The choice not to undergo genetic testing for Huntington disease: Results from the PHAROS study

Presymptomatic Testing for Huntington's Disease in Mexico: 28 Years of Experience

INTRODUCTION

Huntington's disease (HD) is a genetic neurodegenerative disorder with dominant inheritance. Our center in Mexico City has offered presymptomatic testing (PT) since 1995.

OBJECTIVE

To describe the main clinical and demographic characteristics of at-risk HD individuals who applied to the PT program, the reasons for seeking it, and the molecular results.

METHODS

A cross-sectional study was conducted with sociodemographic and clinical data of all PT applicants from 1995-2023. Reasons for seeking PT were assessed using a modified questionnaire. In addition, anxiety, and depressive symptoms before and after PT were evaluated with Beck's instruments; cognitive impairment (CI) was assessed with the Mini-Mental State Examination (MMSE) and molecular results.

RESULTS

214 people applied for PT (2.1% of the at-risk population identified in our center); 63% were women (mean age of 37.11 years). 204 (95.3%) were accepted and 190 received results. 70% indicated that the main reason for applying for PT was to inform their offspring about the risk of inheriting HD. Significant differences were observed in the reasons for seeking PT by age group. Although some subjects received treatment, Beck's instrument scores did not indicate special attention or pharmacological treatment. The MMSE showed probable CI in 20 subjects. Of those who received results, 37% were carriers of a full penetrance allele.

CONCLUSION

Our center has the only formal PT program for HD in Mexico. The reasons for seeking PT are varied and age-related. Although PT is offered to all subjects at risk for HD, uptake remains low.

The Need to Consider Context: A Systematic Review of Factors Involved in the Consent Process for Genetic Tests from the Perspective of Patients

Background: Informed consent for genetic tests is a well-established practice. It should be based on good quality information and in keeping with the patient's values. Existing informed consent assessment tools assess knowledge and values. Nevertheless, there is no consensus on what specific elements need to be discussed or considered in the consent process for genetic tests.Methods: We performed a systematic review to identify all factors involved in the decision-making and consent process about genetic testing, from the perspective of patients. Through public databases, we identified studies reporting factors that influence the decision to accept or decline genetic testing. Studies were included if they reported the perspective of patients or at-risk individuals. All articles were thematically coded.Results: 1989 articles were reviewed: 70 met inclusion criteria and 12 additional articles were identified through the references of included studies. Coding of the 82 articles led to the identification of 45 factors involved in decision-making and consent, which were initially divided into three domains: in favor of, against or with an undetermined influence on genetic testing. Each factor was also divided into three subdomains relating to the informed choice concept: knowledge, values or other. The factors in the "other" subdomain were all related to the context of testing (e.g. timing, cost, influence of family members, etc), and were present in all three domains.Conclusions: We describe the network of factors contributing to decision-making and consent process and identify the context of genetic testing as a third component to influence this process. Future studies should consider the evaluation of contextual factors as an important and relevant component of the consent and decision-making process about genetic tests. Based on these results, we plan to develop and test a more comprehensive tool to assess informed consent for genetic testing.

Psychological and Ethical Challenges of Introducing Whole Genome Sequencing into Routine Newborn Screening: Lessons Learned from Existing Newborn Screening

As a psychologist and an ethicist, we have explored empirically newborn screening consent and communication processes. In this paper we consider the impact on families if newborn screening uses whole genome sequencing. We frame this within the World Health Organization's definition of health and contend that proposals to use whole genome sequencing in newborn screening take into account the ethical, practical and psychological impact of such screening. We argue that the important psychological processes occurring in the neonatal phase necessitate a clear justification that providing risk information at this stage provides a health benefit. We illustrate how research on current newborn screening can inform whole genome sequencing debates, whilst highlighting important gaps. Obtaining explicit, voluntary, and sufficiently informed consent for newborn screening is challenging, however we stress that such consent is ethically and legally appropriate and psychologically and practically important. We conclude by outling how this might be done.

