Testing For Huntington's Disease Research Articles

Long-term outcome of presymptomatic testing in Huntington disease

Our study on long-term outcome of presymptomatic testing for Huntington disease had two aims: the comparison of the psychological well-being and social adjustment of carriers and non-carriers of the mutation, and the identification of psychological determinants to improve care/support of testees. We performed a cross-sectional study of 351 persons who underwent presymptomatic testing. Those who had motor signs were excluded from the comparison of asymptomatic carrier and non-carriers. A structured interview including five self-report scales and the MINI (Mini International Neuropsychiatric Inventory) was proposed to detect a psychopathology or problem with social adjustment.We interviewed 119 testees (53%), 62 non-carriers and 57 carriers after a mean delay of 3.7 years (range: 0.32 to 8.9) after their result. Depression was frequent in asymptomatic carriers (58%). Interestingly, the self reported impact of the test showed that 27% of non-carriers did not cope well with a favourable result, and a significant percentage of non-carriers (24%) were depressed during follow-up. Multivariate analysis showed that only a previous episode of depression was predictive of depression after genetic testing in both carriers and non-carriers of the HD mutation (P<0.0001).Psychological support is necessary for all testees regardless of the result of their presymptomatic test, because psychiatric care is often needed by both carriers and non-carriers.

Problems assessing uptake of Huntington disease predictive testing and a proposed solution

The uptake of predictive testing for Huntington disease informs our understanding of decision making by those at risk and assists with planning for service provision. Uptake figures have been reported from several centers based on the total number of people who have undertaken predictive testing as a percentage of those estimated to be at 50% risk in the region. This method produced a figure of 35% from our own service, much higher than observation of the local pedigrees indicated, and higher than other published reports. We have identified some errors in the commonly used formula. The major errors are the use of the cumulative total of those who have had testing with a static denominator of those at 50% risk, and the failure to exclude from the at-risk group those who are too young and therefore ineligible to test.We report data from the Huntington Disease Register of Victoria and estimate the prevalence to be 8 per 100,000 in 1999. Additional data on individuals at risk were collated. We found that for every diagnosed person there were 4.2 individuals at 50% risk, a lower ratio than one to five hypothesized in the literature. We examined these ratios in the context of uptake.Significantly, we provide a solution to the calculation of uptake with a formula that factors in a dynamic denominator and corrects for the number of years testing has been offered. Using this formula, we calculated an uptake of 13.0-15.4% for the state of Victoria, Australia. This formula can be used to compare uptake across different centers.

Fear of health insurance loss among individuals at risk for Huntington disease

Genetic testing in Huntington disease, an inherited ultimately fatal neurodegenerative disorder, is infrequent despite wide availability. Factors influencing the decision to pursue testing are largely unknown. We conducted a prospective longitudinal observational study of 1,001 individuals in North America who were at risk for Huntington disease who had not pursued genetic testing prior to enrollment. We evaluated the rationale for remaining untested at baseline, determined the concerns of those who eventually pursued testing, and assessed the population's psychological attributes. We contrasted responses between those who did and did not pursue testing, and between United States and Canadian residents. The principal reasons for remaining untested were comfort with risk and uncertainty and the inability to "undo" knowledge gained. After enrollment, 83 individuals [8.3%] pursued genetic testing. Their greatest concern was losing health insurance, and 41.6% of them [vs. 6.7% of those who did not pursue testing; P < 0.001] reported paying out of pocket for testing or other medical services to conceal their genetic risk from their insurer/employer. Among individuals who were tested, more United States residents [46.1%] than Canadian residents [0.0%; P = 0.02] paid out of pocket for health services or genetic testing. Psychological attributes were similar among individuals who did and did not pursue testing. Individuals at risk for Huntington disease who pursued genetic testing feared losing medical insurance, and many paid out of pocket for medical services. Alleviating the fear of health insurance loss may help those who want to pursue genetic testing for many other conditions. [ClinicalTrials.gov number, NCT0052143].

