Comprehensive carrier screening and molecular diagnostic testing for recessive childhood diseases

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 estimation of pathogenic variants of autosomal recessive and X-linked recessive mendelian disorders using exome sequencing data in 1,642 Thais

BACKGROUND

People with autosomal recessive disorders often were born without awareness of the carrier status of their parents. The American College of Medical Genetics and Genomics (ACMG) recommends screening 113 genes known to cause autosomal recessive and X-linked conditions in couples seeking to learn about their risk of having children with these disorders to have an appropriate reproductive plan.

METHODS

We analyzed the exome sequencing data of 1,642 unrelated Thai individuals to identify the pathogenic variant (PV) frequencies in genes recommended by ACMG.

RESULTS

In the 113 ACMG-recommended genes, 165 PV and likely PVs in 60 genes of 559 exomes (34%, 559/1642) were identified. The carrier rate was increased to 39% when glucose-6-phosphate dehydrogenase (G6PD) was added. The carrier rate was still as high as 14.7% when thalassemia and hemoglobinopathies were excluded. In addition to thalassemia, hemoglobinopathies, and G6PD deficiency, carrier frequencies of > 1% were found for Gaucher disease, primary hyperoxaluria, Pendred syndrome, and Wilson disease. Nearly 2% of the couples were at risk of having offsprings with the tested autosomal recessive conditions.

CONCLUSIONS

Based on the study samples, the expanded carrier screening, which specifically targeted common autosomal recessive conditions in Thai individuals, will benefit clinical outcomes, regarding preconception/prenatal genetic carrier screening.

Knowledge and attitudes toward expanded carrier screening between the medical staff and general population in China

OBJECTIVE

The purpose of our study was to assess the knowledge and attitudes toward expanded carrier screening (ECS) between the medical staff and general population in China.

STUDY DESIGN

It was a survey-based cross-sectional study in Chinese. We provided an online survey for the general public nationwide. We classified the population into the medical staff and general population to evaluate the knowledge gap and provide a reference for ECS's education programs. Except for obstetrician-gynecologists and nurses in the department of Obstetrics and Gynecology, other medical staff were not included in our study. A total of 1947 questionnaires were collected from July 11, 2020 to February 10, 2021. Two hundred and eighty-four questionnaires were excluded from further analysis. The remaining 1663 cases were incorporated into the final analysis. Data were analyzed using IBM SPSS Statistics 26. Comparisons between categorical variables were tested by the use of crosstabs and χ2 test.

RESULTS

The total awareness rates of the knowledge about monogenic diseases and ECS in the respondents were low, with 35.7%, 26.1%, 3.3%, 23.3%, 24.1%, 55.2%, and 23.4% for questions Q1-Q7, respectively. Medical staff had more knowledge than general population. Knowledge about monogenic diseases and ECS was positively correlated with educational level. Most respondents showed a positive attitude toward ECS: 54.4% thought ECS was necessary, and 80.5% wanted to know more about monogenic diseases.

CONCLUSION

Although the public had little knowledge about monogenic disease and ECS, most of them showed a positive attitude. Our cross-analysis showed that medical staff had more knowledge compared to general population. Pre-test education for ECS can be carried out by medical staff who are not qualified for genetic counseling. ECS training for medical staff, especially obstetrician-gynecologist and nurse in the department of Obstetrics and Gynecology, can reduce the workload of genetic counseling.

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.

