Ethnicity-Based Carrier Screening

Accepting or declining preconception expanded carrier screening: An exploratory study with 407 couples

Rapidly evolving genomic technologies have made genetic expanded carrier screening (ECS) possible for couples considering a pregnancy. The aim of ECS is to identify couples at risk of having a child affected with a severe disorder and to facilitate their reproductive decision-making process. The ECS test we offer at our center, called BeGECS (Belgian Genetic ECS), consists of 1268 autosomal recessive (AR) and X-linked pathogenic genes, including severe childhood-onset disorders. However, thus far data are scarce regarding the actual uptake of preconception ECS in a clinical setting. Therefore, our aim was to describe the characteristics of 407 couples to whom ECS was offered at the Center for Medical Genetics of the University Hospital Ghent (CMGG). In addition, we aimed to identify their reasons for accepting or declining BeGECS. Between October 2019 and January 2023, 407 preconception couples were offered BeGECS and were asked to fill in a questionnaire after their decision. Of the 407 couples participating in the survey, 270 (66%) decided to take the test and 137 (34%) declined. We observed that age, highest education level as well as indication for consultation were statistically different between the group that accepted to take the test and the group that declined (p = 0.037). In particular, age and education level were substantially higher in the group that accepted the test. Major reasons for taking BeGECS include prevention, wishing to obtain all information possible, helping preparing their future reproductive decision and increasing their sense of control by being informed. However, couples that do not chose to take BeGECS stated that too much information would make them anxious, that the result would not change their decision to have children, that they do not want to spend money on something that will not happen and that they do not worry about their family history. These findings show that the majority of preconception couples that were offered ECS, accepted the test.

Carrier frequency of autosomal recessive genetic conditions in diverse populations: lessons learned from the Genome Aggregation Database

An equitable approach by the American College of Medical Genetics and Genomics (ACMG) has recently recommended carrier screening for genes associated with moderate to severe autosomal recessive conditions with a carrier frequency of ≥1/200 in the Genome Aggregation Database exomes (gnomADv2.0.2). We analyzed carrier frequencies in gnomADv3.1.1 genomes representing diverse populations. ClinVar data on 35,996 pathogenic/likely pathogenic variants in 419 genes were used to estimate the gnomAD frequency of heterozygous carriers. We found that ninety-two genes had a carrier frequency of ≥1/200, of which 63 were shared between v3.1.1 and v2.0.2 and 29 were new in v3.1.1. Addition of new populations (Amish, Finnish and Middle Eastern) increased the number of new genes with a carrier frequency of ≥1/200 to 71. Changes in carrier frequencies were attributed to new gnomAD populations, different sample sizes, new ClinVar data, and technical differences between exomes and genomes. This study highlights the dynamic changes in carrier frequencies due to new datasets from diverse populations and provides updated carrier frequencies based on the combined data from 184,352 genomes and exomes in gnomAD. We recommend a periodic review for inclusion of new population data to update carrier screening panels in the future. This article is protected by copyright. All rights reserved.

Pathogenic variants carrier screening in New Brunswick: Acadians reveal high carrier frequency for multiple genetic disorders

BACKGROUND

Founder populations that have recently undergone important genetic bottlenecks such as French-Canadians and Ashkenazi Jews can harbor some pathogenic variants at a higher carrier rate than the general population, putting them at a higher risk for certain genetic diseases. In these populations, there can be considerable benefit to performing ethnic-based or expanded preconception carrier screening, which can help in the prevention or early diagnosis and management of some genetic diseases. Acadians are descendants of French immigrants who settled in the Atlantic Coast of Canada in the seventeenth century. Yet, the Acadian population has never been investigated for the prevalence/frequency of disease-causing genetic variants.

METHODS

An exome sequencing panel for 312 autosomal recessive and 30 X-linked diseases was designed and specimens from 60 healthy participants were sequenced to assess carrier frequency for the targeted diseases.

RESULTS

In this study, we show that a sample population of Acadians in South-East New Brunswick harbor variants for 28 autosomal recessive and 1 X-linked diseases, some of which are significantly more frequent in comparison to reference populations.

