Abstract
INTRODUCTION: RLBP1 RP is an autosomal recessive form of retinitis pigmentosa (RP), characterized by night blindness, prolonged dark adaptation, constricted visual fields and impaired macular function. This study aimed to better understand the patient experience of RLBP1 RP and evaluate the content validity of existing patient reported outcome (PRO) instruments in this condition. METHODS: Semi-structured concept elicitation and cognitive debriefing interviews were conducted with RLBP1 RP patients in Canada and Sweden. Interviews started with open-ended concept elicitation questioning, and then patients were cognitively debriefed on The National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25), the Low Luminance Questionnaire (LLQ) and four light/dark adaptation items of the Visual Activities Questionnaire (VAQ). Qualitative interviews were also conducted with three expert clinicians. Anonymized, verbatim transcripts were analyzed using thematic analysis. RESULTS: Twenty-one patients were interviewed (Canada n = 10; Sweden n = 11). Symptoms reported included night blindness (n = 21), difficulty adapting to changes in lighting (n = 21) and difficulties seeing in bright lighting (n = 18). Patients experienced substantial impacts on daily activities (n = 21) and physical functioning (n = 17). Patients had difficulty interpreting and selecting a response for some items in the NEI VFQ-25 and LLQ. Some items were not relevant to patients' disease experience. There were both gaps and overlaps in the conceptual coverage of the instruments. CONCLUSIONS: Visual impairment due to RLBP1 RP has a substantial impact on physical functioning and daily activities. To adequately assess all important symptoms and associated functional impacts in RLBP1 RP, it is recommended to either modify one or more existing instruments or to develop a new non-syndromic RP specific instrument.