OBJECTIVES : Innovative assessments are needed for clinical trials of Duchenne muscular dystrophy (DMD), a rare, fatal, degenerative neuromuscular disease. The DMD-Specific Measures of Physical Functioning: Video Assessments are performance-based measures that require a caregiver to record 6 short videos of their child performing physical activities using a smartphone app. We developed and implemented a standardized process to better understand caregivers’ perceptions of the quality, feasibility, and validity of this measurement approach.

METHODS : One week prior to cognitive debriefing in-person interviews, primary caregivers were asked to review training materials, download the app, and record and submit the Video Assessments. Two independent raters, including a qualitative interviewer, reviewed the submitted videos using a checklist to ensure training materials were followed correctly. During the interview, caregivers were asked to provide feedback on the appropriateness of the physical activities recorded, comprehension of the training materials, ease of use of the app, and feasibility of recording the videos.

RESULTS : All 4 caregivers were mothers of ambulatory DMD patients aged 9-12 years. Raters found that all caregivers correctly used the app; 3 of 4 caregivers correctly followed instructions for all activity videos. One caregiver misunderstood instructions on 2 activities. Caregivers found the training materials and app easy to understand, and reported the videos accurately captured their child’s physical functioning. Caregiver feedback informed recommendations for improvements to the app and training materials to optimize overall functionality and clarify the instructions.

CONCLUSIONS : Pre-work by caregivers to follow and implement training materials, record patient activities, and use the app, with a scientific, clinical standardized review, provided valuable information. Ensuring that caregivers completely understand the process of recording videos reduces the risk of biases in the recording of physical activities that could confound ratings of disease progression and/or the impact of treatment.