health Research and Development. She has also participated in a Health Council report of the Netherlands on preconception carrier screening and collaborated with the VSOP Dutch Genetic Alliance (patient umbrella organization on rare and genetic disorders). L.H. and C.v.E. are affiliated with Amsterdam University Medical Centre, a hospital that offers ECS in a non-commercial setting. R.V. received honoraria for presentations from Merck Academy and is unpaid board member of the executive committee of the Spanish Fertility Society. The other authors had nothing to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Thalassemia patients in transfussion dependent period and after hematopoietic stem cell transplantation: how are the psychiatric status and life quality of these patients?

Although hematopoietic stem cell transplantation (HSCT) has been widely used to treat patients with beta-thalassemia major, evidence showing whether this treatment improves mental health, self esteem and health-related quality of life (HRQoL) is limited. We aimed to describe psychiatric problems, HRQoL and self-esteem scores of patients who have thalassemia and compared with patients who underwent HSCT in the current study. A total of 24 patients with thalassemia major and 13 patients who underwent HSCT at least 2 years ago aged between 7-37 years were included. We used The Children's Depression Inventory, The Spielberger State-Trait Anxiety Inventory, and Pediatric Quality of LifeTM (PedsQL™) for assesment of children and Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), World Health Organization Quality of Life Scale Brief Version (WHOQOL-BREF) for assessment of adults. We also used Piers Harris Self Concept Scale for children and adults. Psychopathologies are common in both groups (50% in Thalassemia group and 69.2% in HSCT group). Popularity scores in Piers Haris scale of patients in HSCT group were significantly higher compared to thalassemia group (p = 0.03). Additionally, HSCT group had higher scores in physical health subscales of HRQoL in both children and parents'(p = 0.02, p = 0.03 respectively). Our findings suggest improved HRQoL and self-esteem in thalassemia patients after HSCT. However, due to the high prevalence of mental disorders in both groups, we would like to emphasize that clinicians should examine not only the physical but also the psychological state of the patients with thalessemia during the their treatment and follow-up period after HSCT.

Interventions addressing genetic disease burdens within selected countries in the MENA region: a scoping review

BACKGROUND

The MENA region is disproportionately affected by genetic disease. The aim of this research is to scope the region for evidence of genetic services and public health interventions to identify geographic gaps, and to provide a descriptive overview of interventions to identify knowledge gaps.

METHODS

This study is conducted as a scoping review and follows the Arksey & O'Malley scoping review framework.

RESULTS

Seventy-six articles spanning 16 MENA nations met inclusion criteria. Studies included interventions in the form of genetic service provision (n=28), as well as comprehensive programs including pilot programs (n=7), community-based genetics programs (n=6) national-level prevention programs (n=18), and national-level mandatory programs (n=17).

CONCLUSIONS

There is an imbalanced response to genetic disease burdens across the MENA region. More research is warranted where interventions are scarce, particularly to inform development of pilot community-based programs. There is also a need for better monitoring and evaluation of existing nation-wide programs.

Awareness Among Educated and Uneducated Parents of Beta-Thalassemia Major Patients About Antenatal Screening

Objective: This study aims to determine the awareness among educated and uneducated parents of beta-thalassemia major patients about antenatal screening.

Setting: The study was conducted by the Lady Reading Hospital Medical Teaching Institution (MTI), Peshawar.

Duration of the study: This study was conducted for six months.

Materials and methods: A total of 296 parents of beta-thalassemia major were interviewed. Parents who were not ready to give consent and other hemolytic anemia patients were excluded. Data were collected on self-structure pretested Performa. The demography of the patients and awareness of the parents regarding antenatal screening were recorded from each participant. A chi-squared test was used to assess the association between parental education and antenatal screening. A p-value of less than 0.05 was considered significant.

Results: A total of 296 patients were studied; 160 were males (54.1%), and 136 were females (45.9%). The mean age was 6.84 years. Mothers (74.3%) accompanied majority of the patients. Most of the parents (265; 89.5%) were uneducated, and 80% of the parents were not aware of any antenatal screening.

