Predictive testing for Huntington's disease: I. Predictors of uptake in South Wales

In Wales, predictive testing for Huntington's disease (HD) has not been offered proactively to families and uptake of testing is low in comparison to other centres. Little is known of those not requesting testing, particularly those not in direct contact with the genetics service. This study examined differences between a cohort of 22 test applicants and a random group of 32 'non-requesters', drawn from the South Wales HD register. Respondents were interviewed by means of a semi-structured schedule in their own homes. The study groups differed significantly on a number of variables including: knowledge of the availability of testing; perceived attitudes of family members and significant others to testing; length of knowledge and perceived stressfulness of being at risk; and perceived ability to cope with an unfavourable result. Overall, knowledge of testing procedures was poor and at-risk individuals' understanding of genetic terminology was at odds with scientific distinctions. Discussion focuses on the organisational and psychological factors associated with lack of knowledge of the availability of testing and the interpretation of reported coping capacities.     

Reproductive decision making before and after predictive testing for Huntington's disease: an Australian perspective

A retrospective study examined both pre- and post-result reproductive decision making for 281 people at risk for Huntington's disease aged 18-45 years who had undergone predictive testing in one centre in Australia between 1990 and 2002. Forty-eight per cent of subjects had one or more pre-result pregnancies, and of these, three had prenatal linkage testing. One high-risk (50%) pregnancy was terminated. Four couples chose an alternative reproductive option. Following testing, data were available for 231 subjects, and no significant difference was found between mutation carriers and non-carriers in the occurrence of post-result pregnancies. This contrasts with the finding of a recent European study, although the outcome of the present study may have been influenced by loss of follow-up data for 50 subjects. Five carriers (17%) had a total of six prenatal tests. Four showed a carrier result and these pregnancies were terminated. Two carriers utilized an alternative reproductive option (donor insemination and pre-implantation genetic diagnosis). The results of this study confirm previous findings of a low uptake of prenatal testing and alternative reproductive options by people at risk for Huntington's disease undergoing predictive testing.     

Predictive testing for Huntington's disease: relationship with partners after testing

This study focuses on the partner relationship of tested persons, 5 years after their predictive test result for Huntington's disease (HD). We describe changes in marital status, quality of the relationship, and perceived changes in the relationship. Twenty-six carriers, 14 of their partners, 33 non-carriers, and 17 of their partners participated in the study. Qualitative and quantitative methods were used. For the majority of tested persons (about 70%), the marital status was unchanged 5 years post test. Overall, carriers rated the quality of the relationship higher than their partners did and they perceived more positive changes. Qualitative data show that a test result leading to changed roles may induce significant marital distress. Another consequence of the test may be the changes in dynamics in asymptomatic carrier couples. A pre-test discussion of the possible impact of the test result on the relationship should result in a better preparation for and more understanding of the reactions after testing. Counselling after testing should stimulate an open communication between partners with consideration of needs and anxieties of both partners.     

Predictive,pre-natal and diagnostic genetic testing for Huntington's disease: the experience in Canada from 1987 to 2000

Predictive and pre-natal testing for Huntington's Disease (HD) has been available since 1987. Initially this was offered by linkage analysis, which was surpassed by the advent of the direct mutation test for HD in 1993. Direct mutation analysis provided an accurate test that not only enhanced predictive and pre-natal testing, but also permitted the diagnostic testing of symptomatic individuals. The objective of this study was to investigate the uptake, utilization, and outcome of predictive, pre-natal and diagnostic testing in Canada from 1987 to April 1, 2000. A retrospective design was used; all Canadian medical genetics centres and their affiliated laboratories offering genetic testing for HD were invited to participate. A total of 15 of 22 centres (68.2%), currently offering or ever having offered genetic testing for HD, responded, providing data on test results, demographics, and clinical history. A total of 1061 predictive tests, 15 pre-natal tests, and 626 diagnostic tests were performed. The uptake for predictive testing was approximately 18% of the estimated at-risk Canadian population, ranging from 12.5% in the Maritimes to 20.7% in British Columbia. There appears to have been a decline in the rate of testing in recent years. Of the predictive tests, 45.0% of individuals were found to have an increased risk, and a preponderance of females (60.2%) sought testing. A greater proportion of those at < or = 25% risk sought predictive testing once direct CAG mutation analysis had become available (10.9% after mutation analysis vs 4.7% before mutation analysis, p = 0.0077). Very few pre-natal tests were requested. Of the 15 pre-natal tests, 12 had an increased risk, resulting in termination of pregnancy in all but one. Diagnostic testing identified 68.5% of individuals to be positive by mutation analysis, while 31.5% of those with HD-like symptoms were not found to have the HD mutation. The positive diagnostic tests included 24.5% of individuals with no known prior family history of HD.     

