Predictive Testing For Huntington's Disease Research Articles

Psychological reactions to predictive genetic testing for Huntington's disease: A qualitative study.

There is a lack of qualitative research investigating the experience of individuals at risk for Huntington's disease (HD) during the period prior to undergoing predictive testing, as well as their reaction to the test result. This secondary analysis study aimed to explore the experiences during the predictive testing process of individuals who had been or who were at risk for HD. For the primary study, in-depth semi-structured interviews were conducted, and data were analyzed using inductive thematic analysis. We employed the explorative qualitative design for this study, which involved 33 individuals who had been or who were at risk for HD. Results indicate that many had been anticipating the onset of the disease even before they knew their mutation status. Their choice of whether to get tested or not was influenced by personal, social, and practical factors. Whether the test result was positive or negative, coping with the test result was reported to be difficult. Participants with a mutation-negative result felt a need for more follow-up consultations than what they had received. Findings indicate that the decision to undergo predictive testing for HD was not only a personal choice, but was also influenced by both proximal and distant factors. Similar to individuals who tested positive for the mutation, individuals who tested negative for the mutation may need comprehensive follow-up to adapt to the reality of the test result.

Predictive testing for Huntington disease over 24 years: Evolution of the profile of the participants and analysis of symptoms.

BackgroundHuntington disease (HD) is a devastating neurodegenerative autosomal dominant genetic condition. Predictive testing (PT) is available through a defined protocol for at‐risk individuals. We analyzed the over‐24‐years evolution of practices regarding PT for HD in a single center.MethodsWe gathered data from the files of all individuals seeking PT for HD in Lyon, France, from 1994 to 2017.Results448 out of 567 participants had exploitable data. Age at consultation dichotomized over 24 years toward an eightfold increase in individuals aged >55 (2/94 vs. 30/183; 2% to 16%; p < .0001) and twice as many individuals aged 18–20 (3/94 vs. 12/183; 3%–7%; p < .05). Motives for testing remained stable. The rate of withdrawal doubled over 24 years (9/94 vs. 38/183; 9%–21%; p < .02). Independently of the time period, less withdrawal was observed for married, accompanied, at 50% risk, and symptomatic individuals, and in those able to explicit the motives for testing or taking the test to inform their children. We also assessed the consistency between the presence of subtle symptoms compatible with HD found before the test by the team's neurologist, and the positivity of the molecular test. The concordance was 100% (17/17) for associated motor and cognitive signs, 87% (27/31) for isolated motor signs, and 70% (7/10) for isolated cognitive signs. Furthermore, 91% (20/22) of individuals who requested testing because they thought they had symptoms, were indeed found carriers.ConclusionThis over‐24 years study underlines an increasing withdrawal from protocol and a dichotomization of participants’ age. We also show a strong concordance between symptoms perceived by the neurologist or by the patient, and the subsequent positivity of the predictive molecular test.

Risk Assessment for Huntington's Disease for (Future) Offspring Requires Offering Preconceptional CAG Analysis to Both Partners.

Amongst the main reasons people at risk for Huntington's disease (HD) have for undergoing predictive genetic testing are planning a family and prevention of passing on an expanded CAG-repeat to future offspring. After having received an unfavourable test result, a couple may consider prenatal testing in the foetus or preimplantation genetic diagnostic testing (PGD) in embryos. Testing of the foetus or embryos is possible by means of direct testing of the expanded repeat. Optimal reliability in testing the foetus or embryos requires the establishment of the origin of the repeats of both parents in the foetus. For PGD the analysis is combined with or sometimes solely based on identification of the at-risk haplotype in the embryo. This policy implies that in the context of direct testing, the healthy partner's CAG repeat lengths in the HD gene are also tested, but with the expectation that the repeat lengths of the partner are within the normal range, with the proviso that the partner's pedigree is free of clinically confirmed HD. However, recent studies have shown that the expanded repeat has been observed more often in the general population than previously estimated. Moreover, we have unexpectedly observed an expanded repeat in the non-HD partner in four cases which had far-reaching consequences. Hence, we propose that in the context of reproductive genetic counselling, prior to a planned pregnancy, and irrespective of the outcome of the predictive test in the HD-partner, the non-HD partner should also be given the option of being tested on the expanded allele. International recommendations for predictive testing for HD should be adjusted.

