The most appropriate primary outcomes to design clinical trials on Huntington's disease: meta-analyses of cohort studies and randomized placebo-controlled trials

Total functioning capacity scale in Huntington's disease: natural course over time

BACKGROUND AND OBJECTIVES

The total functioning capacity (TFC) assessment has been integral to Huntington's disease (HD) research and clinical trials, measuring disease stage and progression. This study investigates the natural progression of function in HD, focusing on changes in TFC scores related to age and CAG-repeat length, and evaluates TFC's strengths and weaknesses in longitudinal studies.

METHODS

Using Enroll-HD platform's clinical dataset version 5, including Registry-3, we analysed data from 21,079 participants, with 16,083 having an expanded CAG repeat. Our final analysis encompassed 15,527 patients and 52,457 visits, with TFC scores ranging from 0 to 13.

RESULTS

Alluvial charts show that most individuals maintain maximum functional capacity over time. 3505 individuals experienced change in TFC scores, over the subsequent 4 years, 2224 (64.1%) experienced declining TFC scores, while 661 (18.6%) showed improvement within a year. The remaining 17.3% exhibited stable TFC scores. Age-related changes followed a specific sequence: occupation, household chores/finances, daily living, and care. Longer CAG-repeat lengths were linked to earlier functional decline, with some geographic regions showing earlier losses in specific domains. Reduced penetrance CAG-repeat groups exhibited different trajectories from full penetrance HD participants.

DISCUSSION

When we focus on those who experienced a change in TFC score, the number of HD patients with regained functional capacity is substantial, even considering interrater variability, which may influence outcome assessments in clinical trials. The TFC effectively reflects changes in functional domains as intended. Analysis of the reduced penetrance group suggests potential selection biases in seeking medical attention earlier and for reasons unrelated to HD.

Measuring the functional impact of cognitive impairment in Huntington’s disease

Background

Patients with Huntington’s disease (HD) exhibit a variable predominance of cognitive, behavioral and motor symptoms. A specific instrument focusing on the impact of cognitive impairment in HD over functional capacity is lacking.

Objective

To address the need for a brief and specifically developed HD questionnaire able to capture functional aspects suspected to be sensitive to cognitive impairment.

Methods

We developed and validated the “Huntington’s Disease-Cognitive Functional Rating Scale” (HD-CFRS) in 78 symptomatic carriers of the Huntington’s disease mutation. We also administered the HD-CFRS to a knowledgeable informant to measure the level of agreement. To explore the association between HD-CFRS scores and participants’ cognitive status, we administered objective measures of cognition. Participants were classified as cognitively preserved (HD-NC), as having mild cognitive impairment (HD-MCI), or as having dementia (HD-Dem).

Results

The HD-CFRS showed concurrent validity and internal consistency in the three groups. HD carriers and informants in the HD-NC group obtained similar HD-CFRS scores. However, in patients with mild cognitive impairment and dementia, informers reported greater functional impairment than HD participants. The HD-CFRS total score showed strong correlations with measures assessing cognition.

Conclusions

These findings support the utility of the HD-CFRS as a brief and reliable instrument to measure functional defects associated with cognitive impairment in HD. We believe this questionnaire could be a useful tool both for clinical practice and research.

Motor, cognitive, and functional declines contribute to a single progressive factor in early HD

OBJECTIVE

To identify an improved measure of clinical progression in early Huntington disease (HD) using data from prospective observational cohort studies and placebo group data from randomized double-blind clinical trials.

METHODS

We studied Unified Huntington Disease Rating Scale (UHDRS) and non-UHDRS clinical measures and brain measures of progressive atrophy in 1,668 individuals with early HD followed up prospectively for up to 30 to 36 months of longitudinal clinical follow-up.

RESULTS

The results demonstrated that a composite measure of motor, cognitive, and global functional decline best characterized clinical progression and was most strongly associated with brain measures of progressive corticostriatal atrophy.

CONCLUSIONS

Use of a composite motor, cognitive, and global functional clinical outcome measure in HD provides an improved measure of clinical progression more related to measures of progressive brain atrophy and provides an opportunity for enhanced clinical trial efficiency relative to currently used individual motor, cognitive, and functional outcome measures.