Genetic Carrier Screening in the Twenty-first Century

Reproductive genetic carrier screening in pregnancy: improving health outcomes and expanding access

Reproductive genetic carrier screening (RGCS) serves to screen couples for their risk of having children affected by monogenic conditions. The included conditions are mostly autosomal recessive or X-linked with infantile or early-childhood onset. Cystic fibrosis, spinal muscular atrophy, and hemoglobinopathies are now recommended by the American College of Obstetricians and Gynecologists (ACOG) for universal screening. Recommendations for further RGCS remain ethnicity based. The American College of Medical Genetics and Genomics and the National Society of Genetic Counselors in recent years have recommended universal expanded-panel RGCS and moving towards a more equitable approach. ACOG guidelines state that offering RGCS is an acceptable option, however it has not provided clear guidance on standard of care. Positive results on RGCS can significantly impact reproductive plans for couples, including pursuing in vitro fertilization with preimplantation genetic testing, prenatal genetic testing, specific fetal or neonatal treatment, or adoption. RGCS is a superior approach compared to ethnicity-based carrier screening and moves away from single race-based medical practice. We urge the obstetrics and gynecology societies to adopt the guidelines for RGCS put forward by multiple societies and help reduce systemic inequalities in medicine in our new genetic age. Having national societies such as ACOG and the Society for Maternal-Fetal Medicine officially recommend and endorse RGCS would bolster insurance coverage and financial support by employers for RGCS. The future of comprehensive reproductive care in the age of genomic medicine entails expanding access so patients and families can make the reproductive options that best fit their needs.

Expanded carrier screening for reproductive risk assessment: An evidence-based practice guideline from the National Society of Genetic Counselors

Expanded carrier screening (ECS) intends to broadly screen healthy individuals to determine their reproductive chance for autosomal recessive (AR) and X-linked (XL) conditions with infantile or early-childhood onset, which may impact reproductive management (Committee Opinion 690, Obstetrics and Gynecology, 2017, 129, e35). Compared to ethnicity-based screening, which requires accurate knowledge of ancestry for optimal test selection and appropriate risk assessment, ECS panels consist of tens to hundreds of AR and XL conditions that may be individually rare in various ancestries but offer a comprehensive approach to inherited disease screening. As such, the term "equitable carrier screening" may be preferable. This practice guideline provides evidence-based recommendations for ECS using the GRADE Evidence to Decision framework (Guyatt et al., BMJ, 2008, 336, 995; Guyatt et al., BMJ, 2008, 336, 924). We used evidence from a recent systematic evidence review (Ramdaney et al., Genetics in Medicine, 2022, 20, 374) and compiled data from peer-reviewed literature, scientific meetings, and clinical experience. We defined and prioritized the outcomes of informed consent, change in reproductive plans, yield in identification of at-risk carrier pairs/pregnancies, perceived barriers to ECS, amount of provider time spent, healthcare costs, frequency of severely/profoundly affected offspring, incidental findings, uncertain findings, patient satisfaction, and provider attitudes. Despite the recognized barriers to implementation and change in management strategies, this analysis supported implementation of ECS for these outcomes. Based upon the current level of evidence, we recommend ECS be made available for all individuals considering reproduction and all pregnant reproductive pairs, as ECS presents an ethnicity-based carrier screening alternative which does not rely on race-based medicine. The final decision to pursue carrier screening should be directed by shared decision-making, which takes into account specific features of patients as well as their preferences and values. As a periconceptional reproductive risk assessment tool, ECS is superior compared to ethnicity-based carrier screening in that it both identifies more carriers of AR and XL conditions as well as eliminates a single race-based medical practice. ECS should be offered to all who are currently pregnant, considering pregnancy, or might otherwise biologically contribute to pregnancy. Barriers to the broad implementation of and access to ECS should be identified and addressed so that test performance for carrier screening will not depend on social constructs such as race.

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.

Beyond the "Jewish panel": the importance of offering expanded carrier screening to the Ashkenazi Jewish population

Objective

To assess whether or not the current American College of Obstetricians and Gynecologists (ACOG) recommendations regarding carrier screening are sufficiently robust in detecting mutations in the Ashkenazi Jewish (AJ) population.