Conclusion: There was a significant association between the education of parents and awareness of antenatal screening (p = 0.01).

Dynamic Thiol-Disulfide Homeostasis in Children With β-Thalassemia Trait

In children with β-thalassemia (β-thal) trait, tissue damage occurs with oxidative stress due to oxygen free radicals and reactive oxygen species (ROS) production. Dynamic thiol-disulfide homeostasis (DTDH) is one of the most important indicators showing the pro-oxidant/antioxidant status in the body. In this study, we aimed to examine the status of DTDH by measuring native thiol, disulfide, and total thiol levels in children with β-thal trait. The study included 40 children with β-thal trait and 30 healthy controls (matched by age and gender). The DTDH parameters were measured by an automated method and results were compared between the groups. The levels of native thiol, total thiol, and disulfide in children with β-thal trait group were statistically significantly higher than the control group (p < 0.001). There was no significant difference in disulfide/native thiol, disulfide/total thiol, and native thiol/total thiol levels between the groups. In addition, there was no correlation between hemoglobin (Hb) and serum ferritin levels with the markers of DTDH in children with β-thal trait. In our study, a significant increase was found in native thiol, total thiol, and disulfide levels in response to oxidative stress in children with β-thal trait compared to the healthy control group. Disulfide levels of the children with β-thal trait were higher than the control group, showing oxidative stress is high in β-thal trait. Accordingly, it increases the native thiol and total thiol capacity as compensation.

β-Globin Gene Mutations in Pediatric Patients with β-Thalassemia in the Region of Çukurova, Turkey

β-Thalassemia (β-thal) is one of the most common genetic disorders in Turkey. In this study, we investigated the mutations and frequency of β-thal at the molecular level in pediatric β-thal patients in the Çukurova region. The β-thal mutations of 52 cases were analyzed. An automated blood cell counter was used for hematological data. Cellulose acetate electrophoresis and high performance liquid chromatography (HPLC) methods were used for hemoglobin (Hb) typing. Amplification refractory mutation system (ARMS), restriction fragment length polymorphism (RFLP), gap-polymerase chain reaction (gap-PCR) and DNA sequencing analysis methods were used to determine genomic features. In this study, we found that 36 subjects carried homozygous mutations [IVS-I-110 (G>A) (HBB: c.93-21G>A) (58.3%), codon 8 (-AA) (HBB: c.25_26delAA) (5.6%), -30 (T>A) (HBB: c.-80T>A) (5.6%), IVS-I-6 (T>C) (HBB: c.92+6T>C) (5.6%) and IVS-II-1 (G>A) (HBB: c.315+1G>A) (5.6%)]. We found that 13 subjects carried compound heterozygosities for IVS-I-110/IVS-I-6 (15.4%) and IVS-I-110/frameshift codon (FSC) 44 (-C) (HBB: c.135delC) (15.4%). We observed that the Syrian subject also carried a compound heterozygosity for IVS-I-6/IVS-I-25 (-25 bp) (HBB: c.93_21del). We determined that the most frequently observed β-thal mutation in the Çukurova region, where various types of hemoglobinopathies have been observed, is the IVS-I-110 mutation. As the prevalence of the disease will affect the region where the immigrant population is dense, population screening and prenatal diagnosis (PND) should be increased and the public should be made aware of the consequences.