Psychological consequences and predictors of adverse events in the first 5 years after predictive testing for Huntington's disease

The promise of genetic medicine is to provide information, based on genotype, to persons not yet sick about their risk of future illness. However, little is known of the long-term psychological effects for asymptomatic persons learning their risk of having a serious disease. Predictive genetic testing for Huntington's disease (HD) has been offered for the longest time for any disease. In the present study, the psychological consequences of predictive testing were assessed prospectively in individuals at risk for HD during seven visits over 5 years. Questionnaires of standard measures of psychological distress (the General Severity Index of the Symptom Check List-90-Revised), depression (the Beck Depression Inventory), and general well-being (the General Well-Being Scale) were administered to the participants. A significant reduction in psychological distress was observed for both result groups throughout 2 years (p < 0.001) and at 5 years (p = 0.002). Despite the overall improvement of the psychological well-being, 6.9% (14 of 202) of the participants experienced an adverse event during the first 2 years after predictive testing that was clinically significant. The frequency of all defined adverse events in the participants was 21.8%, with higher frequency in the increased risk group (p = 0.03) and most occurring within 12 months of receiving results.     

Self-selection in predictive testing for Huntington's disease

Several studies have reported favorable psychological reactions to predictive testing for Huntington's disease (HD). However, few atrisk persons have been tested, and there is evidence that some at-risk people avoid testing because they fear being unable to cope with the information. Favorable psychological reactions may result from self-selection of persons who believe they are better-equipped to handle “bad news.” We surveyed 32 at-risk persons who had considered, but not chosen, testing and 66 persons who had been previously tested. Twelve persons decided not to be tested (No group); 20 persons postponed testing until some later date (Maybe group). Of the two untested groups, a significantly greater number of the No group had not been tested because they anticipated problems associated with their emotional reactions. The persons in the Tested group had less often anticipated problems with their emotional reactions; and among the minority who had anticipated some problems, most did not question their ability to cope. We conclude that the Tested persons are psychologically selected for favorable responses to genetic testing. Surveys of health professionals suggest that a sizable minority would disclose genetic disease risk whether or not people want it. Thus, people who would not choose to be tested might be persuaded to do so, or have results thrust upon them. We should be wary about assuming that the generally favorable reactions to HD testing will continue when testing becomes more widespread, as is likely to happen with simplification of the technology and acceptance of these tests by the medical community. © 1994 Wiley-Liss, Inc.     

Predictive testing for Huntington disease in a developing country

Predictive testing for Huntington disease (HD), by means of direct mutation analysis, has been offered at the Division of Human Genetics, University of Cape Town, from 1995. The aim of this study was to compile a comprehensive profile of the participants who had undergone predictive testing in the Western Cape from 1995 to 2005. The sociodemographic data, uptake and outcome of tests were analyzed to inform changes to improve the current genetic counseling services. A retrospective cross-sectional design using a 'multi-method' approach of both qualitative and quantitative methods was used. Data were gathered from the participants' hospital files and genetic database. Psychosocial data were obtained by face-to-face interviews with the participants in their homes or venues of choice. A total of 36 predictive tests were performed. The uptake for predictive testing was approximately 4.5% of the estimated at-risk population. The cohort of 27 individuals comprised 16 females and 11 males. Their mean age was 35.3 years; 6 were mixed ancestry and 21 were White people (European ancestry); 11 tested gene positive, 15 gene negative and 1 was in the reduced penetrance range. The most important issue identified was that the uptake of individuals classified as mixed ancestry was substantially lower than that of the White people possibly due to limited access to the predictive testing program because of the low levels of income and education in the general population of families with HD. Strategies to address these aspects have been incorporated into the program and will be reassessed after 1 year.     

