Early Detection of Huntington Disease

A review of quality of life after predictive testing for and earlier identification of neurodegenerative diseases

The past decade has witnessed an explosion of evidence suggesting that many neurodegenerative diseases can be detected years, if not decades, earlier than previously thought. To date, these scientific advances have not provoked any parallel translational or clinical improvements. There is an urgency to capitalize on this momentum so earlier detection of disease can be more readily translated into improved health-related quality of life for families at risk for, or suffering with, neurodegenerative diseases. In this review, we discuss health-related quality of life (HRQOL) measurement in neurodegenerative diseases and the importance of these "patient reported outcomes" for all clinical research. Next, we address HRQOL following early identification or predictive genetic testing in some neurodegenerative diseases: Huntington disease, Alzheimer's disease, Parkinson's disease, Dementia with Lewy bodies, frontotemporal dementia, amyotrophic lateral sclerosis, prion diseases, hereditary ataxias, Dentatorubral-pallidoluysian atrophy and Wilson's disease. After a brief report of available direct-to-consumer genetic tests, we address the juxtaposition of earlier disease identification with assumed reluctance toward predictive genetic testing. Forty-one studies examining health-related outcomes following predictive genetic testing for neurodegenerative disease suggested that (a) extreme or catastrophic outcomes are rare; (b) consequences commonly include transiently increased anxiety and/or depression; (c) most participants report no regret; (d) many persons report extensive benefits to receiving genetic information; and (e) stigmatization and discrimination for genetic diseases are poorly understood and policy and laws are needed. Caution is appropriate for earlier identification of neurodegenerative diseases but findings suggest further progress is safe, feasible and likely to advance clinical care.

Cognitive decline in prodromal Huntington Disease: implications for clinical trials

BACKGROUND AND OBJECTIVE

Controversy exists regarding the feasibility of preventive clinical trials in prodromal Huntington disease (HD). A primary limitation is a lack of outcome measures for persons with the gene mutation who have not yet been diagnosed with HD. Many longitudinal studies of cognitive decline in prodromal HD have not stratified samples based on disease progression, thereby obscuring differences between symptomatic and nonsymptomatic individuals.

METHODS

Prodromal participants from PREDICT-HD were stratified by disease progression into one of three groups: those having a High, Medium, or Low probability of motor manifestation within the next 5 years. Data from a total of N=1299 participants with up to 5950 data points were subjected to linear mixed effects regression on 29 longitudinal cognitive variables, controlling for age, education, depression, and gender.

RESULTS

Performance of the three prodromal HD groups was characterised by insidious and significant cognitive decline over time. Twenty-one variables from 19 distinct cognitive tasks revealed evidence of a disease progression gradient, meaning that the rate of deterioration varied as a function of progression level, with faster deterioration associated with greater disease progression. Nineteen measures showed significant longitudinal change in the High group, nine showed significant change in the Medium group and four showed significant cognitive decline in the Low group.

CONCLUSIONS

Results indicate that clinical trials may be conducted in prodromal HD using the outcome measures and methods specified. The findings may help inform interventions in HD as well as other neurodegenerative disorders.

Strategies used by teens growing up in families with Huntington disease

The purpose of this study was to identify helpfulness of strategies used by teens growing up in families with Huntington disease (HD). Forty-four participants responded to a mailed HD Family Survey-Teens Strategies. Strategies were those with strong positive correlation between use and perceived helpfulness, and those with negative or inverse relationships. Obtaining information, thinking about or doing something else, and actions on behalf of the parent with HD were rated as highest use and perceived helpfulness. Emotional suppression had high use but low helpfulness. Participants reported using numerous helpful strategies. Social support was often unavailable to help manage teen concerns.

Development of the Huntington disease work function scale

OBJECTIVE

A work function measure specific for persons with prodromal Huntington disease (HD) was created to assist with workplace accommodations.

METHODS

A self-report HD Work Function (HDWF) measure was developed from focus group and expert validation.

RESULTS

Pilot studies with 238 people with prodromal HD, and 185 companions; and 89 people without prodromal HD, and 70 companions indicate that HDWF has acceptable internal consistency (Cronbach α = 0.77), acceptable interrater reliability (r = 0.58), and acceptable convergent validity with selected items from the Endicott Work Productivity Scale (r = -0.56), Social Adjustment Scale-Self Report (r = -0.29), and Everyday Cognition (r = -0.70). The HDWF can distinguish between people with prodromal HD and people with an HD family history who do not have prodromal HD (P < 0.0001).

CONCLUSIONS

The HDWF is a brief self-assessment that may be used to monitor work function.