Design

Cross-sectional study.

Setting

Outreach program at university community center.

Patient(s)

Self-identified Jewish students, 18–24 years of age, interested in genetic carrier testing.

Intervention(s)

Expanded carrier screening (ECS) with the use of a commercially available targeted genotyping panel including >700 mutations in 180 genes.

Main Outcome Measure(s)

Gene mutations found in this population were grouped into three categories based on ACOG’s 2017 committee opinion regarding carrier screening: category 1: the four commonly recommended genetic conditions known to be a risk for this population; category 2: 14 genetic disorders that should be considered for more comprehensive screening, including those of category 1; and category 3: the ECS panel, which includes category 2.

Result(s)

A total of 81 students underwent screening and 36 (44.4%) were ascertained to be carriers of at least one mutation. A total of 45 mutations were identified, as 8 students were carriers for more than one condition. If testing were limited to category 1, 84% of the mutations would not have been identified, and if limited to category 2, 55% of mutations would have gone undetected.

Conclusion(s)

Individuals of Ashkenazi Jewish descent are at significant risk for carrying a variety of single-gene mutations and therefore they should be offered panethnic ECS to increase the likelihood of detecting preventable disorders.

Choices, attitudes, and experiences of genetic screening in Latino/a and Ashkenazi Jewish individuals

Genetic screening to inform personal risk has only recently become an option as the cost of sequencing decreases, and our ability to interpret sequence variants improves. Studies have demonstrated that people want to learn about their genetic information and do well after learning it, but minorities are underrepresented in these studies. We surveyed Ashkenazi Jewish (AJ) and Latino/a participants in a genetic screening study to solicit choices about genetic results to return, as well as their experience with learning these results and attitudes about genetic information secrecy and security. Participants had the option to proceed through the study self-guided, and few elected to have traditional pre-test genetic education and counseling. Despite this, the majority were satisfied with the process of selecting and receiving genetic results and felt that they understood their results. Concerns about privacy and confidentiality of genetic data were minimal, though some participants expressed modest concerns about keeping any potential results secret or the confidentiality of their genetic information. Our results support the feasibility of the option of self-guided genetic screening. Additional care will need to be taken when designing population-based screening studies to meet the needs of participants who come from communities with different experiences with genetics.

Reflex Testing for Germline BRCA1, BRCA2, PALB2, and ATM Mutations in Pancreatic Cancer: Mutation Prevalence and Clinical Outcomes From Two Canadian Research Registries

Purpose

We investigated the translational value of reflex testing for germline mutations in four homology-directed DNA repair predisposition genes ( BRCA1, BRCA2, PALB2, and ATM) in consecutive patients with pancreatic adenocarcinoma.

Methods

One hundred fifty patients with French-Canadian (FC) ancestry were evaluated for founder mutations, and 114 patients were subsequently assessed by full gene sequencing and multiplex ligation-dependent probe amplification for nonfounder mutations. Two hundred thirty-six patients unselected for ancestry were also assessed for mutations by full gene sequencing.

Results

The FC founder mutation prevalence among the 150 patients was 5.3% (95% CI, 2.6% to 10.3%), and the nonfounder mutation prevalence across the four genes among the 114 patients tested was 2.6% (95% CI, 0.6% to 7.8%). In the case series unselected for ancestry, 10.0% (95% CI, 2.7% to 26.4%) of patients reporting Ashkenazi Jewish (AJ) ancestry carried an AJ founder mutation, with no nonfounder mutations identified. The mutation prevalence among patients without FC/AJ ancestry was 4.9% (95% CI, 2.6% to 8.8%). Mutations were more frequent in patients diagnosed at ≤ 50 years of age ( P = .03) and in patients with either two or more first- or second-degree relatives with pancreas, breast, ovarian or prostate cancer, or one such relative and a second primary of one of these cancer types ( P < .001). BRCA1, BRCA2, and PALB2 carriers with late-stage (III or IV) disease had an overall survival advantage ( P = .049), particularly if treated with platinum-based chemotherapies ( P = .030).