Mental health and quality of life after genetic testing for Huntington disease: A long‐term effect study in Germany

Predictive genetic testing for Huntington disease (HD) might cause severe short-term psychological reactions in patients with poor mental health. Very few studies exist on the long-term effects of genetic HD testing. The aim of this study was to assess mental health and quality of life in persons who were tested for HD mutation, to compare mental health depending on the result of the genetic test (non-carriers, gene carriers, and patients with HD) and to identify predictors of mental health and quality of life via linear regression. The data were collected by self-report questionnaires. In total, 121 individuals participated in this study: 52 were non-carriers, 54 were gene carriers, and 15 were gene carriers suffering from HD. Non-carriers and gene carriers showed better mental health and quality of life than HD-patients but did not differ from each other. In non-carriers four variables predicted increased depression and low mental quality of life: low perceived social support, no intimate relationship, female sex and younger age. For gene carriers three predictors were found: low perceived social support, the expectation of an unfavorable genetic test result before the testing procedure and being childless. To prevent detrimental effects of HD testing on mental health and mental quality of life, specific attention should be paid to persons with limited social networks during genetic counseling. Assessment of expectations related to the test result and mental health prior to a genetic testing procedure may help to identify gene carriers at risk of poor coping after an unfavorable test result.

“You're one of us now”: Young people describe their experiences of predictive genetic testing for Huntington disease (HD) and familial adenomatous polyposis (FAP)

There has been much debate about the psychosocial effects of predictive genetic testing in minors. The majority of this debate has been theoretical, with little empirical evidence published. We conducted in-depth interviews with 18 young people who had undergone testing, to explore the range of harms and benefits that they perceived were associated with their tests. Participants were eight individuals who were tested for Huntington disease (two gene-positive, six gene-negative) and ten who were tested for familial adenomatous polyposis (five gene-positive, five gene-negative). At the time of their test they ranged from 10 to 25 years of age. When interviewed they ranged from 14 to 26 years of age. Harms described included knowledge of future illness, witnessing distress in parents, negative effects on family relationships and friendships, effects upon employment and school, experiencing regret, feeling guilty and having to confront difficult issues. Benefits included knowledge of gene-negative status, relief from uncertainty, witnessing relief in parents, feeling able to plan for the future, positive effects on family relationships and friendships, feeling empowered and experiencing a sense of clarity about what is important in life. Harms were described in relation to gene-negative test results, as were benefits in relation to gene-positive test results. The testing process itself had several positive and negative effects for young people, distinct from the actual test result. Future research concerning the effects of predictive genetic testing in young people must remain broad and should aim to measure the beneficial as well as the harmful effects that resonate for young people themselves.

Engagement with genetic discrimination: concerns and experiences in the context of Huntington disease

It has been over 20 years since the inception of predictive testing for Huntington disease (HD), yet the social implications of knowing one's genetic risk for HD have not been fully explored. Genetic discrimination (GD) is a potential risk associated with predictive testing. Although anecdotal reports of GD have been documented, there is a paucity of research on the nature and experiences of GD in the context of HD. The purpose of this study was to describe the concerns and experiences of GD in the HD community. Semistructured interviews were conducted with 45 genetically tested and 10 untested individuals and analyzed using grounded theory methods. Our findings demonstrate that a majority of individuals were concerned about (37/55) and experienced GD (32/55) across a variety of contexts that extend beyond the traditionally examined contexts of insurance and employment to include family, social, government, and health-care domains. We describe a process of engagement with GD in which individuals formed meaningful interpretations of GD and personalized its risk and consequences in their lives. Our findings provide an insight into some of the specific processes and factors influencing engagement with GD. These results help identify areas where more education and support is needed and provide direction to genetic professionals supporting their clients as they confront issues of GD and genetic testing.