The Reproductive Journey in the Genomic Era: From Preconception to Childhood

It is estimated that around 10–15% of the population have problems achieving a pregnancy. Assisted reproduction techniques implemented and enforced by personalized genomic medicine have paved the way for millions of infertile patients to become parents. Nevertheless, having a baby is just the first challenge to overcome in the reproductive journey, the most important is to obtain a healthy baby free of any genetic condition that can be prevented. Prevention of congenital anomalies throughout the lifespan of the patient must be a global health priority. Congenital disorders can be defined as structural or functional anomalies that occur during intrauterine life and can be identified prenatally, at birth, or sometimes may only be detected later during childhood. It is considered a frequent group of disorders, affecting 3–6% of the population, and one of the leading causes of morbidity and mortality. Congenital anomalies can represent up to 30–50% of infant mortality in developed countries. Genetics plays a substantial role in the pathogenesis of congenital anomalies. This becomes especially important in some ethnic communities or populations where the incidence and levels of consanguinity are higher. The impact of genetic disorders during childhood is high, representing 20–30% of all infant deaths and 11.1% of pediatric hospital admissions. With these data, obtaining a precise genetic diagnosis is one of the main aspects of a preventive medicine approach in developed countries. The field of reproductive health has changed dramatically from traditional non-molecular visual microscope-based techniques (i.e., fluorescence in situ hybridization (FISH) or G-banding karyotype), to the latest molecular high-throughput techniques such as next-generation sequencing (NGS). Genome-wide technologies are applied along the different stages of the reproductive health lifecycle from preconception carrier screening and pre-implantation genetic testing, to prenatal and postnatal testing. The aim of this paper is to assess the new horizon opened by technologies such as next-generation sequencing (NGS), in new strategies, as a genomic precision diagnostic tool to understand the mechanisms underlying genetic conditions during the “reproductive journey”.

MutationDistiller: user-driven identification of pathogenic DNA variants

MutationDistiller is a freely available online tool for user-driven analyses of Whole Exome Sequencing data. It offers a user-friendly interface aimed at clinicians and researchers, who are not necessarily bioinformaticians. MutationDistiller combines MutationTaster's pathogenicity predictions with a phenotype-based approach. Phenotypic information is not limited to symptoms included in the Human Phenotype Ontology (HPO), but may also comprise clinical diagnoses and the suspected mode of inheritance. The search can be restricted to lists of candidate genes (e.g. virtual gene panels) and by tissue-specific gene expression. The inclusion of GeneOntology (GO) and metabolic pathways facilitates the discovery of hitherto unknown disease genes. In a novel approach, we trained MutationDistiller's HPO-based prioritization on authentic genotype-phenotype sets obtained from ClinVar and found it to match or outcompete current prioritization tools in terms of accuracy. In the output, the program provides a list of potential disease mutations ordered by the likelihood of the affected genes to cause the phenotype. MutationDistiller provides links to gene-related information from various resources. It has been extensively tested by clinicians and their suggestions have been valued in many iterative cycles of revisions. The tool, a comprehensive documentation and examples are freely available at https://www.mutationdistiller.org/.

Autonomous decisions by couples in reproductive care

Background

Preconception Expanded Carrier Screening (ECS) is a genetic test offered to a general population or to couples who have no known risk of recessive and X-linked genetic diseases and are interested in becoming parents. A test may screen for carrier status of several autosomal recessive diseases at one go. Such a program has been piloted in the Netherlands and may become a reality in more European countries in the future. The ethical rationale for such tests is that they enhance reproductive autonomy. The dominant conception of autonomy is individual-based. However, at the clinic, people deciding on preconception ECS will be counselled together and are expected to make a joint decision, as a couple. The aim of the present study was to develop an understanding of autonomous decisions made by couples in the context of reproductive technologies in general and of preconception ECS in particular. Further, to shed light on what occurs in reproductive clinics and suggest concrete implications for healthcare professionals.

Main text

Based on the shift in emphasis from individual autonomy to relational autonomy, a notion of couple autonomy was suggested and some features of this concept were outlined. First, that both partners are individually autonomous and that the decision is reached through a communicative process. In this process each partner should feel free to express his or her concerns and preferences, so no one partner dominates the discussion. Further, there should be adequate time for the couple to negotiate possible differences and conclude that the decision is right for them. The final decision should be reached through consensus of both partners without coercion, manipulation or miscommunication. Through concrete examples, the suggested notion of couple autonomy was applied to diverse clinical situations.

