Presentation (CTI)

OBJECTIVES: The Huntington’s Disease Manifest Quality of Life (HD‑mQoL) is a unidimensional, needs‑based patient‑reported outcome measure developed using Rasch Measurement Theory (RMT). While Rasch analysis provides interval‑level measurement, interpretation of logit scores remains challenging. This study aimed to derive clinically meaningful interpretative levels on the Rasch continuum and evaluate their validity using independent indicators of disease and symptom burden.
METHODS: Data from the international validation study of the HD mQoL (N=238 individuals with manifest Huntington’s disease) were analysed. The final 23 item dichotomous scale demonstrated good model fit, unidimensionality, and high reliability (PSI=0.85; Cronbach’s α≈0.91-0.92).Interpretative levels were developed using a Rasch informed approach. Item locations were ordered along the continuum to identify clusters and larger gaps representing transitions in unmet need. Cut points were defined at the midpoints of gaps between adjacent items and refined using the distribution of person measures. Items within each segment were mapped to needs (e.g., autonomy, participation, safety) to derive level descriptions reflecting difficulties beginning to emerge at each level.Levels were evaluated against disease burden (CAP, CAP100, PIN), neuropsychiatric symptoms (PBA), and known‑groups variables (self‑reported disease severity, general health). Exploratory latent profile analysis assessed alignment between empirical patient groupings and Rasch‑derived levels.
RESULTS: Item distribution supported the identification of distinct regions on the Rasch continuum, enabling derivation of a small number of interpretative levels. These levels reflect increasing unmet needs from early limitations in autonomy and activity engagement to broader impairments in social participation and safety. Preliminary findings indicate consistent differentiation across clinical indicators, with higher levels associated with greater disease burden and symptom severity.
CONCLUSIONS: Rasch‑derived interpretative levels provide a robust framework for translating HD‑mQoL scores into clinically meaningful categories. This approach enhances interpretability and supports application in clinical practice, research, and evaluation of treatment outcomes.