Defining purpose: a key step in genetic test evaluation

The introduction of new genetic tests, like other medical innovations, can be conceptualized as a three-step process. Tests are proposed for use based on research findings and clinical reasoning; an evaluation occurs; and judgments are made about clinical use and reimbursement (Fig. 1). The evaluation may be informal, as when a clinician determines whether a new test will be helpful in a particular patient encounter, or formal, as when a practice guideline panel utilizes a defined methodology to assess a test or a health care funder utilizes a set of criteria to determine test coverage. Although genetic tests are often described in terms of technology, a full evaluation requires that the test be considered as a clinical process in which the laboratory assay, or other testing procedure, is done to acquire information about a particular health condition, in a defined population, for a specific clinical purpose.1 Genetic tests have a wide range of health care applications. They are used to confirm the presence of a genetic condition, identify reproductive risks, and select preventive therapy. Testing occurs in newborn screening programs and in primary, specialty, and prenatal care, and may be initiated on the basis of clinical symptoms, family history, or population demographics. Genetic tests also utilize a range of technologies, and vary considerably in their predictive value. This diversity poses a challenge for the evaluation process. Several groups have considered methods for genetic test evaluation,2–5 and model programs for systematic evaluation have been established in the United States (Evaluation of Genomic Applications in Practice and Prevention6) and the UK (the UK Genetic Testing Network7). To date, however, the evaluation process has not fully addressed the clinical diversity of genetic tests. The Evaluation of Genomic Applications in Practice and Prevention project has focused on genetic tests related to common disorders and drug therapy, whereas the United Kingdom Genetic Testing Network has primarily addressed tests for single gene disorders. An effort by the Secretary’s Advisory Committee on Genetic Testing to categorize genetic tests into those requiring higher versus lower levels of scrutiny was not successful.8 To address the challenge of genetic test diversity, we propose an outcome-orientated taxonomy for defining test purpose. A focus on health outcomes allows the definition of a small and informative set of purposes for genetic testing, despite the range of technologies and clinical settings in which testing occurs. Defining test purpose in turn clarifies the benefits to be expected from the testing process, and provides guidance to clinicians and policy makers concerning the evidence needed to support test use. Defining test purpose, therefore, is an important first step in genetic test evaluation.

Development of genomic reference materials for Huntington disease genetic testing

PurposeDiagnostic and predictive testing for Huntington disease requires an accurate measurement of CAG repeats in the HD (IT15) gene. However, precise repeat sizing can be technically challenging, and is complicated by the lack of quality control and reference materials (RM). The aim of this study was to characterize genomic DNA from 14 Huntington cell lines available from the National Institute of General Medical Sciences Human Genetic Cell Repository at the Coriell Cell Repositories for use as reference materials for CAG repeat sizing. MethodsFourteen Huntington cell lines were selected for study. The alleles in these materials represent a large range of sizes that include important diagnostic cutoffs and allele combinations. The allele measurement study was conducted by ten volunteer laboratories using a variety of polymerase chain reaction-based in-house developed methods and by DNA sequence analysis. ResultsThe Huntington alleles in the 14 genomic DNA samples range in size from 15 to 100 CAG repeats. There was good agreement among the ten laboratories, and thus, the 95% confidence interval was small for each measurement. The allele size determined by DNA sequence analysis agreed with the laboratory developed tests. ConclusionThese DNA materials, which are available from Coriell Cell Repositories, will facilitate accurate and reliable Huntington genetic testing.

Maladie de Huntington : l'expérience du test présymptomatique, du diagnostic prénatal et préimplantatoire

Presymptomatic testing for Huntington disease has been available for 15 years. The possibility of determining the genetic status of an at-risk person for the disorder which runs in his or her family raises questions because of the absence of preventive treatments. In addition, being carrier does not allow to determine when the disease starts and how it will evolve, impairing the possibilities of planning the future. A pluridisciplinary approach to predictive testing with care before, during and after the test taking into account the medical, social and psychological aspects of the disease is good practice. At the present time, only a minority of at-risk individuals request presymptomatic testing and almost 50% do not pursue until the results. The consequences of the test may be harmful, more frequently after an unfavorable than after a favorable result. Motivations and the outcome in terms of request for prenatal testing after a carrier result are known today and the number or prenatal testing remains very limited. Preimplantation genetic testing is an alternative for couples who knows or do not their own genetic status. We report our experience in two French centres: Paris for presymptomatic and prenatal testing and Strasbourg for preimplantation diagnosis.