Supporting Trial Participation in People with the Huntington's Gene: A Patient-Centered, Theory-Guided Survey of Barriers and Enablers

BACKGROUND

Under-recruitment regularly impedes clinical trials, leading to wasted resources and opportunity costs. Methods for designing trial participation strategies rarely consider behavior change theory.

OBJECTIVE

Informed by the Theoretical Domains Framework, we identified factors important to participating in Huntington's disease research and provide examples of how such a theory-informed approach can make specific suggestions about how to design targeted recruitment strategies.

METHODS

We identified a range of trial participation barriers and enablers based on interviews of key informants and implemented an online survey of members of the Huntington's disease community, asking them to rate the extent to which different factors would affect likelihood to participate in a generic Huntington's disease trial.

RESULTS

From 4,195 members, we received 323 responses and 243 completed surveys (323/4,195 or 8% participation, 243/323 or 75% completion). Respondents endorsed 9 barriers and 23 enablers relevant to trial participation. Most frequently endorsed barriers were travel to the study site (69%), worry about unknown side effects (65%), trial documents being difficult to understand (64%), and participation affecting other activities (49%). Enablers included optimism about likelihood of trial participation leading to a cure (98%), helping others (98%), contributing to science (97%), and having helpful people available to help with the participation decision (89%).

CONCLUSION

Our theory-informed survey to identify barriers to and enablers of Huntington's disease trial participation identified 32 factors, from 13 theoretical domains relevant to trial participation, and suggests effective approaches for improving trial participation and patient experience.

Huntington's disease influences employment before and during clinical manifestation: A systematic review

Huntington's disease (HD) is an inherited neurodegenerative disease. People at risk for HD can choose to get predictive testing years before the clinical onset. HD is characterized by motor, cognitive and psychiatric symptoms and has a mean age at onset between 30 and 50 years, an age at which people are usually still working. This systematic review focuses on summarizing which disease-specific characteristics influence employment and working capacity in HD. Twenty-three studies were identified and showed that while employment and working capacity in HD are negatively influenced by cognitive decline and motor impairments, apathy already plays a role in the prodromal stage. Moreover, the influence of HD transcends the clinical manifestation of the disease, as some people at risk are already experiencing the impact of HD on employment through fear of or actual genetic discrimination. Employment and working capacity are not influenced by predictive testing for HD in and of itself.

Huntington's disease: nearly four decades of human molecular genetics

Huntington's disease (HD) is a devastating neurogenetic disorder whose familial nature and progressive course were first described in the 19th century but for which no disease-modifying treatment is yet available. Through the active participation of HD families, this disorder has acted as a flagship for the application of human molecular genetic strategies to identify disease genes, understand pathogenesis and identify rational targets for development of therapies.

Patient and Relative Experiences and Decision-making About Genetic Testing and Counseling for Familial ALS and FTD: A Systematic Scoping Review

Genetic testing and counseling is an emerging part of care for patients with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) and their families. This scoping review aimed to map patients' and relatives' experiences of genetic testing and counseling for familial ALS and FTD and the factors influencing their decision to proceed with testing or counseling. Informed by the Joanna Briggs Institute methodology, 5 databases were systematically searched. Thirty studies from 39 references were included. A descriptive numerical summary analysis and narrative synthesis was conducted. Mostly positive diagnostic testing experiences were reported, but issues arose due to progressive disease and discordant results. Predictive testing impacted at-risk relatives, regardless of the result received, and psychosocial sequelae ranged from relief to guilt, worry or contemplating suicide. Four reproductive testing experiences were reported. Personal, familial and practical factors, and the lived experience of disease, informed decision-making. Greater uncertainty and complexity may be faced in familial ALS/FTD than in other late-onset neurodegenerative diseases due to clinical and genetic heterogeneity, and testing limitations. Genetic counseling models of care should consider this difference to ensure that individuals with, or at risk of, ALS/FTD are effectively managed. Implications for research and practice are discussed.