CONCLUSION

Results from this pilot study suggests a need for further investigation of genomic variation in this population and possibly implementation of targeted carrier and neonatal screening programs.

The diagnostic utility of exome-based carrier screening in families with a positive family history

Identification of disease-causing variants in families with a history of a suspected recessive disorder is essential for appropriate counseling and reproductive decision making. The present case series depicts the utility of whole exome-based phenotypes-driven carrier analysis in 14 families with a positive family history. A phenotype-based analysis revealed a putative diagnostic yield of 71.4%. Proband sample, though insufficient, was available in only one family, which allowed the diagnosis to be confirmed. In the remaining nine families, despite the detection of heterozygous pathogenic/likely pathogenic variants, only a putative diagnosis was possible due to incomplete proband phenotyping as well as nonavailability of proband samples. We describe the youngest known patient homozygous for a likely pathogenic variant in PPP1R21. He is currently asymptomatic at 7 days of life and has a simplified gyral pattern on neuroimaging. The case series, though small, captures the challenges in the diagnosis of genetic disorders in low to middle income countries with in-equitable health care access. It reinforces the significance of detailed phenotyping in the proband as well as the importance of DNA storage for a conclusive diagnosis. A recurring post-test counseling challenge was risk ascertainment and reproductive decision making in subsequent pregnancies if the detected pathogenic/likely pathogenic variants are co-inherited, in families with a putative diagnosis. When opted for, prenatal testing in such a scenario would be limited in its ability to comment on the fetal status with respect to the disorder in the proband.

Evaluating the model of offering expanded genetic carrier screening to high school students within the Sydney Jewish community

Programs offering reproductive genetic carrier screening (RGCS) to high school students within the Ashkenazi Jewish community in several countries including Canada and Australia have demonstrated high uptake and retention of educational messages over time. This study was undertaken to evaluate whether testing for an expanded number of conditions in a high school setting would impact the effectiveness of education. In this questionnaire-based study, genetic carrier testing for nine conditions was offered to 322 year 11 students from five high schools, with students attending a compulsory 1-h education session prior to voluntary testing. Comparison of pre- and post-education measures demonstrated a significant increase in knowledge, positive attitudes, and reduced concern immediately after the education session. Retention of knowledge, measures of positive attitude, and low concern over a 12-month period were significantly higher than baseline, although there was some reduction over time. In total, 77% of students exhibited informed choice regarding their intention to test. A significant increase in baseline knowledge scores and positive attitude was also demonstrated between our original 1995 evaluation (with testing for only one condition) and 2014 (testing for nine conditions) suggesting community awareness and attitudes to RGCS have increased. These findings validate the implementation of effective education programs as a key component of RGCS and are relevant as gene panels expand with the introduction of genomic technologies.

Carrier screening in the Mexican Jewish community using a pan-ethnic expanded carrier screening NGS panel

PURPOSE

The Mexican Jewish community (MJC) is a previously uncharacterized, genetically isolated group composed of Ashkenazi and Sephardi-Mizrahi Jews who migrated in the early 1900s. We aimed to determine the heterozygote frequency of disease-causing variants in 302 genes in this population.

METHODS

We conducted a cross-sectional study of the MJC involving individuals representing Ashkenazi Jews, Sephardi-Mizrahi Jews, or mixed-ancestry Jews. We offered saliva-based preconception pan-ethnic expanded carrier screening, which examined 302 genes. We analyzed heterozygote frequencies of pathogenic/likely pathogenic variants and compared them with those in the Genome Aggregation Database (gnomAD).

RESULTS

We recruited 208 participants. The carrier screening results showed that 72.1% were heterozygous for at least 1 severe disease-causing variant in 1 of the genes analyzed. The most common genes with severe disease-causing variants were CFTR (16.8% of participants), MEFV (11.5%), WNT10A (6.7%), and GBA (6.7%). The allele frequencies were compared with those in the gnomAD; 85% of variant frequencies were statistically different from those found in gnomAD (P <.05). Finally, 6% of couples were at risk of having a child with a severe disorder.