“Holding your breath”: Interviews with young people who have undergone predictive genetic testing for Huntington disease

Guidelines recommend that predictive genetic testing for Huntington disease (HD) should be deferred until the age of majority (18 years in most countries). However, opposition to these guidelines exists, with some professionals arguing that testing may be beneficial for young people, and should be considered much earlier. Empirical evidence is unable to substantiate either position. We aimed to (1) explore the experience of predictive genetic testing for HD from the young person's perspective and to (2) document the impact that testing has upon various aspects of young people's lives. Eight young people who had undergone predictive genetic testing for HD were interviewed. They ranged in age from 17 to 25 years at the time of their test. Four were female and two had received a gene-positive test result. Interviews were taped, transcribed and analyzed thematically. Three themes emerged related to the time before the test was performed: "Living as though gene-positive," "Risk behaviors," and "Complex pasts." Two themes emerged related to the time after testing: "Identity difficulties" and "Living again." When the young people spoke about their experiences of predictive testing, they placed these within a broader context of growing up in a family affected by HD. For some of the young people, uncertainty about their genetic status constituted a barrier in their lives and prevented them from moving forward. Testing alleviated these barriers in some cases and helped them to move forward and make significant behavioral changes. Not one of the young people interviewed regretted undergoing predictive testing.

The roles of family members, health care workers, and others in decision-making processes about genetic testing among individuals at risk for Huntington disease

PurposeTo understand how individuals at risk for Huntington disease view the roles of others, e.g., family members and health care workers, in decision making about genetic testing. MethodsTwenty-one individuals (eight mutation-positive, four mutation-negative, and nine not tested) were interviewed for approximately 2 hours each. ResultsInterviewees illuminated several key aspects of the roles of family members and health care workers (in genetics and other fields) in decision making about testing that have been underexplored. Family members often felt strongly about whether an individual should get tested. Health care workers provided information and assistance with decision making and mental health referrals that were often helpful. Yet health care workers varied in knowledge and sensitivity regarding testing issues, and the quality of counseling and testing experiences can range widely. At times, health care workers without specialized knowledge of Huntington disease offered opinions of whether to test. Input from families and health care workers could also conflict with each other and with an individual's own preferences. Larger institutional and geographic contexts shaped decisions as well. ConclusionDecision-making theories applied to Huntington disease testing have frequently drawn on psychological models, yet the current data highlight the importance of social contexts and relationships in testing decisions. This report, the first to our knowledge to explore individuals' perceptions of social factors (particularly family and health care worker involvement) in Huntington disease testing decisions, has critical implications for practice, education, research, and policy.

Managing genetic discrimination: Strategies used by individuals found to have the Huntington disease mutation

The introduction of predictive testing for Huntington disease (HD) over 20 years ago has led to the advent of a new group of individuals found to have the HD mutation that are currently asymptomatic, yet destined in all likelihood to become affected at some point in the future. Genetic discrimination, a social risk associated with predictive testing, is the differential treatment of individuals based on genotypic difference rather than physical characteristics. While evidence for genetic discrimination exists, little is known about how individuals found to have the HD mutation cope with the potential for or experiences of genetic discrimination. The purpose of this study was to explore how individuals found to have the HD mutation manage the risk and experience of genetic discrimination. Semi-structured individual interviews were conducted with 37 individuals who were found to have the HD mutation and analysed using grounded theory methods. The findings suggest four main strategies: "keeping low", minimizing, pre-empting and confronting genetic discrimination. Strategies varied depending on individuals' level of engagement with genetic discrimination and the nature of the experience (actual experience of genetic discrimination or concern for its potential). This exploratory framework may explain the variation in approaches and reactions to genetic discrimination among individuals living with an increased risk for HD and may offer insight for persons at risk for other late-onset genetic diseases to cope with genetic discrimination.

