Development and validation of the first needs-based quality of life measure for individuals with manifest Huntington’s disease

Background Huntington’s disease (HD) is a progressive, hereditary neurodegenerative disorder currently without curative treatments, thus making quality of life (QoL) an important outcome for clinical care and therapeutic evaluation. Existing HD-specific patient-reported outcome measures (PROMs) do not adequately capture the experiences of individuals with manifest HD. This study presents the multinational development and validation of the Huntington’s Disease Manifest Quality of Life measure (HD-mQoL), the first needs-based, disease-specific PROM for assessing QoL in individuals with manifest HD. Methods Development followed three stages: (1) generation of measure content and translations; (2) testing of face and content validity; and (3) psychometric validation using data from a large international survey analysed with Rasch Measurement Theory (RMT) and Classical Test Theory (CTT). Results The measure was completed by 238 individuals with manifest HD from the Czech Republic, Germany, Ireland, Italy, and the UK (59% male; age range 20–83 years). Rasch analysis reduced 49 items to a final set of 23, demonstrating good model fit (item–trait interaction χ 2 = 0.391), unidimensionality, no differential item functioning, no local dependency, and excellent reliability (Cronbach’s α = 0.91 at timepoint 1, 0.92 at timepoint 2; test–retest r = 0.87). The final measure showed minimal floor and ceiling effects and correlated moderately to strongly with relevant Nottingham Health Profile domains. HD-mQoL scores effectively differentiated subgroups by self-rated disease severity and general health (p < 0.001). Conclusions The HD-mQoL is a robust, needs-based measure of QoL, suitable for international use in clinical practice and trials assessing treatment value from the patient’s perspective.