Conclusions

A notion of couple autonomy can be fruitful for healthcare professionals by structuring their attention to and support of a couple who is required to make an autonomous joint decision concerning preconception ECS. A normative implication for healthcare staff is to allow the necessary time for decision-making and to promote a dialogue that can increase the power of the weaker part in a relationship.

Expanded Preconception Carrier Screening in Clinical Practice: Review of Technology, Guidelines, Implementation Challenges, and Ethical Quandaries

In the last 10 years, expanded preconception carrier screening has become widely available and helps patients/couples make more informed decisions with regard to their reproductive options and facilitates more effective preconception planning, prenatal diagnosis, condition-specific counseling, and condition-specific care. This review provides an overview of expanded preconception carrier screening's high-throughput genotyping and sequencing approaches, current guidelines, implementation challenges and evolving ethical quandaries.

Clinical impact and cost-effectiveness of a 176-condition expanded carrier screen

PURPOSE

Carrier screening identifies couples at high risk for conceiving offspring affected with serious heritable conditions. Minimal guidelines recommend offering testing for cystic fibrosis and spinal muscular atrophy, but expanded carrier screening (ECS) assesses hundreds of conditions simultaneously. Although medical societies consider ECS an acceptable practice, the health economics of ECS remain incompletely characterized.

METHODS

Preconception screening was modeled using a decision tree comparing minimal screening and a 176-condition ECS panel. Carrier rates from >60,000 patients, primarily with private insurance, informed disease incidence estimates, while cost and life-years-lost data were aggregated from the literature and a cost-of-care database. Model robustness was evaluated using one-way and probabilistic sensitivity analyses.

RESULTS

For every 100,000 pregnancies, 290 are predicted to be affected by ECS-panel conditions, which, on average, increase mortality by 26 undiscounted life-years and individually incur $1,100,000 in lifetime costs. Relative to minimal screening, preconception ECS reduces the affected birth rate and is estimated to be cost-effective (i.e.,<$50,000 incremental cost per life-year), findings robust to perturbation.

CONCLUSION

Based on screened patients predominantly with private coverage, preconception ECS is predicted to reduce the burden of Mendelian disease in a cost-effective manner compared with minimal screening. The data and framework herein may facilitate similar assessments in other cohorts.

Expanded genetic carrier screening in clinical practice: a current survey of patient impressions and attitudes

PURPOSE

Expanded genetic carrier screening (ECS) is an important part of gynecological practice and preconception planning. We evaluated the awareness and attitudes among women regarding ECS and factors that may influence decision-making in a family planning context.

METHODS

A 32-question survey in an academic university practice was given to 521 women who were either currently pregnant (n = 108), undergoing gynecologic care who were considering future fertility (n = 308), and considering or receiving fertility treatment (n = 105). Data are reported descriptively.

RESULTS

Forty-seven percent (n = 246) of patients were aware of ECS. Though most reported feeling positive or neutral towards ECS, 51% (n = 263) reported no desire for testing. Fifty-eight percent (n = 303) felt it beneficial to know their carrier status, and 55% (n = 257) said it was their responsibility to undergo testing. Those considering future fertility were found to have a more positive attitude towards ECS (51.4%) than those considering or receiving fertility treatment (34%). For positive carriers of a genetic disorder, 228 (49%) of patients would proceed with having their partner screened, 58 (13%) would undergo prenatal screening only and 12 (2.6%) would continue with vitro fertilization (IVF). Related to cost for ECS, 53.5% (n = 191) would be willing to pay at least $50-100 for testing, while 29% (n = 146) would not pay anything out of pocket.

CONCLUSIONS

Despite patients' beliefs that it would be beneficial and their responsibility to undergo carrier status testing, the majority reported no desire for ECS and many were unwilling to pay out of pocket. Further education is necessary to reconcile the gap between technology and patient decision-making.

