X-linked myotubular myopathy (XLMTM) is a rare, severe, neuromuscular disorder for which novel treatments are under investigation. This study estimated quality-of-life weights (or utilities) for children with XLMTM. The state that was rated the worst described a child unable to sit and requiring invasive ventilation for≥16 hours a day (utility = -0.07 or -0.27 depending on method used). The state describing a child who can stand and walk and does not require invasive ventilation was the most highly rated state and had a utility of 0.91 or 0.77 (depending on method used).Nine health state vignettes were developed for XLMTM defined in terms of respiratory and motor function based on clinical trial data from parents completing the Assessment of Caregiver Experience with Neuromuscular Disease (ACEND) Domain 1 scale assessing mobility, transfers, sitting, playing, eating, grooming and dressing. These data were supplemented with qualitative data from parent interviews on the daily impact of XLMTM, especially in terms of psychological wellbeing, pain and discomfort, and communication. Seven clinical experts reviewed the draft vignettes for accuracy. Vignettes were rated by members of the UK general public using a time trade-off (TTO) interview and an EQ-5D-5L assessment. This study demonstrated a substantial impact of XLMTM on utility weights.
Keywords: EQ-5D-5L; X-linked myotubular myopathy; gene replacement therapy; health state utilities.