Reverse pre-symptomatic testing for Huntington disease: double disclosure when 25% at-risk children reveal the genetic status to their parent.

Predictive testing for Huntington disease (HD) in 25% at-risk individuals is testing with full knowledge, and sometimes assuming, that the parent does not want to know his status. The goal of this study was to understand: (1) the differences in the motivation between 25% and 50% at-risk individuals to be tested and (2) the consequences of "double disclosure", including parental reactions. Test requests from 25% at-risk individuals were rare (155/1611, 10%). We compared their motivation with those of 1456 50% at-risk individuals. The principal motivation to have the test for both groups was "to know" (48% versus 58%, p = 0.049), but the desire to have children was more frequent in the 25% at-risk group (32% versus 17%, p < 0.001). Sixty percent of the 25% at-risk group went through the testing procedure: 15% (n = 14) were variant positive for HD. Testees reported four adverse reactions of their parent (22%): one committed suicide and three became depressed. This result highlights the impact of "double disclosure", a bad result for the person themselves and the transmitting parent. It is the responsibility of the team to anticipate this outcome with the 25% at-risk individuals: children revealing the genetic status to their parent. They should help the testees and their family to find a satisfactory solution to help prevent adverse reactions. This includes ensuring that the candidate is well-infomed abour the testing options and consequences to her/himself but also to her/his parent. The at-risk parent should be offered to discuss the implications of their child's testing.

A liminal stage after predictive testing for Huntington disease

BackgroundFollowing predictive testing for Huntington disease (HD), knowledge of one's carrier status may have consequences on disease onset. Our study aimed to address two questions. First, does knowledge of being...

Enhanced Detection and Sizing of the HTT CAG Repeat Expansion in Huntington Disease Using an Improved Triplet-Primed PCR Assay

Background: Accurate determination of the CAG repeat number is crucial for diagnostic and predictive testing for Huntington disease (HD). Current PCR-based assays can accurately size up to ∼110 HTT CAG repeats. Objective: To develop an improved assay capable of detecting larger CAG repeat expansions. Methods: A triplet-primed PCR (TP-PCR) assay was optimized and validated on 14 HD reference DNAs, including a sample carrying a large expansion of ∼180 CAG repeats. Results: All 14 HD reference samples showed 100% concordance with the previously verified allele sizes. For alleles under 45 CAGs, identical repeat sizes were obtained, while alleles larger than 46 CAGs were sized to within ±1 CAG. The improved TP-PCR assay successfully detected the ∼180 CAG repeat allele in an affected sample. Conclusion: This method extends the detection limit of large expanded alleles to at least ∼175-180 CAG repeats, thus reducing the likelihood of requiring Southern blot analysis for any HD-affected sample.

Impact of Huntington Disease Gene-Positive Status on Pre-Symptomatic Young Adults and Recommendations for Genetic Counselors.

Huntington disease (HD) is an autosomal dominant, progressive neurodegenerative disorder for which there is no cure. Predictive testing for HD is available to asymptomatic at-risk individuals. Approximately half of the population undergoing predictive testing for HD consists of young adults (≤35years old). Finishing one's education, starting a career, engaging in romantic relationships and becoming a parent are key milestones of young adulthood. We conducted a qualitative study to explore how testing gene-positive for HD influences young adults' attainment of these milestones, and to identify major challenges that pre-symptomatic young adults face to aid the development of targeted genetic counseling. Results of our study demonstrate that 1) knowing one's gene-positive status results in an urgency to reach milestones and positively changes young adults' approach to life; 2) testing positive influences young adults' education and career choices, romantic relationships, and family planning; 3) young adults desire flexible and tailored genetic counseling to address needs and concerns unique to this population. Findings of this study contribute to the understanding of the impact of predictive testing for HD on young adults, and highlight issues unique to this population that call for further research, intervention and advocacy.