CONCLUSION

The heterozygote frequency of at least 1 severe disease-causing variant in the MJC was 72.1%. The use of carrier screening in the MJC and other understudied populations could help parents make more informed decisions.

Which types of conditions should be included in reproductive genetic carrier screening? Views of parents of children with a genetic condition

Reproductive genetic carrier screening identifies couples with an increased chance of having children with autosomal and X-linked recessive conditions. Initially only offered for single conditions to people with a high priori risk, carrier screening is becoming increasingly offered to individuals/couples in the general population for a wider range of genetic conditions. Despite advances in genomic testing technology and greater availability of carrier screening panels, there is no consensus around which types of conditions to include in carrier screening panels. This study sought to identify which types of conditions parents of children with a genetic condition believe should be included in carrier screening. Participants (n = 150) were recruited through Royal Children's Hospital (RCH) Melbourne outpatient clinics, the Genetic Support Network of Victoria (GSNV) and a databank of children with hearing loss (VicCHILD). This study found that the majority of participants support offering carrier screening for: neuromuscular conditions (n = 128/134, 95.5%), early fatal neurodegenerative conditions (n = 130/141, 92.2%), chronic multi-system disorders (n = 124/135, 91.9%), conditions which cause intellectual disability (n = 128/139, 92.1%) and treatable metabolic conditions (n = 120/138, 87.0%). Views towards the inclusion of non-syndromic hearing loss (n = 88/135, 65.2%) and preventable adult-onset conditions (n = 75/135, 55.6%) were more mixed. Most participants indicated that they would use reproductive options to avoid having a child with the more clinically severe conditions, but most would not do so for clinically milder conditions. A recurring association was observed between participants' views towards carrier screening and their lived experience of having a child with a genetic condition.

Equitable Expanded Carrier Screening Needs Indigenous Clinical and Population Genomic Data

Expanded carrier screening (ECS) for recessive monogenic diseases requires prior knowledge of genomic variation, including DNA variants that cause disease. The composition of pathogenic variants differs greatly among human populations, but historically, research about monogenic diseases has focused mainly on people with European ancestry. By comparison, less is known about pathogenic DNA variants in people from other parts of the world. Consequently, inclusion of currently underrepresented Indigenous and other minority population groups in genomic research is essential to enable equitable outcomes in ECS and other areas of genomic medicine. Here, we discuss this issue in relation to the implementation of ECS in Australia, which is currently being evaluated as part of the national Government's Genomics Health Futures Mission. We argue that significant effort is required to build an evidence base and genomic reference data so that ECS can bring significant clinical benefit for many Aboriginal and/or Torres Strait Islander Australians. These efforts are essential steps to achieving the Australian Government's objectives and its commitment "to leveraging the benefits of genomics in the health system for all Australians." They require culturally safe, community-led research and community involvement embedded within national health and medical genomics programs to ensure that new knowledge is integrated into medicine and health services in ways that address the specific and articulated cultural and health needs of Indigenous people. Until this occurs, people who do not have European ancestry are at risk of being, in relative terms, further disadvantaged.

Expanded carrier screening for preconception reproductive risk assessment: Prevalence of carrier status in a Mexican population

OBJECTIVE

Genetic carrier screening has the potential to identify couples at risk of having a child affected with an autosomal recessive or X-linked disorder. However, the current prevalence of carrier status for these conditions in developing countries is not well defined. This study assesses the prevalence of carrier status of selected genetic conditions utilizing an expanded, pan-ethnic genetic carrier screening panel (ECS) in a large population of Mexican patients.

METHODS

Retrospective chart review of all patients tested with a single ECS panel at an international infertility center from 2012 to 2018 were included, and the prevalence of positive carrier status in a Mexican population was evaluated.

RESULTS

Eight hundred five individuals were analyzed with ECS testing for 283 genetic conditions. Three hundred fifty-two carriers (43.7%) were identified with 503 pathogenic variants in 145 different genes. Seventeen of the 391 participating couples (4.34%) were identified as being at-risk couples. The most prevalent alleles found were associated with alpha thalassemia, cystic fibrosis, GJB2 nonsyndromic hearing loss, biotinidase deficiency, and familial Mediterranean fever.