Fifteen years of experience in predictive testing for Huntington disease at a single testing center in Victoria, Australia

Purpose: This retrospective study describes 15 years of experience in predictive testing for Huntington disease at a single center in Victoria, Australia.Method: Data collected on 756 participants included age, gender, family history, prior risk and the age at which this risk became known, exposure to Huntington disease, number of children, and proximity to the testing center.Results: Some 57.8% of participants were female, and 88.8% had a 50% risk of developing Huntington disease. The mean age at entry was 40.4 years and was gender-independent. Of all completed tests (n = 648), 37.5% gave high-risk results, and 3.2% were in the zone of reduced penetrance. The 14.3% who withdrew from testing tended to be younger and childless, lacked exposure to severe Huntington disease, and more often at 25% or less risk. Some 32.4% of candidates presented for testing within 1 year of becoming aware of their risk, and most of these individuals had little or no exposure to severe Huntington disease. Those whose exposure was considerable waited on average for more than 13 years. Among the most inexperienced candidates were a group of “adoptees” (raised away from their biological family). Maternal transmission was the source of risk for 19 of 20 adoptees.Conclusion: This study illustrates the significance of exposure to Huntington disease and its impact on the timing of testing.

Predictive and pre‐natal testing for Huntington Disease in Australia: results and challenges encountered during a 10‐year period (1994–2003)

This study summarizes 10-years' experience of predictive and pre-natal testing and pre-implantation genetic diagnosis (PGD) for Huntington disease (HD) in Australia. Results are presented from 2036 direct mutation predictive tests conducted between January 1994 and December 2003. Thirty-eight per cent of results (776/2036) were positive, 56% (1140/2036) were negative, and 6% (120/2036)) were in the mutable normal (27-35 CAG repeats) or in the reduced penetrance (36-39 CAG repeats) ranges. Ninety-four per cent (1908/2036) and 6% (128/2036) of those tested had prior genetic risks of 50% and 25%, respectively. Twenty-seven per cent (34/128) of those at 25% risk had their genetic status changed to positive, thus revealing the positive status of their at-risk parent. During this period, 63 pre-natal tests were also conducted, and 13 children were born following PGD for HD. Social workers specializing in predictive testing counselling over this 10-year period across Australia identified and summarized particularly challenging counselling issues. These included the interpretation of mutable normal and reduced penetrance range test results, potential conflicts of interest between family members regarding testing decisions, unanticipated consequences of both predictive and pre-natal testing decisions, the importance of following protocols for predictive testing to facilitate long-term adjustment to results, and the potential for genetic discrimination. The identified issues highlight the importance of the protocols for predictive testing and indicate that extension of the international guidelines published in 1994 may be timely.

Predictive testing for Huntington disease: interpretation and significance of intermediate alleles

Direct mutation analysis for Huntington disease (HD) became possible in 1993 with the identification of an expanded CAG trinucleotide repeat as the mutation underlying the disease. Expansion of CAG length beyond 35 repeats may be associated with the clinical presentation of HD. HD has never been seen in a person with a CAG size of <36 repeats. Intermediate alleles are defined as being below the affected CAG range but have the potential to expand to >35 CAG repeats within one generation. Thus, children of intermediate allele carriers have a low risk of developing HD. Currently, the intermediate allele range for HD is between 27 and 35 CAG repeats. In this study, we review the current knowledge on intermediate alleles for HD including the CAG repeat range, the intermediate allele frequency, and the clinical implications of an intermediate allele predictive test result. The factors influencing CAG repeat expansion, including the CAG size of the intermediate allele, the sex and age of the transmitting parent, the family history, and the HD gene sequence and haplotype, will also be reviewed.