Genetic Counselling for Predictive Testing in Huntington's Disease in One Centre since 1993. Gender-Specific Aspects of Decision-Making

The discovery of the mutation causing Huntington's disease (HD) in 1993 allowed direct mutation analysis and predictive testing to identify currently unaffected carriers with a sensitivity and specificity of virtually 100%. The present study was designed to comprehensively profile the participants who sought predictive testing for HD between 1993 and 2009 in our Huntington centre. Using a retrospective design, we analysed the written documentation of the counselling sessions for all referrals for predictive mutation testing in this time span. Six hundred sixty-three individuals at risk for HD requested predictive testing. Roughly half (n = 333) completed the protocol and received their test result. In general our findings are in accordance with other reports: most participants share an a priori risk of 50% (91.1%); more females request testing (58.5%); and those who ask for the result are mostly in their 30 s (mean = 35.1 years). Of those at 50% or 25% prior risks, 47.4% and 22.7%, respectively, tested positive in accordance with the respective risk of inheriting HD. Generally, more participants with an affected mother than father sought genetic testing (52.5% versus 47.5%). Interestingly, this difference was especially evident in the group of females who finally withdrew from testing (59.1%, p = 0.040). Men, in particular those who decided in favour of the test, were more often accompanied by their partner in the pre-test counselling session than vice versa (67.9% versus 44.7%, p = 0.003). On the other hand, significantly more men who were being tested did not have a companion in the pre-test session as compared with men who decided against the test (40.0% versus 25.7%, p = 0.012). During the first four years of predictive testing (1993–1996) more participants completed the protocol and received their test result as in later years. Yet, in this early time span significantly fewer females finally decided in favour of the test (48.4%, p = 0.005). These findings are discussed longitudinally and in the context of the experience in other centres. We present new gender-specific aspects of decision-making for predictive HD tests.

Ethical issues in predictive testing for Huntington's disease an evidence based case discussion

Purpose – Diagnosis of Huntington's disease (HD) is with genetic tests and predictive testing for HD has been available for almost two decades. In the age of advancing genetic techniques, the question arises as to how the predictive tests can affect a person, his or her family and relatives, life choices and future. The paper aims to discuss these issues. Design/methodology/approach – A case study is presented demonstrating the complex issues surrounding genetic testing in HD. Relevant literature was then reviewed to further explore ethical issues linked to predictive testing for HD and also looked into findings on resolving this complex issue. Findings – Predictive testing in HD gives rise to ethical issues in social, legal, economical and imperatively personal aspects of an individual and society. Education and dispersion of knowledge to general society, regarding the test, its impact and also the illness would be a starting point in an attempt to resolve these issues. Need for counselling and support for patients in this context is vital and hence the imperative need to ensure provisions for standardised training and supply of professionals in this setting. Universal and enforceable framework along the lines of International Huntington Association recommendation should be adopted nationally. Originality/value – This paper presents a case study with significant value in demonstrating the challenges faced by genetic testing in HD, and provides insight in to this issue significant for all clinicians.

K09 Commercially Available HD Predictive Test on Minors in Rome, Italy

Background Based on guidelines and international documents, predictive tests of unpreventable and untreatable late onset disorders, such as Huntington Disease (HD) on minors are highly discouraged. Although very few mature adolescent cases can access a predictive test, institutional genetic service organisations usually abide by the “non-testing” of minors recommendation. Aims On behalf of AICH Rome (Associazione Italiana della Corea di Hungtinton), we conducted a study with commercial laboratories in Rome, Italy, to assess their compliance with the above recommendation on predictive test for HD in minors. Methods The study entailed contacting two hundred and fifty commercial laboratories in Rome via phone. We asked to conduct an HD predictive test on a minor. cost of the test, time frames, and modalities for sharing the results. Answers were gathered from receptionists, medical doctors, and lab technicians. Results From two hundred fifty sample set, only fifteen performed predictive HD tests. All fifteen laboratories perform HD predictive tests on minors by simply securing a signed parental consent form. The only concern expressed by few of the fifteen was the difficulty of collecting blood samples from children younger than five years old because of their small veins. None of the laboratories offered genetic counselling. Conclusions Based on the sample group, we concluded that in the city of Rome, Italy, best practice protocols for HD predictive testing of either adults or minors are not followed. Efforts to initiate a dialogue at the institutional and local level that can bring about awareness and compliance of commercial laboratories with international HD predictive test guidelines have started.