HADHA and HADHB gene associated phenotypes - Identification of rare variants in a patient cohort by Next Generation Sequencing

The heterooctameric mitochondrial trifunctional protein (MTP), composed of four α- and β-subunits harbours three enzymes that each perform a different function in mitochondrial fatty acid β-oxidation. Pathogenic variants in the MTP genes (HADHA and HADHB) cause MTP deficiency, a rare autosomal recessive metabolic disorder characterized by phenotypic heterogeneity ranging from severe, early-onset, cardiac disease to milder, later-onset, myopathy and neuropathy. Since metabolic myopathies and neuropathies are a group of rare genetic disorders and their associated muscle symptoms may be subtle, the diagnosis is often delayed. Here we evaluated data of 161 patients with myopathy and 242 patients with neuropathy via next generation sequencing (NGS) and report the diagnostic yield in three patients of this cohort by the detection of disease-causing variants in the HADHA or HADHB gene. The mitigated phenotypes of this treatable disease were missed by the newborn screening, highlighting the importance of phenotype-based NGS analysis in patients with rare and clinically very variable disorders such as MTP deficiency.

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.

Expanded carrier screening: a current survey of physician utilization and attitudes

PURPOSE

Expanded carrier screening (ECS) is an available component of preconception and prenatal care. There is complexity around offering, administering, and following-up test results. The goal of this study is to evaluate current physicians' utilization and attitudes towards ECS in current practice.

METHODS

This was a prospective qualitative survey study. A 32-question electronic survey was distributed during a 1-year period to obstetricians-gynecologists who were identified using a Qualtrics listserv database.

RESULTS

While more than 90% of physicians offered ethnic-based carrier screening (CS), ECS was offered significantly less (2010, 20.6%, and 2016, 27.1%). Physicians who were not fellowship-trained in reproductive endocrinology and infertility (REI) preferred ethnic-based carrier screening (95.9 vs 16.8%; P < 0.001). REI subspecialists were more likely to offer ECS (80%) compared to 70% of maternal fetal medicine physicians (MFM). Physicians were comfortable discussing negative results (53.6%) compared to positive results (48.4%). Most physicians (56%) believed that ECS should not be offered until the significance of each disease is understood; 52% believed that testing should be restricted to those conditions important to couples; while 26% felt that testing should be done regardless of the clinical significance.

CONCLUSIONS

Discussion and application of ECS has increased in clinical practice. However, lack of comfort with counseling and varying beliefs surrounding ECS continue to hinder its utilization. Further education and training programs, and subsequent evaluation are warranted.

Attitudes of European Geneticists Regarding Expanded Carrier Screening

OBJECTIVE

To explore attitudes of clinical and molecular geneticists about the implementation of multi-disease or expanded carrier screening (ECS) for monogenic recessive disorders.

DESIGN

Qualitative; semistructured interviews.

SETTING

In person or via Skype. Interviews were audiorecorded and transcribed verbatim.

PARTICIPANTS

European clinical and molecular geneticists with expertise in carrier screening (N = 16).

METHODS

Inductive content analysis was used to identify common content categories in the data.

RESULTS

Participants recognized important benefits of ECS, but they also identified major challenges, including limited benefit of ECS for most couples in the general population, lack of knowledge on carrier screening among nongenetic health care providers and the general public, potential negative implications of ECS for society, and limited economic resources. Participants favored an evidence-based approach to the implementation of population-wide ECS and were reluctant to actively offer ECS in the absence of demonstrable benefits. However, there was a consensus among the participants that ECS should be made available to couples who request the test. In addition, they believed ECS could be routinely offered to all people who use assisted reproduction.

CONCLUSION

Although a limited ECS offer is practical, it also raises concerns over equality in access to screening. A comprehensive risk-benefit analysis is needed to determine the desirability of systematic population-wide ECS.

