Study materials

A semi-structured interview guide (Supplementary file 1) was developed based on the published literature on the HRQoL of individuals with DMD and through consultation with clinical experts in the UK and Germany and two patient advocacy groups (PAGs) in the UK (Muscular Dystrophy UK and Action Duchenne). The clinical experts included two medically/surgically trained clinicians, with a combined clinical experience of more than 10 years, and medical affairs/clinical development experience of more than 15 years, with a focus in muscular dystrophies. The PAG input included feedback from a caregiver of an individual with DMD. The interview guide comprised mainly of open-ended questions on the individual with nmDMD’s diagnosis and symptoms, as well as the impacts on their daily life, HRQoL, and the impacts on their caregiver (not included in this paper). These questions were asked in relation to their experience both before and since their son started taking ataluren.

A background questionnaire was developed to collect socio-demographic information and information on the individual with nmDMD’s diagnosis and treatments (Supplementary file 2). This included questions about motor function, which allowed individuals to be characterised into one of three ambulatory health states according to the natural history model developed by the University of Leicester (early ambulatory: can rise from supine, stand and walk 10 m; late ambulatory: can stand and walk 10 m; transfers: can stand) [12]. Throughout this paper we use the term ambulatory to refer to these three health states.

Caregivers also completed the DMD-QoL v2 Proxy, a newly developed questionnaire designed to assess the quality of life of individuals with DMD from the perspective of caregivers [13]. As the final version of the questionnaire was not yet available at the point the study was conducted, a draft version was used. This version had 27 items, each asking about an aspect of quality of life in the last week (e.g. ‘In the last week he was in pain’). All items were scored on a 4-point scale from 3 = never to 0 = all of the time, and there was also a not applicable option. Mean total scores (range 0–81) and mean average scores (range 0–3) were calculated based on scoring instructions from the questionnaire developers, with higher scores indicating better quality of life.