Conclusion

Considering these results, we recommend reflex founder mutation testing of patients with FC/AJ ancestry and full gene sequencing of patients who are ≤ 50 years or meet the identified family history criteria. Reflex testing of all incident patients for these four genes may become justified as full gene sequencing costs decline.

Recommendations regarding the genetic and immunological study of reproductive dysfunction

In this article several members of diverse scientific associations and reproduction experts from Spain have updated different genetic and immunological procedure recommendations in couples affected by reproductive dysfunction with the goal of providing a set of useful guidelines for the clinic. The laboratory test has been considered as highly recommendable for making clinical decisions when the result of the diagnostic test is relevant, moderately recommendable when the results are of limited evidence because they are inconsistent, and low when the benefit of the test is uncertain. It is expected that these recommendations will provide some useful guidelines for the diagnosis, prognosis and treatment of couples presenting reproductive dysfunction.

Assessment of willingness to pay for expanded carrier screening among women and couples undergoing preconception carrier screening

Background

Expanded carrier screening can provide risk information for numerous conditions. Understanding how individuals undergoing preconception expanded carrier screening value this information is important. The NextGen study evaluated the use of genome sequencing for expanded carrier screening and reporting secondary findings, and we measured participants’ willingness to pay for this approach to understand how it is valued by women and couples planning a pregnancy.

Methods

We assessed 277 participants’ willingness to pay for genome sequencing reporting carrier results for 728 gene/condition pairs and results for 121 secondary findings. We explored the association between attitudes and demographic factors and willingness to pay for expanded carrier screening using genome sequencing and conducted interviews with 58 of these participants to probe the reasoning behind their preferences.

Results

Most participants were willing to pay for expanded carrier screening using genome sequencing. Willingness to pay was associated with income level and religiosity, but not risk status for a condition in the carrier panel. Participants willing to pay nothing or a small amount cited issues around financial resources, whereas those willing to pay higher amounts were motivated by “peace of mind” from carrier results.

Conclusion

Women and couples planning a pregnancy value genome sequencing. The potentially high out-of-pocket cost of this service could result in healthcare disparities, since maximum amounts that participants were willing to pay were higher than a typical copay and related to income.

Outcomes of an International Workshop on Preconception Expanded Carrier Screening: Some Considerations for Governments

Background

Consideration of expanded carrier screening has become an emerging issue for governments. However, traditional criteria for decision-making regarding screening programs do not incorporate all the issues relevant to expanded carrier screening. Further, there is a lack of consistent guidance in the literature regarding the development of appropriate criteria for government assessment of expanded carrier screening. Given this, a workshop was held to identify key public policy issues related to preconception expanded carrier screening, which governments should consider when deciding whether to publicly fund such programs.

Methods

In June 2015, a satellite workshop was held at the European Society of Human Genetics Conference. It was structured around two design features: (1) the provision of information from a range of perspectives and (2) small group deliberations on the key issues that governments need to consider and the benefits, risks, and challenges of implementing publicly funded whole-population preconception carrier screening.

Results

Forty-one international experts attended the workshop. The deliberations centered primarily on the conditions to be tested and the elements of the screening program itself. Participants expected only severe conditions to be screened but were concerned about the lack of a consensus definition of “severe.” Issues raised regarding the screening program included the purpose, benefits, harms, target population, program acceptability, components of a program, and economic evaluation. Participants also made arguments for consideration of the accuracy of screening tests.

Conclusion

A wide range of issues require careful consideration by governments that want to assess expanded carrier screening. Traditional criteria for government decision-making regarding screening programs are not a “best fit” for expanded carrier screening and new models of decision-making with appropriate criteria are required. There is a need to define what a “severe” condition is, to build evidence regarding the reliability and accuracy of screening tests, to consider the equitable availability and downstream effects on and costs of follow-up interventions for those identified as carriers, and to explore the ways in which the components of a screening program would be impacted by unique features of expanded carrier screening.