OBJECTIVES: Wilson Disease is a rare disorder in which a mutation of ATP7B causes copper to accumulate in the blood, resulting in liver disease and neurological symptoms. The objective of this research was to confirm the content validity of the Wilson Disease Functional Rating Scale – Patient Report (WDFRS-PR) for use in the Wilson Disease patient population.

METHODS: The WDFRS-PR was developed using results from an online survey and input from experienced Wilson Disease clinicians and is intended to assess the symptoms and impact of Wilson Disease. Mixed concept elicitation and cognitive interviews were conducted to confirm the content, identify any missing concepts, and debrief the draft questionnaire. All interviews were conducted after IRB/ethics approval. Participants had completed the WDFRS-PR prior to interviews.

RESULTS: A total of 29 adult and adolescent patient interviews were conducted, with 15 participants from a clinical survey study participating in cognitive debriefing interviews and 14 participants from an independent qualitative study participating in mixed concept elicitation and cognitive debriefing interviews. Overall, the WDFRS-PR instructions, items, and response options were interpreted as intended and reported to be clear. Participants reported varying levels of experience with concepts in the WDFRS-PR, with anywhere from 27.6% to 65.5% participants reporting that certain concepts (27.6% = more aggression than normal; 65.5% = fatigue) were relevant to them. Results from the 14 concept elicitation interviews helped to further confirm the concepts in the WDFRS-PR along with spontaneous report of new concepts.

CONCLUSIONS: Given the rarity of Wilson Disease, a rigorous yet pragmatic process was undertaken to develop and assess the content validity of the WDFRS-PR. Future research includes comparison of the interview results to an existing conceptual model in Wilson Disease and updates to the WDFRS-PR to reflect patient input. There is also a clinician-administered component to the WDFRS currently in development.