Decreasing uptake of predictive testing for Huntington's disease in a German centre: 12 years' experience (1993-2004)

In this retrospective study, we examined changes in decision-making for and against the predictive genetic test for Huntington's disease including 478 persons at risk who had undergone genetic counselling in one centre in Germany between 1993 and 2004. At the outset of the counselling procedure the majority of subjects (71%) wanted to make use of the test, yet the actual demand of the predictive test result declined from 67 to 38% over the years. In addition, the time interval between counselling session and blood withdrawal was reduced, as determined by the counselees: in 2000-2004 the majority of persons at risk made the appointment for blood withdrawal after the shortest possible time span. Demographic factors of the cohort remained comparatively stable in the investigated time period. An association was evident between the ratio of test usage and the counselling person. These and other possible factors influencing the time flow of predictive DNA testing are discussed. Further studies are necessary to investigate whether changes of test demand rates are a general phenomenon.     

Psychological costs and benefits of predictive testing for Huntington's disease

The impact of predictive genetic testing for Huntington's disease (HD) was assessed in 68 persons at high (n = 17) or low risk (n = 51) for the disease at one to six years following disclosure of test results. There was consensus in both groups that knowledge of HD genetic status was beneficial. A majority of persons felt relief from wondering and uncertainty. High-risk persons identified greater family closeness and financial security. For low-risk persons, the knowledge that their children were spared offered great consolation. Negative effects in high-risk persons were psychological burden (worry, guilt). Even for low-risk subjects, there was a period of adjustment and, in some, disappointment that low risk had not alleviated problems unrelated to HD. Although the majority of marriages were unaffected by testing, some persons in both groups reported that their marriages sustained positive or negative impact. Despite mixed consequences, most did not regret being tested. The benefits of testing appear to outweigh its drawbacks, at least among this self-selected group of research participants. We also must conclude, however, that predictive genetic testing will result in negative as well as positive consequences, regardless of test outcome. © 1994 Wiley-Liss, Inc.     

Reactions to predictive testing in Huntington disease: Case reports of coping with a new genetic status

A predictive testing program for Huntington disease has been available in Stockholm, Sweden since October 1990. Psychosocial assessments were performed throughout the testing program to evaluate the impact of the risk situation itself and the effect of predictive testing, and to identify those individuals who were most vulnerable to severe stress and anxiety reactions. All subjects underwent neurological, neuropsychological, and psychiatric examinations. Individuals undergoing predictive testing were assessed twice by a genetic counsellor before receiving their results, and at 10 days (gene carriers only) and then 2, 6, 12, and 24 months after receiving the results. The process of coping with the test results and the psychological adjustment to knowledge about new genetic status have been shown to vary considerably. In this report, we describe the results obtained from two gene carriers and two noncarriers. The four persons chosen represent different ways of coping with the outcome of the test and of integrating knowledge about their genetic status into everyday life. These cases illustrate common themes and recurrent problems often surfacing during the counselling and testing process. The longitudinal evaluations provide information about the impact, adaptation, and long-term effects of living with a new genetic status. Am. J. Med. Genet. 73:356–365, 1997. © 1997 Wiley-Liss, Inc.     

To test or not to test: an ethical conflict with presymptomatic testing of individuals at 25% risk for Huntington's disorder

The first presymptomatic test for Huntington's disease was developed in the 1980s. With the detection of the gene causing the disorder in 1993, it became possible to do direct mutation tests with almost 100% sensitivity and specificity. The author discusses some of the ethical issues that arise when an adult child at 25% risk for the disease wishes to have the test, but the parent(s) at 50% risk refuses to have one. If the child tests positive, the genetic status of the parent will also be disclosed. No matter what course of action is chosen in this situation, the ethically legitimate interests of either child or parent might be violated. The author examines different alternatives and suggests a solution that might be acceptable to all parties.     