Help or hindrance: young people's experiences of predictive testing for Huntington's disease.

A growing number of young people (YP) are requesting predictive testing (PT) for Huntington's disease (HD), yet there is little research in this area. The aim of this study was to explore YP's experiences of PT for HD, the impact of their result and any gaps in information or support. In-depth interviews were conducted with YP who sought PT for HD from nationally funded Genetics Services. Participants were recruited through the Grampian Genetics Service or Scottish Huntington's Association. Twelve female participants aged 17-26 years were recruited (seven below 20 years). Pre- and post-test interviews were conducted where possible. A qualitative thematic analysis suggests three main testing experiences, regardless of test result. Testing may be: (i) a journey of empowerment, (ii) an ambivalent process or (iii) a poor experience. In pre-test counselling, gaps in emotional support were highlighted. The post-test period was particularly difficult if there were unanticipated changes in family dynamics or an individual's result contradicted what they expected 'deep down'. YP's experiences of PT for HD are generally similar to those of adults, but testing may help or interfere with key issues related to this age and stage. Implications for clinical practice are outlined.

Two Decades of Huntington Disease Testing: Patient's Demographics and Reproductive Choices

Predictive testing for Huntington disease (HD) has been available in the United States (US) since 1987, and the Indiana University Predictive Testing Program has been providing this testing since 1990. To date there has been no published description of those who present for such testing in the US. Here we describe demographics of 141 individuals and reproductive decision making of a subset of 16 of those individuals who underwent predictive HD testing between 1990 and 2010 at one site in the US. This study is a retrospective chart review of the "Personal History Questionnaire" participants completed prior to testing. As seen in other studies, most participants were female (64.5 %), in their mid-30s (mean = 34), and had at least one child prior to testing (54 %). Multiple demographic datum points are described, and the reproductive decision making of these at-risk individuals was analyzed using Fisher's Exact Tests. Of those women who had children before learning of their risk to inherit HD, those who attended church more frequently, had three or more children total, or whose mother was affected with HD were more likely to be comfortable with their choice to have children. We conclude that these demographic factors influence the reproductive decision-making of individuals at risk for HD. Psychologists, clinical geneticists, and genetic counselors may be able to use this information to help counsel at-risk patients regarding current or past reproductive decision making.

Triplet Repeat Primed PCR Simplifies Testing for Huntington Disease

Diagnostic and predictive testing for Huntington disease (HD) requires an accurate determination of the number of CAG repeats in the Huntingtin (HHT) gene. Currently, when a sample appears to be homozygous for a normal allele, additional testing is required to confirm amplification from both alleles. If the sample still appears homozygous, Southern blot analysis is performed to rule out an undetected expanded HTT allele. Southern blot analysis is expensive, time-consuming, and labor intensive and requires high concentrations of DNA. We have developed a chimeric PCR process to help streamline workflow; true homozygous alleles are easily distinguished by this simplified method, and only very large expanded alleles still require Southern blot analysis. Two hundred forty-six HD samples, previously run with a different fragment analysis method, were analyzed with our new method. All samples were correctly genotyped, resulting in 100% concordance between the methods. The chimeric PCR assay was able to identify expanded alleles up to >150 CAG repeats. This method offers a simple strategy to differentiate normal from expanded CAG alleles, thereby reducing the number of samples reflexed to Southern blot analysis. It also provides assurance that expanded alleles are not routinely missed because of allele dropout.