Swedish parents' interest in preconception genetic carrier screening

INTRODUCTION

Genetic technologies advance rapidly. It is possible to undergo genetic carrier screening before pregnancy to examine genetic risks to future offspring. We aimed to investigate parents' interest and motives towards preconception genetic carrier screening (PCS) as well as factors associated with interest in PCS.

MATERIAL AND METHODS

Our study sample consists of 777 parent couples within the longitudinal Swedish Pregnancy Planning study. Women responded to questionnaires at three occasions: in early pregnancy, late pregnancy, and one year after childbirth. Male partners responded to one questionnaire one year after childbirth.

RESULTS

One-third of the parents were positive (30% versus 34% of women and men, respectively), less than a third were negative (26% versus 28%), and 45% versus 38% were uncertain about whether to consider PCS before a future pregnancy. No differences in PCS interest were found between women and men (P = 0.091), but a higher proportion of women were concerned about negative consequences (53% versus 46%, P < 0.003) and were 'opposed to such a way of child selection' (31.8% versus 25.2%, P = 0.002). Factors associated with PCS interest were experiences of prenatal diagnostics and positive attitudes towards finding out or choosing sex of one's child (women), and prenatal diagnostics, self-rated poor health, and pregnancy planning (men).

CONCLUSION

Both women and men had relatively high uncertainty towards PCS, but women were more concerned about negative consequences. The future extent of the clinical utility of PCS is currently unknown, but parents' interests and doubts are important aspects to consider.

Population-based preconception carrier screening: how potential users from the general population view a test for 50 serious diseases

With the increased international focus on personalized health care and preventive medicine, next-generation sequencing (NGS) has substantially expanded the options for carrier screening of serious, recessively inherited diseases. NGS screening tests not only offer reproductive options not previously available to couples, but they may also ultimately reduce the number of children born with devastating disorders. To date, preconception carrier screening (PCS) has largely targeted single diseases such as cystic fibrosis, but NGS allows the testing of many genes or diseases simultaneously. We have developed an expanded NGS PCS test for couples; simultaneously it covers 50 very serious, early-onset, autosomal recessive diseases that are untreatable. This is the first, noncommercial, population-based, expanded PCS test to be offered prospectively to couples in a health-care setting in Europe. So far, little is known about how potential users view such a PCS test. We therefore performed an online survey in 2014 among 500 people from the target population in the Netherlands. We enquired about their intention to take an expanded PCS test if one was offered, and through which provider they would like to see it offered. One-third of the respondents said they would take such a test were it to be offered. The majority (44%) preferred the test to be offered via their general practitioner (GP) and 58% would be willing to pay for the test, with a median cost of [euro ]75. Our next step is to perform an implementation study in which this PCS test will be provided via selected GPs in the Northern Netherlands.

Epilepsy is not a mandatory feature of STXBP1 associated ataxia-tremor-retardation syndrome

BACKGROUND

Mutations in the STXBP1 gene (MUNC18-1) were first described to cause Ohtahara syndrome (Early infantile epileptic encephalopathy, EIEE)(12-14) characterized by very early infantile epileptic encephalopathy with frequent tonic spasms and a suppression-burst pattern on electroencephalogram. In the following years a wider phenotype was recognized having milder forms of epilepsies. All patients showed also intellectual disability and movement disorders.

METHODS

Here, we present three female patients with an ataxia-tremor-retardation syndrome caused by a de novo STXBP1 mutation. Two of the girls were diagnosed through next-generation-sequencing as mutations in STXBP1 were not suspected. The third patient was diagnosed by targeted genetic testing due to its clinical features strikingly similar to the first two girls.

RESULTS

The characteristic feature of our three patients is the lack of epilepsy which is in contrast to the majority of the patients with STXBP1 mutation.

CONCLUSION

Hence, epilepsy is not a mandatory feature of patients with a STXBP1 mutation.

Responsible implementation of expanded carrier screening

This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines.