Perceptions about Research Participation among Individuals at Risk and Individuals with Premanifest Huntington's Disease: A Survey Conducted by the European Huntington Association

There has been great progress in Huntington's disease (HD) research. Yet, effective treatments to halt disease before the onset of disabling symptoms are still unavailable. Scientific breakthroughs require an active and lasting commitment from families. However, they are traditionally less involved and heard in studies. Accordingly, the European Huntington Association (EHA) surveyed individuals at risk (HDRisk) and with premanifest HD (PreHD) to determine which factors affect their willingness to participate in research. Questions assessed research experience and knowledge, information sources, reasons for involvement and noninvolvement, and factors preventing and facilitating participation. The survey included 525 individuals, of which 68.8% never participated in studies and 38.6% reported limited research knowledge. Furthermore, 52% trusted patient organizations to get research information. Reasons for involvement were altruistic and more important than reasons for noninvolvement, which were related to negative emotions. Obstacles included time/financial constraints and invasive procedures, while professional support was seen as a facilitator. PreHD individuals reported less obstacles to research participation than HDRisk individuals. Overall, a high motivation to participate in research was noted, despite limited experience and literacy. This motivation is influenced by subjective and objective factors and, importantly, by HD status. Patient organizations have a key role in fostering motivation through education and support.

Ethical questions concerning newborn genetic screening

Newborn screening is a public health strategy used to identify certain diseases in the first days of life and, therefore, facilitate early treatment before the onset of symptoms. The decision of which diseases should be included in a screening goes beyond the medical perspective, including reasons for public health and health economics. There are a number of characteristics to include a disease in the screening, such as that the disorder must be a significant health problem, the natural history of the disease must be well known, a feasible and accurate test must be available, there must be a treatment that is most effective when applied before the onset of clinical symptoms and a health system must be in place that is capable of performing the procedure and subsequent monitoring. Currently, newborn screening programs are currently based on the use of biochemical markers that detect metabolites, hormones or proteins, but recently, the availability of new technology has allowed the possibility of a genetic screening. In addition to technical problems, the possibility of neonatal screening also presents a number of ethical problems. We identified and discussed six areas of particular concern: type of illness, overdiagnosis or overtreatment, information management and informed consent, data confidentiality and protection, justice and legal regulation.

Haplotyping by CRISPR-mediated DNA circularization (CRISPR-hapC) broadens allele-specific gene editing

Allele-specific protospacer adjacent motif (asPAM)-positioning SNPs and CRISPRs are valuable resources for gene therapy of dominant disorders. However, one technical hurdle is to identify the haplotype comprising the disease-causing allele and the distal asPAM SNPs. Here, we describe a novel CRISPR-based method (CRISPR-hapC) for haplotyping. Based on the generation (with a pair of CRISPRs) of extrachromosomal circular DNA in cells, the CRISPR-hapC can map haplotypes from a few hundred bases to over 200 Mb. To streamline and demonstrate the applicability of the CRISPR-hapC and asPAM CRISPR for allele-specific gene editing, we reanalyzed the 1000 human pan-genome and generated a high frequency asPAM SNP and CRISPR database (www.crispratlas.com/knockout) for four CRISPR systems (SaCas9, SpCas9, xCas9 and Cas12a). Using the huntingtin (HTT) CAG expansion and transthyretin (TTR) exon 2 mutation as examples, we showed that the asPAM CRISPRs can specifically discriminate active and dead PAMs for all 23 loci tested. Combination of the CRISPR-hapC and asPAM CRISPRs further demonstrated the capability for achieving highly accurate and haplotype-specific deletion of the HTT CAG expansion allele and TTR exon 2 mutation in human cells. Taken together, our study provides a new approach and an important resource for genome research and allele-specific (haplotype-specific) gene therapy.