Developing a comprehensive, effective patient-friendly website to enhance decision making in predictive testing for Huntington disease

Predictive testing for Huntington disease is a complex decision, requiring in-depth counseling, education, and evaluation. Despite the growth in Web-based decision aids and educational resources, such tools for those considering Huntington disease testing are not available. The main objective of this project was to develop a patient-friendly, comprehensive, accessible Web-based tool to provide accurate information about testing for Huntington disease. A semistructured interview study was conducted to determine the informational, educational, and support needs of those considering Huntington disease testing. A dedicated predictive testing website was subsequently developed and pilot tested. The interview study revealed that an effective website should include interactive diagrams, video documentaries, and personal stories of others who had considered testing. The pilot test revealed that the multidimensional site was easy to navigate and understand and provided an accurate, unbiased overview of the important factors to be considered before undergoing predictive testing. This project demonstrates the use of a mixed-method approach to develop the first tailored website dedicated to predictive testing for Huntington disease. Such an approach enabled the development of a comprehensive, accurate, and effective educational tool that supports informed decision making for people considering predictive testing for Huntington disease in an accessible, nonthreatening manner.

Providing predictive testing for Huntington disease via telehealth: results of a pilot study in British Columbia, Canada

Predictive testing (PT) for Huntington disease (HD) usually requires several in-person appointments which acts as a barrier to testing for those from remote regions. This pilot study reports the use of telehealth PT to examine whether such telehealth testing improves access to HD PT while maintaining quality of care and support. Individuals underwent PT via the telehealth protocol or standard in-person protocol and were asked to complete surveys regarding their experience. Results reveal no significant differences between the in-person-tested and telehealth-tested groups with respect to quality of care, information, counselling and support. The majority of participants in both groups stated that pre-test counselling had provided them with sufficient knowledge about the advantages and disadvantages of undergoing testing, the opportunity to ask questions, and the ability to make an informed decision. The majority of participants in both groups were satisfied by the manner in which results were delivered and stated they had received sufficient information regarding the implications of these results. This study reveals that telehealth PT improves access while maintaining quality of care and support.

When access is an issue: exploring barriers to predictive testing for Huntington disease in British Columbia, Canada.

Predictive testing (PT) for Huntington disease (HD) requires several in-person appointments. This requirement may be a barrier to testing so that at risk individuals do not realize the potential benefits of PT. To understand the obstacles to PT in terms of the accessibility of services, as well as exploring mechanisms by which this issue may be addressed, we conducted an interview study of individuals at risk for HD throughout British Columbia, Canada. Results reveal that the accessibility of PT can be a barrier for two major reasons: distance and the inflexibility of the testing process. Distance is a structural barrier, and relates to the time and travel required to access PT, the financial and other opportunity costs associated with taking time away from work and family to attend appointments and the stress of navigating urban centers. The inflexibility of the testing process barrier relates to the emotional and psychological accessibility of PT. The results of the interview study reveal that there are access barriers to PT that deter individuals from receiving the support, information and counseling they require. What makes accessibility of PT services important is not just that it may result in differences in quality of life and care, but because these differences may be addressed with creative and adaptable solutions in the delivery of genetic services. The study findings underscore the need for us to rethink and personalize the way we deliver such services to improve access issues to prevent inequities in the health care system.

Adoption and the communication of genetic risk: experiences in Huntington disease

Adoption agencies can use genetic information to determine the eligibility of prospective adoptive parents and to establish a child's suitability for adoption. We describe experiences and implications of communicating genetic risk for Huntington disease (HD) in the context of adoption. A secondary analysis was employed using data collected from a cross-sectional survey (n = 233) and two qualitative studies on the psychosocial effects of predictive testing for HD. We demonstrate several ethical and practical challenges in the search for and communication of genetic information for adoptees and their birth relatives. We also found that concern for adoption discrimination was reported by 13.7% of survey respondents (n = 32). Concerns were higher among tested respondents than those who had not been tested (n = 29 vs n = 3, p = 0.010). However, more respondents were concerned about being discriminated based on their family history (FHx) vs their genetic test results (GTR) (concern based on FHx: n = 18 vs based on GTR: n = 1 vs based on both: n =10). These findings contribute to the limited empirical literature by offering evidence on the experiences and implications of communicating genetic risk information in the context of adoption with reference to HD.