Couples' coping in prodromal Huntington disease: a mixed methods study

Huntington disease (HD) includes a prodromal phase with behavioral, cognitive, and motor function decline occurring up to 15 years prior to diagnosis. This study used mixed methods to examine how people in the prodromal phase and their companions coped with noticed changes. Twenty-three couples completed a semi-structured interview and Brief COPE. Participants with prodromal HD used acceptance, emotional support, and planning most frequently; companions used acceptance, planning, and active coping. Least frequently used coping strategies for each were denial, behavioral disengagement, and substance use. Qualitative interviews revealed coping strategies not included in the Brief COPE. Participants with prodromal HD used prescription medications, coping as a couple, hope, and self-monitoring; companions used hope and helping their partners. Many of the coping procedures were rated as effective, especially when changes were not severe. Couples may benefit from counseling that emphasizes using active coping strategies for changes that can be compensated for and acceptance for changes that cannot in prodromal HD. Findings from this study may be helpful for counseling patients and significant others facing other neurodegenerative conditions with prodromal or early phases, such as Alzheimer disease and Parkinson disease.

Monitoring Huntington's disease progression through preclinical and early stages

Huntington's disease (HD) is an autosomal dominant progressive neurodegenerative disorder that typically begins in middle adulthood. The neurodegenerative process that underlies HD, however, likely begins many years before clinical diagnosis. Since genetic testing can identify individuals that will develop HD during this preclinical period, clinical trials aiming to slow disease progression will likely focus on this phase of the illness in an effort to delay disease onset. How to best measure the efficacy of potential disease-modifying therapies in preclinical HD remains a complex challenge. This article will review the clinical and imaging measures that have been assessed as potential markers of disease progression in preclinical and early symptomatic HD.

Neurodegenerative disease: Establishing a clinical trial battery for Huntington disease

The success of clinical trials in Huntington disease (HD) will depend to a large degree on the quality of the outcome measures. Using data from the TRACK-HD study, a recent publication proposes a battery of assessments that could be used as outcomes in future clinical trials in patients with early HD.

Indexing disease progression at study entry with individuals at-risk for Huntington disease

The identification of clinical and biological markers of disease in persons at risk for Huntington disease (HD) has increased in efforts to better quantify and characterize the epoch of prodrome prior to clinical diagnosis. Such efforts are critical in the design and implementation of clinical trials for HD so that interventions can occur at a time most likely to increase neuronal survival and maximize daily functioning. A prime consideration in the examination of prodromal individuals is their proximity to diagnosis. It is necessary to quantify proximity so that individual differences in key marker variables can be properly interpreted. We take a data-driven approach to develop an index that can be viewed as a proxy for time to HD diagnosis known as the CAG-Age Product Scaled or CAP(S) . CAP(S) is an observed utility variable computed for all genetically at-risk individuals based on age at study entry and CAG repeat length. Results of a longitudinal receiver operating characteristic (ROC) analysis showed that CAP(S) had a relatively strong ability to predict individuals who became diagnosed, especially in the first 2 years. Bootstrap validation provided evidence that CAP(S) computed on a new sample from the same population could have similar discriminatory power. Cutoffs for the empirical CAP(S) distribution can be used to create a classification for mutation-positive individuals (Low-Med-High), which is, useful for comparison with the naturally occurring mutation-negative Control group. The classification is an improvement over the one currently in use as it is based on observed data rather than model-based estimated values. © 2011 Wiley-Liss, Inc.

Cognitive impairment in Huntington disease: diagnosis and treatment

Cognition has been well characterized in the various stages of Huntington disease (HD) as well as in the prodrome before the motor diagnosis is given. Although the clinical diagnosis of HD relies on the manifestation of motor abnormalities, the associated impairments have been growing in prominence for several reasons. First, research to understand the most debilitating aspects of HD has suggested that cognitive and behavioral changes place the greatest burden on families, are most highly associated with functional decline, and can be predictive of institutionalization. Second, cognitive impairments are evident at least 15 years prior to the time at which motor diagnosis is given. Finally, cognitive decline is associated with biological markers such as brain atrophy, circulating levels of brain-derived neurotrophic factors, and insulin-like growth factor 1. Efforts are now underway to develop valid and reliable measures of cognition in the prodrome as well as in all stages of HD so that clinical trials can be conducted using cognitive outcomes.

Biological markers of cognition in prodromal Huntington's disease: a review

Huntington's disease (HD), an autosomal-dominant genetic disorder, has historically been viewed as a degenerative movement disorder but it also includes psychiatric symptoms and progressive cognitive decline. There has been a lack of consensus in the literature about whether or not cognitive signs can be detected in carriers before clinical (motor) onset of the disease, i.e., prodromal HD. However, recently validated mathematical formulas to estimate age of clinical onset, refined over the past 5-7 years, have allowed researchers to overcome the methodological limitation of treating all prodromal carriers as a homogenous high-risk group (i.e., whether they may be 2 or 15 years from diagnosis). Here we review 23 articles on the HD prodrome, all of which related cognition to a biological marker of disease burden (i.e., genetic load, neuroimaging). All studies found at least one cognitive domain was associated with disease burden in prodromal HD participants. There was greater variability in both the detection and cognitive domain affected in those farther from onset (or those with less pathology) while most studies reliably found declines in visuomotor performance and working memory in those closer to onset. These findings indicate that cognitive signs can be reliably detected in the HD prodrome when comparing cognition to additional disease markers, however, there continues to be significant variability on cognitive findings among large and methodologically rigorous studies. This may reflect true heterogeneity in the prodromal HD phenotype which must be further explored by analyzing intra-individual variance, determining demographic risk factors associated with decline/protection, and examining if particular HD families exhibit distinct cognitive profiles. These and additional future directions are discussed.