Development of gene editing strategies for human β-globin (HBB) gene mutations

Recent developments in gene editing technology have enabled scientists to modify DNA sequence by using engineered endonucleases. These gene editing tools are promising candidates for clinical applications, especially for treatment of inherited disorders like sickle cell disease (SCD). SCD is caused by a point mutation in human β-globin gene (HBB). Clinical strategies have demonstrated substantial success, however there is not any permanent cure for SCD available. CRISPR/Cas9 platform uses a single endonuclease and a single guide RNA (gRNA) to induce sequence-specific DNA double strand break (DSB). When this accompanies a repair template, it allows repairing the mutated gene. In this study, it was aimed to target HBB gene via CRISPR/Cas9 genome editing tool to introduce nucleotide alterations for efficient genome editing and correction of point mutations causing SCD in human cell line, by Homology Directed Repair (HDR). We have achieved to induce target specific nucleotide changes on HBB gene in the locus of mutation causing SCD. The effect of on-target activity of bone fide standard gRNA and newly developed longer gRNA were examined. It is observed that longer gRNA has higher affinity to target DNA while having the same performance for targeting and Cas9 induced DSBs. HDR mechanism was triggered by co-delivery of donor DNA repair templates in circular plasmid form. In conclusion, we have suggested methodological pipeline for efficient targeting with higher affinity to target DNA and generating desired modifications on HBB gene.

Effect of hemoglobin F and A2 on hemoglobin A1c determined by cation exchange high-performance liquid chromatography

Background

The potential effect of increase in hemoglobin (Hb) A2 and HbF on glycated hemoglobin (HbA1c) measurements were investigated using a high-performance liquid chromatography (HPLC) method compared with an immunoturbimetric assay.

Methods

Samples producing abnormal chromatograms during the measurement of routine HbA1c testing with HPLC were further analyzed to characterize abnormal Hb variants. Patients were divided into three groups that had only high HbF (group 1), only high HbA2 (group 2), and both high HbA2 and HbF (group 3). HbA1c values of patients were re-assayed using the immunoturbidimetric method (Advia, Siemens Healthcare, Germany).

Results

HbA1c levels were significantly higher in all groups measured by immunoassay than in HPLC. We found a positive correlation between HPLC and immunoturbidimetry in the group 2 and a slight correlation in the group 1. There was no correlation between the two methods in group 3.

Conclusions

HbA1c measurement by HPLC method interfering with elevated HbA2 and HbF, especially HbF, should be verified by an immunoturbidimetric method.

Causes of Hypochromic Microcytic Anemia in Children and Evaluation of Laboratory Parameters in the Differentiation

Most common causes of microcytic anemia in children are iron deficiency anemia (IDA) and thalassemia. Differentiation of these and detection of coexistence is essential for genetic counseling and to set a treatment plan. Aim is to characterize the frequency of IDA and thalassemia trait (TT) in children presenting with hypochromic, microcytic anemia and to define the significance of blood count parameters in differential diagnosis. Of the 200 enrolled, 107 were male (53.5%). In total 154 had IDA (77%), 27 had β-TT (13.5%), and in 11 (5.5%) both conditions coexisted. Eight patients had α-thalassemia gene mutations, 3 of these also had IDA. RBC, MCV, Mentzer index, serum iron, TIBC, ferritin were significantly different between IDA and β-TT patients (P<0.001); however, RDW was not different between the 2 groups (P>0.05). Sensitivity and specificity of Mentzer index for the detection of β-TT were 100% and 69.4%, respectively. The positive and negative predictive values of Mentzer index in diagnosing β-TT were 36.6% and 100%, respectively. Differential diagnosis of microcytic anemia is important in children, especially in regions where IDA and thalassemia are both prevalent. We found that 7% of children referred to our clinic for hypochromic, microcytic anemia had both TT and IDA. Our data showed that serum iron, ferritin, TIBC, MCV, and Mentzer index were all valuable markers in diagnosing IDA and were significantly different compared with β-TT patients; RDW was not different between the 2 groups.

