Meaningful and measurable health domains in Huntington’s: Large-scale validation of the Huntington’s Disease health-related Quality of Life questionnaire (HDQoL) across severity stage

Objectives: While health-related quality of life is key for patients with long-term neurodegenerative conditions, measuring this is less straightforward and complex in Huntington’s disease. This study aimed to refine and validate a fully patient-derived instrument, the Huntington’s Disease health-related Quality of Life questionnaire (HDQoL), and to elucidate health domains that are meaningful to patients’ lived experience.

Methods: Five-hundred and forty-one participants, from pre-manifest to end-stage disease completed the HDQoL, together with generic quality of life measures, and in-person motor, cognitive and behavioural assessments. The psychometric properties of the HDQoL were examined using factor analysis and Rasch analysis.

Results: Four HDQoL domains emerged reflecting the classical triad of HD features - they were Physical-Functional, Cognitive, and two different behavioural aspects i.e. Mood-Self domain, as well as a distinct Worries domain. These domains clarify the behavioural sequelae as experienced by patients, and all showed good to excellent internal consistency. Known groups analyses illustrated significant and graded changes in clinical assesments and corresponding HDQoL domains across severity levels. Convergent and discriminant validity was demonstrated by the expected pattern of correlations between specific HDQoL domains and corresponding domain-relevant clinical assessments as well as patient-reported measures. The data demonstrate robust support for the refined HDQoL across disease stages.

Conclusions: The HDQoL with its two distinct behavioural domains of Mood-Self and of Worries, as well as a Physical-Functional and a Cognitive domain, is a relevant, reliable and valid patient-derived instrument to measure the impact of Huntington’s disease across all severity stages.