Health State Utilities Associated with X-Linked Retinitis Pigmentosa in the United Kingdom

OBJECTIVES: X-linked retinitis pigmentosa (XLRP) is a rare inherited retinal disease characterized by impairment in visual field (VF) and visual acuity (VA) with continuous progression of disease leading to blindness. Gene therapies for XLRP are currently under investigation, and health state utilities will be needed for use in cost-utility analyses to examine the value of these treatments. This study aimed to estimate health state utilities associated with XLRP severity.

METHODS: Eleven health state vignettes depicting combinations of impairment in VF and VA associated with XLRP were developed based on a literature review, clinicians’ input, and interviews with caregivers and patients with XLRP. Vignettes included text describing the impairment in VF/VA, night blindness, the impact of XLRP, and two images representing the combination of VF and VA impairment for each health state. The images depicted a street scene and a group of three people. Health states were valued in time trade-off interviews with general population respondents from three locations in the UK.

RESULTS: A total of 245 participants completed interviews (51.0% male; mean age = 41.4 years; 80 from Newcastle; 85 from London; 80 from Edinburgh). In a ranking task, participants preferred health states with less severe impairment, and this pattern of preference was reflected in the mean health state utilities. Mean (SD) utilities ranged from 0.900 (0.121) for health state A with no VA impairment and mild VF impairment to 0.271 (0.478) for blind.

CONCLUSIONS: In general, utilities followed expected patterns. Health states with less severe impairment in VF and VA had higher mean utilities than those with more severe impairment. The relatively low utilities highlight the substantial impact of XLRP on quality of life. The health state utilities estimated in this study may be useful in cost-effectiveness models evaluating treatments for XLRP.