Perceived stress in prodromal Huntington disease

This study examines perceived stress and its relationship to depressive symptoms, life changes and functional capacity in a large sample of individuals who are positive for the Huntington disease (HD) gene expansion but not yet diagnosed. Participants were classified by estimated proximity to HD diagnosis (far, mid, near) and compared with a non-gene-expanded comparison group. Persons in the mid group had the highest stress scores. A significant interaction between age and time since HD genetic testing was also found. Secondary analyses using data from a different data collection point and including a diagnosed group showed the highest stress scores in the diagnosed group. Possible explanations and implications are discussed.

An item response analysis of the motor and behavioral subscales of the unified Huntington's disease rating scale in huntington disease gene expansion carriers

Although the Unified Huntington's Disease Rating Scale (UHDRS) is widely used in the assessment of Huntington disease (HD), the ability of individual items to discriminate individual differences in motor or behavioral manifestations has not been extensively studied in HD gene expansion carriers without a motor-defined clinical diagnosis (ie, prodromal-HD or prHD). To elucidate the relationship between scores on individual motor and behavioral UHDRS items and total score for each subscale, a nonparametric item response analysis was performed on retrospective data from 2 multicenter longitudinal studies. Motor and behavioral assessments were supplied for 737 prHD individuals with data from 2114 visits (PREDICT-HD) and 686 HD individuals with data from 1482 visits (REGISTRY). Option characteristic curves were generated for UHDRS subscale items in relation to their subscale score. In prHD, overall severity of motor signs was low, and participants had scores of 2 or above on very few items. In HD, motor items that assessed ocular pursuit, saccade initiation, finger tapping, tandem walking, and to a lesser extent, saccade velocity, dysarthria, tongue protrusion, pronation/supination, Luria, bradykinesia, choreas, gait, and balance on the retropulsion test were found to discriminate individual differences across a broad range of motor severity. In prHD, depressed mood, anxiety, and irritable behavior demonstrated good discriminative properties. In HD, depressed mood demonstrated a good relationship with the overall behavioral score. These data suggest that at least some UHDRS items appear to have utility across a broad range of severity, although many items demonstrate problematic features.

Personal factors associated with reported benefits of Huntington disease family history or genetic testing

AIMS

A family history of Huntington disease (HD) or receiving results of HD predictive genetic testing can influence individual well-being, family relationships, and social interactions in positive and negative ways. The aim of this study was to examine benefits reported by people with an HD family history or those who have undergone predictive HD testing, as well as the personal variables associated with perceived benefits.

METHODS

Seventy-four of 433 people completing the International Response of a Sample Population to HD risk (I-RESPOND-HD) survey reported benefits. Knowledge and understanding was perceived as the most common benefit from participants in both groups. The next most frequent perceived benefits from a family history were connecting with others and achieving life meaning and insights. The next most common perceived benefits from genetic testing were life planning and social support. The least common perceived benefit for both groups was renewed hope and optimism. Older age and spirituality were significantly associated with benefits in both groups.

CONCLUSIONS

Perceptions of benefit may not be as likely until later years in people with prodromal HD. A developed sense of spirituality is identified as a personal resource associated with the perception of benefit from genetic testing for HD. Associations among spirituality, perceived benefits, and other indicators of personal and family well-being may be useful in genetic counseling and health care of people with prodromal HD.

Couples' attributions for work function changes in prodromal Huntington disease

People who have tested positive for the expanded Huntington disease (HD) gene who are not yet diagnosed (pre-HD) and their companions report subtle changes in ability of people with pre-HD to do their jobs. However, it is not known whether they attribute these changes to HD. Semi-structured telephone interviews were analyzed from seven persons with pre-HD at different estimated points from diagnosis and six companions. Data were analyzed using qualitative analysis methods. Participants made attributions related to health, work, and temperament. Only one participant attributed a change to HD. The process of forming attributions was demonstrated through symptom monitoring and comparison of participants with pre-HD to others with and without HD. Participants also expressed uncertainty regarding how to make attributions. Attributions influence coping procedures, including whether to seek and accept medical treatment. In persons with prodromal HD the relationship between attributions and use of coping strategies for symptoms that interfere with job functioning is unknown.