Huntington's disease in Greece: the experience of 14 years

A large scale genetic and epidemiological study of Huntington's disease (HD) was carried out in Greece from January 1995 to December 2008. Diagnostic testing was carried out in 461 symptomatic individuals, while 256 were tested for presymptomatic purposes. The diagnosis of HD with a CAG expansion ≥ 36 was confirmed in 278 symptomatic individuals. The prevalence of HD in Greece was estimated at approximately 2.5 to 5.4:100,000, while the mean minimum incidence was estimated at 2.2 to 4.4 per million per year. The molecular diagnosis of HD was confirmed in the majority of patients (84.4%) sent for confirmation. The false-positive cases 15.6% were characterized by the absence of a family history of HD and the presence of an atypical clinical picture. The uptake of predictive testing for HD was 8.6%. A prenatal test was requested in six pregnancies. The findings of our study do not differ significantly from those of similar studies from other European countries despite the relative genetic isolation of Greece. Of interest is the identification of clusters of HD in Greece. The presence or absence of a family history of HD should be interpreted cautiously, during the diagnostic process.

Experience over fifteen years with a protocol for predictive testing for Huntington disease

Objective To compile a comprehensive profile of the participants who had predictive testing from Huntington disease (HD) between 1994 and 2008 in Montreal, Canada. Method This is a retrospective cohort study. The predictive testing protocol consisted of a telephone interview to give information about predictive testing and collect demographic data; a psychological assessment and counseling session; a session focused on medical and family history of HD; a session reserved for genetic counseling; a session where results were given to participants; and a follow-up telephone interview. Results A total of 181 applicants requested presymptomatic testing. 135 applicants (77 women and 58 men) completed the protocol and received test results while 40 withdrew. Of the latter, 3 manifested symptoms of the disease and were referred to a neurologist or psychiatrist, and 3 had previously been tested by linkage analysis. Participants usually mentioned more than one reason for requesting predictive testing but the most frequent was to put an end to uncertainty concerning their risk of illness. The proportion of positive and negatives test results was 40% and 54.1% respectively, significantly different from the expected 50% (p < 0.01). Prenatal testing was not frequently requested. Conclusion All the participants expressed satisfaction regarding their decision to be tested. None to our knowledge had a catastrophic reaction (major depressive disorder or psychiatric hospitalization, declared suicide attempt or suicide). Our study highlights that preparation for receiving test results is a psychologically complex process for which appropriate support in a timely fashion is critical. We feel that a cautious and ethical case by case approach remains essential and that high standards of testing should be maintained because of the far reaching impact of test results.

Uptake of Huntington disease predictive testing in a complete population

Using the Northern Ireland Huntington disease (HD) register, the number of prospectively recorded predictive tests was analysed over a 20-year period. Two hundred and twelve patients completed predictive testing. Ninety-two (43%) received mutation-positive results and 119 (56%) mutation negative. There was one intermediate allele result. There was no significant gender difference. One hundred and eighty affected cases confirmed by molecular genetic testing were alive on 1 January 2001. The uptake of predictive testing in the entire HD 50% at-risk population in 2001 was calculated by three methods giving a range of 12.3-14.6%. Uptake after 20 years was estimated to be 14.7%. The minimum prevalence of affected HD cases was calculated as 10.6/100,000 in 2001. The total uptake of predictive testing was calculated and it suggests that a substantial number of at-risk patients do not come forward for testing until symptomatic. Pre-symptomatic testing for this late-onset condition with no present treatment, and limited management options, still presents challenges for families.