CONCLUSION

Based on the prevalence and severity of Mendelian disorders, we recommend that couples who wish to conceive regardless of their ethnicity background explore carrier screening and genetic counseling prior to reproductive medical treatment.

Could maternal ethnicity be a determinant of healthcare costs for birth assistance? Insights from a retrospective hospital-based study for the implementation of a woman-centered approach in obstetrics

Background: Current policy and service provision recommend a woman-centered approach to maternity care and the development of personalized models for clinical assistance. Ethnicity has been recognized as a determinant in the risk calculation of selected obstetric complications. Based on these assumptions, our aims were to describe the linkage between baseline characteristics and maternal ethnicity and to analyze the cost for the local healthcare system, distinguishing mode of delivery, absence or presence of complications at birth, and maternal stay duration for all ethnic groups.Methods: In a 5-year period (2012-16), all women admitted for delivery at the Department of Obstetrics and Gynecology, Fondazione Policlinico Universitario "A Gemelli" IRCCS, Rome, Italy, were included in the analysis. Maternal demographics, adverse outcomes, and costs were evaluated. Economic calculations were performed by using the "diagnosis-related group" (DRG) approach.Results: A total of 18,093 patients were included in the analysis. An overall care expense of €42,663,481 was calculated. Caucasian was the main ethnicity (90.7%), with 9.3% minority groups. Vaginal delivery (VD) was the most common mode of delivery in all ethnic groups, with a global rate of 59.6%. The highest cesarean section (CS) rates were observed among Maghreb (51.5%) and Afro-Caribbean (47.8%) women. Minority groups had a doubled rate of complicated VD, primarily Afro-Caribbean women (69.9%), followed by Asian (64.1%), Maghreb (63.2%), and Latin American (62.7%) women. Afro-Caribbean women had the highest rate of complicated CS compared to the overall study population (37.6 versus 28.5%, p < .005).Conclusions: Minority groups have increased healthcare costs for birth assistance, mainly due to the higher rates of complications. In a prospective view, two strategies could be planned: first, calculating individualized risk to mitigate the clinical care charge, based on the ad hoc combination of ethnicity, mode of delivery, and obstetric complications; and second, endorsing the current financial return-on-investment opportunity tied to mitigating ethnic disparities in birth outcomes.

Beyond the Brochure: Innovations in Clinical Counseling Practices for Prenatal Genetic Testing Options

Remarkable advancements related to preconception and prenatal genetic screening have emerged in recent years. While technology and testing options are more numerous and complex; fundamental genetic counseling issues remain the same. It is essential that with any prenatal genetic testing, women have an opportunity to make informed and autonomous decisions that are consistent with their personal needs and values. Opportunities to discuss testing options, including potential benefits and limitations, are often limited in obstetric visits due to time constraints or lack of sufficient provider education. As genetic testing is not considered a routine component of antepartum care, review of information regarding testing options is imperative so women can decide which, if any, testing to pursue. Developing new strategies to address the growing complexity of prenatal testing while ensuring provider education is accurate is crucial in imparting evidence-based care. This article will arm providers with the knowledge needed to educate women about currently available prenatal genetic screening and diagnostic tests along with guidance on the essential elements and importance of genetic counseling.

Expanded carrier screening: A current perspective

Prenatal carrier screening has expanded to include a large number of genes offered to all couples considering pregnancy or with an ongoing pregnancy. Expanded carrier screening refers to identification of carriers of single-gene disorders outside of traditional screening guidelines. Expanded carrier screening panels include numerous autosomal recessive and X-linked genetic conditions, including those with a very low carrier frequency, as well as those with mild or incompletely penetrant phenotype. Therefore, the clinical utility of these panels is still subject of debate. Priority should be given to carrier screening panels that include a comprehensive set of severe childhood-onset disorders. Psychosocial support and genetic couseling should be available prior to screening and for the return of positive results. Systems are needed to reduce the risk of misinterpreting results. Finally, attention should be paid on the impact of expanded carrier screening on health care organizations and burden of cost.