Heterozygous Beta Chain Variant Hemoglobin Pusan: A Rare Case Report in Turkish Population

The case, detected during routine thalassemia (hemoglobin variant) screening, was a 25-year-old male patient of Turkish origin. Physical examination revealed no abnormal findings. Laboratory findings did not reveal any signs of anemia (iron deficiency, B12 deficiency, etc.). However, when the hemoglobin variant report was being evaluated, it was found that besides the normal hemoglobin peaks, there was another peak that had not been defined before. The sample was sent to genetic analysis for verification with the suspicion of an unknown hemoglobin variant. According to the genetic analysis, the unknown hemoglobin variant was found to be Hemoglobin Pusan (Hb Pusan). The aim of this study is to give information about a hemoglobin variant which is rarely seen in Turkish population and to raise awareness about this hemoglobin variant. In addition, clinical and hematological findings of this disease are discussed in the case report.

A Novel Technique of Spectral Discrimination of Variants of Sickle Cell Anemia

Sickle cell anemia (SCA) is an inherited blood disorder with worldwide incidence of 15%; out of this, it is found in up to 20% in countries like Kingdom of Saudi Arabia and Bahrain. The standard conventional method of detection is complete blood count (CBC) followed by hemoglobin electrophoresis or high-performance liquid chromatography (HPLC) or both. In this context, spectral detection of variants of sickle cell anemia (SCA) is an innovative technique, which when made accurate and reliable could be an effective alternative, since the instrumentation is compact (5 kg) and hence portable. This makes mass screening even in remote villages possible. In this paper, we give the essential aspects of fluorescent spectral features of sickle cell trait (SCT), sickle cell disease (SCD), beta (β) thalassemia trait (BTT) + SCD, and beta (β) thalassemia disease (BTD) + SCD. All the above four major variants could be discriminated among themselves and also from the normal control blood sample. All these analyses could be carried out with 5 ml of blood, in a time period of 10 minutes. The results of this paper give strong support for an alternative method, a spectral technique, for molecular-level diagnosis of sickle cell anemia and other closely related blood disorders.

Organ damage mitigation with the Baskent Sickle Cell Medical Care Development Program (BASCARE)

The Eastern Mediterranean is among the regions where sickle cell disease (SCD) is common. The morbidity and mortality of this disease can be postponed to adulthood through therapies implemented in childhood. The present study focuses on the organ damage-reducing effects of the Baskent Sickle Cell Medical Care Development Program (BASCARE), which was developed by a team who lives in this region and has approximately 25 years of experience. The deliverables of the program included the development of an electronic health recording system (PRANA) and electronic vaccination system; the use of low citrate infusion in routine prophylactic automatic erythrocyte exchange (ARCE) programs including pregnant women; the use of leukocyte-filtered and irradiated blood for transfusion; the use of magnetic resonance imaging methods (T2) for the management of transfusion-related hemosiderosis; and the implementation of an allogeneic hematopoietic stem cell transplantation protocol for adult patients. The sample was composed of 376 study subjects and 249 control subjects. The hospital's Data Management System and the central population operating system were used for data collection. BASCARE enabled better analysis and interpretation of complication and mortality data. Vaccination rates against influenza and pneumococcal disease improved (21.5% vs 50.8% and 21.5% vs 49.2%, respectively). Effective and safe ARCE with low citrate infusion were maintained in 352 subjects (1003 procedures). Maternal and fetal mortality was prevented in 35 consecutive pregnant patients with ARCE. Chelating therapy rates reduced from 6.7% to 5%. Successful outcomes could be obtained in all 13 adult patients who underwent allogeneic peripheral stem cell transplantation from a fully matched, related donor. No patients died by day 100 or after the first year. Cure could be achieved without graft loss, grades III to IV acute graft versus host disease, extensive chronic graft versus host disease, or other major complications. The BASCARE program significantly improved patient care and thereby prolonged the life span of SCD patients (42 ± 13 years vs 29 ± 7 years, P < .001). We may recommend using such individualized programs in centers that provide health care for patients with SCD, in accordance with holistic approach due to the benign nature but malignant course of the disease.

A National Registry of Thalassemia in Turkey: Demographic and Disease Characteristics of Patients, Achievements, and Challenges in Prevention

Objective:

The Turkish Society of Pediatric Hematology set up a National Hemoglobinopathy Registry to demonstrate the demographic and disease characteristics of patients and assess the efficacy of a hemoglobinopathy control program (HCP) over 10 years in Turkey.