Swedish healthcare providers' perceptions of preconception expanded carrier screening (ECS)-a qualitative study

Reproductive autonomy, medicalization, and discrimination against disabled and parental responsibility are the main ongoing ethical debates concerning reproductive genetic screening. To examine Swedish healthcare professionals' views on preconception expanded carrier screening (ECS), a qualitative study involving academic and clinical institutions in Sweden was conducted in September 2014 to February 2015. Eleven healthcare professionals including clinicians, geneticists, a midwife, and a genetic counselor were interviewed in depth using a semi-structured interview guide. The questionnaire was constructed after reviewing the main literature and meetings with relevant healthcare providers. The interviews were recorded, transcribed verbatim, and content analyzed for categories and subcategories. Participants nurtured many ethical and non-ethical concerns regarding preconception ECS. Among the ethical concerns were the potential for discrimination, medicalization, concerns with prioritization of healthcare resources, and effects on reproductive freedom. The effects of implementation of preconception ECS, its stakeholders, regulations, and motivation are some of non-ethical concerns. These concerns, if not addressed, may affect the uptake and usage of carrier screening within Swedish healthcare system. As this is a qualitative study with a small non-random sample size, the findings cannot be generalized. The participants had little to no working experience with expanded screening panels. Moreover, the interviews were conducted in English, a second language for the participants, which might have limited the expression of their views. However, the authors claim that the findings may be pertinent to similar settings in other Scandinavian countries.

Carrier Screening is a Deficient Strategy for Determining Sperm Donor Eligibility and Reducing Risk of Disease in Recipient Children

Aims: DNA-based carrier screening is a standard component of donor eligibility protocols practiced by U.S. sperm banks. Applicants who test positive for carrying a recessive disease mutation are typically disqualified. The aim of our study was to examine the utility of a range of screening panels adopted by the industry and the effectiveness of the screening paradigm in reducing a future child's risk of inheriting disease. Methods: A cohort of 27 donor applicants, who tested negative on an initial cystic fibrosis carrier test, was further screened with three expanded commercial carrier testing panels. These results were then compared to a systematic analysis of the applicants' DNA using next-generation sequencing (NGS) data. Results: The carrier panels detected serious pediatric disease mutations in one, four, or six donor applicants. Because each panel screens distinct regions of the genome, no single donor was uniformly identified as carrier positive by all three panels. In contrast, systematic NGS analysis identified all donors as carriers of one or more mutations associated with severe monogenic pediatric disease. These included 30 variants classified as “pathogenic” based on clinical observation and 66 with a high likelihood of causing gene dysfunction. Conclusion: Despite tremendous advances in variant identification, understanding, and analysis, the vast majority of disease-causing mutation combinations remain undetected by commercial carrier screening panels, which cover a narrow, and often distinct, subset of genes and mutations. The biological reality is that all donors and recipients carry serious recessive disease mutations. This challenges the utility of any screening protocol that anchors donor eligibility to carrier status. A more effective approach to reducing recessive disease risk would consider joint comprehensive analysis of both donor and recipient disease mutations. This type of high-resolution recessive disease risk analysis is now available and affordable, but industry practice must be modified to incorporate its use.

Expanded carrier screening: A review of early implementation and literature

Carrier screening is the practice of testing individuals to identify those at increased risks of having children affected by genetic diseases. Professional guidelines on carrier screening have been available for more than 15 years, and have historically targeted specific diseases that occur at increased frequencies in defined ethnic populations. Enabled by rapidly evolving technology, expanded carrier screening aims to identify carriers for a broader array of diseases and may be applied universally (equally across all ethnic groups). This new approach deviates from the well-established criteria for screening models. In this review, we summarize the rationale for expanded carrier screening using available literature regarding clinical and technical data, as well as provider perspectives. We also discuss important avenues for further research in this burgeoning field.