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.     

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.     

Predictive testing for Huntington disease: social characteristics and knowledge of applicants, attitudes to the test procedure and decisions made after testing

An investigation has been made of the social characteristics and knowledge and experience of Huntington disease (HD) for the first 80 individuals considering presymptomatic testing (applicants) at the medical genetics centres in Edinburgh and Glasgow and of attitudes to the test procedure and decisions made after testing for those who received a result. Sixty-one percent of applicants were female and 31% were over 40 years old. Almost all had a symptomatic parent but 38% did not know HD was in their family until they were over 25 years old and 48% had never received genetic counselling. Thirty-eight percent of applicants first heard of the test at the genetic clinic, 20% from a relative and 20% from the media, but none had received information from their GP. Thirty-one applicants did not have the test because they voluntarily withdrew (17 individuals), their family structure was unsuitable or no informative result was possible (11 individuals), or they were diagnosed clinically as being affected (3 individuals). Those who voluntarily withdrew did not differ significantly from the 49 who received a result in social characteristics or knowledge and experience of HD. Twenty-two individuals were found to be at increased risk (IR) (>50% of becoming affected) and 27 to be at decreased risk (DR) (< 50% of becoming affected). There was a median period of 9 months between entering the test procedure and receiving a result and the main criticism of the procedure was that it took too long to complete and several individuals experienced considerable anxiety while awaiting their result. One year after receiving their result, almost 40% of individuals had made major life decisions, mainly in the areas of personal relationships, career and financial matters and over a third of fecund individuals in both IR and DR groups had changed their decision about future childbearing. Eighty-five percent of the IR group and 53% of the DR group requested continued follow up after the 1-year follow-up visit. The majority wanted follow up by the genetic clinician, but we have found that in practice many individuals do not attend when offered clinic appointments after this time.     

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.     

The motivation of at-risk individuals and their partners in deciding for or against predictive testing for Huntington''s disease

Sixty-six percent of the at-risk persons and 74% of the partners in a large survey in Belgium have the intention of making use of predictive testing for Huntington's disease. One third of them, however, have expressed the intention of postponing the final decision for various reasons. The intention to be tested is not at all related to sociodemographic characteristics. A thorough exploration of the reasons for being in favour of or against taking the test reveals that the motivation inspiring this very personal decision is very complex. In the group of at-risk persons, less than half of the variation in the intention to be tested is explained by the role of a series of specific reasons as predictor variables in a regression analysis. The proportion of explained variation is slightly higher in the group of partners. 'To have certainty about my own future' and 'to make arrangements for the future' play a major part in the decision of the total group. 'Making decisions concerning children' and to a larger extent 'informing children about their risk status' are important factors in deciding in favour of the test.     

Predictive testing for Huntington disease in Canada: Adverse effects and unexpected results in those receiving a decreased risk

By January 1, 1991 a total of 388 persons had enrolled in the Canadian collaborative study of predictive testing for Huntington disease (HD). Of these participants, 105 persons have been given a decreased risk result. Contrary to expectations, approximately 10% of persons with a decreased risk result have had psychological difficulties coping with their new status. Here, we describe the individual responses of 6 such persons and experiential themes emerging after following these persons for up to 2 years. Individuals who are more likely to suffer an adverse reaction to a decreased risk result include those persons who have made irreversible decisions based on the belief they would develop HD or those who had unrealistic overoptimistic expectations of the positive effects of a decreased risk result. In contrast to those receiving an increased risk result, the most vulnerable time for persons receiving a decreased risk result is between 2 and 12 months after learning the outcome. The need for assessment and counselling of participants in predictive testing programs, even when there is a decreased risk result, is emphasized.