Materials and Methods:

A total of 2046 patients from 27 thalassemia centers were registered, of which 1988 were eligible for analysis. This cohort mainly comprised patients with β-thalassemia major (n=1658, 83.4%) and intermedia (n=215, 10.8%).

Results:

The majority of patients were from the coastal areas of Turkey. The high number of patients in Southeastern Anatolia was due to that area having the highest rates of consanguineous marriage and fertility. The most common 11 mutations represented 90% of all β-thalassemia alleles and 47% of those were IVS1-110(G->A) mutations. The probability of undergoing splenectomy within the first 10 years of life was 20%, a rate unchanged since the 1980s. Iron chelators were administered as monotherapy regimens in 95% of patients and deferasirox was prescribed in 81.3% of those cases. Deferasirox administration was the highest (93.6%) in patients aged <10 years. Of the thalassemia major patients, 5.8% had match-related hemopoietic stem cell transplantation with a success rate of 77%. Cardiac disease was detected as a major cause of death and did not show a decreasing trend in 5-year cohorts since 1999.

Conclusion:

While the HCP has been implemented since 2003, the affected births have shown a consistent decrease only after 2009, being at lowest 34 cases per year. This program failure resulted from a lack of premarital screening in the majority of cases. Additional problems were unawareness of the risk and misinformation of the at-risk couples. In addition, prenatal diagnosis was either not offered to or was not accepted by the at-risk families. This study indicated that a continuous effort is needed for optimizing the management of thalassemia and the development of strategies is essential for further achievements in the HCP in Turkey.

β-Thalassemia Distribution in the Old World: an Ancient Disease Seen from a Historical Standpoint

Background

Haemoglobinopathies constitute the commonest recessive monogenic disorders worldwide, and the treatment of affected individuals presents a substantial global disease burden. β-thalassaemia is characterised by the reduced synthesis (β⁺) or absence (β^o) of the β-globin chains in the HbA molecule, resulting in accumulation of excess unbound α-globin chains that precipitate in erythroid precursors in the bone marrow and in the mature erythrocytes, leading to ineffective erythropoiesis and peripheral haemolysis. Approximately 1.5% of the global population are heterozygotes (carriers) of the β-thalassemias; there is a high incidence in populations from the Mediterranean basin, throughout the Middle East, the Indian subcontinent, Southeast Asia, and Melanesia to the Pacific Islands.

Aim

The principal aim of this paper is to review, from a historical standpoint, our knowledge about an ancient disease, the β-thalassemias, and in particular, when, how and in what way β-thalassemia spread worldwide to reach such high incidences in certain populations.

Results

Mutations involving the β-globin gene are the most common cause of genetic disorders in humans. To date, more than 350 β-thalassaemia mutations have been reported. Considering the current distribution of β- thalassemia, the wide diversity of mutations and the small number of specific mutations in individual populations, it seems unlikely that β-thalassemia originated in a single place and time.

Conclusions

Various processes are known to determine the frequency of genetic disease in human populations. However, it is almost impossible to decide to what extent each process is responsible for the presence of a particular genetic disease. The wide spectrum of β-thalassemia mutations could well be explained by looking at their geographical distribution, the history of malaria, wars, invasions, mass migrations, consanguinity, and settlements. An analysis of the distribution of the molecular spectrum of haemoglobinopathies allows for the development and improvement of diagnostic tests and management of these disorders.