Targeted carrier screening for four recessive disorders: high detection rate within a founder population

In a genetically isolated community in the Netherlands four severe recessive genetic disorders occur at relatively high frequency (pontocerebellar hypoplasia type 2 (PCH2), fetal akinesia deformation sequence (FADS), rhizomelic chondrodysplasia punctata type 1 (RCDP1), and osteogenesis imperfecta (OI) type IIB/III. Over the past decades multiple patients with these disorders have been identified. This warranted the start of a preconception outpatient clinic, in 2012, aimed at couples planning a pregnancy. The aim of our study was to evaluate the offer of targeted genetic carrier screening as a method to identify high-risk couples for having affected offspring in this high-risk subpopulation. In one year, 203 individuals (92 couples and 19 individuals) were counseled. In total, 65 of 196 (33.2%) tested individuals were carriers of at least one disease, five (7.7%) of them being carriers of two diseases. Carrier frequencies of PCH2, FADS, RCDP1, and OI were 14.3%, 11.2%, 6.1%, and 4.1% respectively. In individuals with a positive family history for one of the diseases, the carrier frequency was 57.8%; for those with a negative family history this was 25.8%. Four PCH2 carrier-couples were identified. Thus, targeted (preconception) carrier screening in this genetically isolated population in which a high prevalence of specific disorders occurs detects a high number of carriers, and is likely to be more effective compared to cascade genetic testing. Our findings and set-up can be seen as a model for carrier screening in other high-risk subpopulations and contributes to the discussion about the way carrier screening can be offered and organized in the general population.

Kinderwunsch als genetisches Risiko?

Erweiterte präkonzeptionelle Anlageträgerscreenings auf seltene, rezessive Erkrankungen haben sich in jüngster Zeit als neuartige Form genetischer Diagnostik herausgebildet. Bisher werden Tests auf mehr als 100 Anlageträgerschaften von kommerziellen Unternehmen angeboten, eine künftige Übernahme in öffentliche Gesundheitssysteme wird jedoch bereits diskutiert. Falls Mann und Frau die gleiche rezessive Anlage tragen, eröffnet die Diagnostik ihnen verschiedene Alternativen, um die Geburt eines kranken Kindes zu vermeiden. Erweiterte Trägerscreenings haben jedoch problematische gesellschaftliche Implikationen und werfen ungelöste Fragen auf, u. a. wie die getesteten Krankheiten ausgewählt werden und wie eine angemessene genetische Beratung zu gewährleisten ist. Die Vermutung, die Etablierung solcher Screenings sei unvermeidbar, könnte sich als vorschnell erweisen.

Advances in Genetic Discovery and Implications for Counseling of Patients and Families with Autism Spectrum Disorders

The prevalence of autism spectrum disorders (ASD) continues to increase. Genetic factors play an important role in the etiology of ASD, although specific genetic causes are identified in only a minority of cases. Recent advances have accelerated the discovery of genes implicated in ASD through convergent genomic analysis of genome-wide association studies, chromosomal microarray, exome sequencing, genome sequencing, and gene networks. Hundreds of candidate genes for ASD have been reported, yet only a handful have proven causative. Symptoms are complex and highly variable, and most cases are likely due to cumulative genetic factors, the interactions among them, as well as environmental factors. Here we summarize recent findings in genomic research regarding discovery of candidate genes, describe the major molecular processes in neural development that may be disrupted in ASD, and discuss the implication of research findings in clinical genetic diagnostic testing and counseling. Continued advances in genetic research will eventually translate into innovative approaches to prevention and treatment of ASD.

Adult genetic risk screening

Recent advances in genetic analysis especially DNA sequencing technology open a new strategy for adult disease prevention by genetic screening. Physicians presently treat disease pathology with less emphasis on disease risk prevention/reduction. Genetic screening has reduced the incidence of untreatable childhood genetic diseases and improved the care of newborns. The opportunity exists to expand screening programs and reduce the incidence of adult onset diseases via genetic risk identification and disease intervention. This article outlines the approach, challenges, and benefits of such screening for adult genetic disease risks.