Perspectives towards predictive testing in Huntington disease

Genetic counseling for individuals undergoing presymptomatic testing is lacking in India although testing is easily available. This has an impact on family members of Huntington's disease (HD), an autosomal dominant disease, wherein the age at onset of symptoms varies. We examine if attitudes differ towards presymptomatic testing for HD amongst HD family members, physicians and laypersons. A modified questionnaire enquiring about opinions on various personal, family, social and future health care with regards to presymptomatic testing of HD was designed. A physician explained briefly about HD and presymptomatic testing of HD and recorded responses of unaffected family members of HD (n=25) and laypersons (n=50). Medical doctors (n=50) answered the questionnaire based on their knowledge of HD. HD family members, Medical doctors and laypersons were similar in their opinion to undergo the testing. Majority (60%) of HD family members did not wish to communicate test results with their friends when compared to the other two groups. Medical doctors and HD family members were more concerned about certainty of developing disease when the test results are positive. Majority (80%) of Medical doctors and less than half in the other groups felt that their decision to have a child would strongly depend on test results. Large proportion (80%) of HD family members did not wish to report their test results to their employers. Individuals with knowledge about HD and the test differ in their decision of sharing test results and reproductive choices.

Adverse effects of predictive testing for Huntington disease underestimated: long-term effects 7-10 years after the test.

The 7-10-year psychological effects of presymptomatic testing for Huntington disease are described in 142 individuals and 104 partners. Questionnaires included the Beck Hopelessness Scale (A. T. Beck, A. Weissman, D. Lester, & L. Trexler, 1974), the Impact of Event Scale (M. J. Horowitz, N. Wilner. & W. Alvarez. 1979). and the General Health Questionnaire (D. P. Goldberg. 1972). Carriers and their partners were more distressed immediately after the test result, although their outlooks improved somewhat in the 2-3-year posttest period. However, they became more pessimistic thereafter, when approaching the age of onset. Carriers, who were lost to follow-up after disclosure of test results, reported more distress pretest than did retained carriers. This demonstrates that studies that report few harmful effects may have underestimated the real impact. Moreover, follow-up studies need to investigate time effects for longer than a few years.

Technical Standards and Guidelines for Huntington Disease Testing

One mission of the ACMG Laboratory Quality Assurance (QA) Committee is to develop standards and guidelines for clinical genetics laboratories, including cytogenetics, biochemical, and molecular genetics specialties. This document was developed under the auspices of the Molecular Subcommittee of the Laboratory QA Committee by the Huntington Disease (HD) Working Group. These guidelines are not to be interpreted as restrictive or the only approach but to provide a helpful guide. Certainly, appropriately trained and credentialed laboratory directors have flexibility to utilize various testing platforms and design testing strategies with considerable latitude. We felt that it was essential to include technique-specific guidelines of several current technologies commonly used in laboratories providing HD testing, because the technologies discussed are available commercially and are widely utilized. We take the view that these technologies may change, and thus this document may change with future review.

DNA Testing for Huntington Disease in the Turkish Population

Huntington disease (HD) is an autosomal dominant inherited disease, characterized by involuntary movements, behavioral and personality changes and dementia. Although the mean age at onset is about 40 years, onset varies from 5 to 79 years. Therefore, at-risk individuals are never sure to have escaped the disease. The genetic defect is a CAG trinucleotide repeat expansion at the 5′ end of the IT-15 gene on chromosome 4. In this study, we analyzed 127 patients with HD and 122 healthy controls. The numbers of CAG repeats varied from 38 to 78 (median: 42) in 127 HD patients, while in healthy controls we observed only 10–35 CAG repeats (median: 18). The length of the CAG repeat expansion in Turkish HD patients and normal controls was similar to that reported from other populations. Negative correlations (r = –0.67) were also found between age of disease onset and repeat length.

Ambiguous loss and disenfranchised grief: the impact of DNA predictive testing on the family as a system.

DNA predictive testing to diagnose the presence of hereditary disease in asymptomatic individuals has become increasingly available. Information provided by these tests has implications for all relatives. In an exploratory study we examined the impact, from the family's perspective, of predictive DNA testing for Huntington disease on the family as a system. Central to their stories was a sense of loss and grief that was perhaps unique to the testing situation. The description of these losses is presented in the context of ambiguous loss as defined by Boss, disenfranchised grief as presented by Doka, and anticipatory grief as addressed by Rolland. These theories suggest clinical interventions that can be used by healthcare professionals to help families adjust to the psychosocial consequences of testing.