Psoriatic arthritis (PsA) is a seronegative inflammatory arthritis found in up to 5 to 42% of patients with psoriasis. As current instruments do not fully capture health-related quality of life (HR-QOL) in PsA from the patient's perspective, we piloted a novel application of "willingness-to-pay" (WTP) as a Patient Reported Outcome to measure the relative impact of PsA in 8 domains of HR-QOL.
Fifty-nine PsA patients were interviewed on 8 WTP HR-QOL domains (physical, emotional, sleep, work, social, self-care, intimacy, and concentration). Participants were asked to rank the 8 domains of health in order of HR-QOL impact. In each domain, participants were asked whether PsA affected that domain, whether they were willing to pay for a cure in that domain, and the amount they were willing to pay. Median WTP amounts were compared with the proportion of participants affected by and willing to pay in each domain. Responses in US dollars were interpreted as strength of preference rather than absolute monetary values.
The majority of participants were white (98%), > or =45 years of age (70%), insured (98%), and earned >$65,000/yr (66%). The physical domain was most affected by PsA; intimacy and concentration were ranked lowest. Participants reported a wide range of WTP amounts ($0 to $1,000,000), and median WTP amounts were highest in the physical, work, sleep, and self-care domains. Related domains elicited median WTP amounts that were highly correlated. No significant differences in median WTP amounts were found across ages, genders, and income levels for the different domains.
WTP is a novel quantitative patient-perspective measure that is comprehensible and feasible to administer in PsA patients. It represents a unique tool for capturing the complex manifestations of PsA and its impact on the individual, allowing the quantification of specific HR-QOL parameters and providing the potential for comparison across various disease processes in a given individual.