Invasive prenatal diagnosis of fetal thalassemia

Thalassemia is the most common monogenic inherited disease worldwide, affecting individuals originating from many countries to various extents. As the disease requires long-term care, prevention of the homozygous state presents a substantial global disease burden. The comprehensively preventive programs involve carrier detections, molecular diagnostics, genetic counseling, and prenatal diagnosis. Invasive prenatal diagnosis refers to obtaining fetal material by chorionic villus sampling (CVS) at the first trimester, and by amniocentesis or cordocentesis at the second trimester. Molecular diagnosis, which includes multiple techniques that are aimed at the detection of mutations in the α- or β-globin genes, facilitates prenatal diagnosis and definitive diagnosis of the fetus. These are valuable procedures for couples at risk, so that they can be offered options to have healthy offspring. According to local practices and legislation, genetic counseling should accompany the invasive diagnostic procedures, DNA testing, and disclosure of the results. The most critical issue in any type of prenatal molecular testing is maternal cell contamination (MCC), especially when a fetus is found to inherit a particular mutation from the mother. The best practice is to perform MCC studies on all prenatal samples. The recent successful studies of fetal DNA in maternal plasma may allow future prenatal testing that is non-invasive for the fetus and result in significant reduction of invasive diagnostic procedures.

Hemoglobinopathies in the Çukurova Region and Neighboring Provinces

To contribute to the creation of a mutation map of the region, we aimed to determine the mutation spectrum of thalassemias and abnormal hemoglobins (Hbs) in the Çukurova region and surrounding provinces. In this study, a total of 8135 samples from Adana, Hatay, Mersin, Konya and Kayseri provinces between 1993 and 2014 were analyzed. Complete blood cell (CBC) counts and Hb typing were carried out using automatic cell counters, cellulose acetate membrane electrophoresis and high performance liquid chromatography (HPLC), respectively. For the molecular analyses, genomic DNA was extracted using both manual and automated DNA extraction devices. Determination of Hb mutations were done by microarray, restriction fragment length polymorphism (RFLP), amplification refractory mutation system (ARMS) and gap-polymerase chain reaction (gap-PCR) methodologies. Samples were analyzed for abnormal Hb and thalassemia mutations. Out of 8135 samples, 1382 were observed to be carrying Hb mutations. It was identified that 826 mutation carriers included abnormal Hbs with a frequency of 59.7%, 416 carriers included β-thalassemia (β-thal) mutations with a frequency of 30.7% and 136 carriers included α-thalassemia (α-thal) mutations with a frequency of 9.9%. In this study, the most frequently observed abnormal Hb in the region was Hb S [β6(A3)Glu→Val (GTG > GAG), HBB: c.20T > A], whereas the most commonly observed mutations were the IVS-I-110 (G > A) (HBB: c.93-21G > A) point mutation in β-thal and the 3.7 kb deletion in α-thal.

Observed and expected frequencies of structural hemoglobin variants in newborn screening surveys in Africa and the Middle East: deviations from Hardy-Weinberg equilibrium

PURPOSE

Our objective was to compare observed and expected genotype proportions from newborn screening surveys of structural hemoglobin variants.

METHODS

We conducted a systematic review of newborn screening surveys of hemoglobins S and C in Africa and the Middle East. We compared observed frequencies to those expected assuming Hardy-Weinberg equilibrium (HWE). Significant deviations were identified by an exact test. The fixation index FIS was calculated to assess excess homozygosity. We compared newborn estimates corrected and uncorrected for HWE deviations using demographic data.

RESULTS

Sixty samples reported genotype counts for hemoglobin variants in Africa and the Middle East. Observed and expected counts matched in 27%. The observed number of sickle cell anemia (SCA) individuals was higher than expected in 42 samples, reaching significance (P < 0.05) in 24. High FIS values were common across the study regions. The estimated total number of newborns with SCA, corrected based on FIS, was 33,261 annual births instead of 24,958 for the 38 samples across sub-Saharan Africa and 1,109 annual births instead of 578 for 12 samples from the Middle East.

CONCLUSION

Differences between observed and expected genotype frequencies are common in surveys of hemoglobin variants in the study regions. Further research is required to identify and quantify factors responsible for such deviations. Estimates based on HWE might substantially underestimate the annual number of SCA-affected newborns (up to one-third in sub-Saharan Africa and one-half in the Middle East).