Validation and response to treatment of a pruritus self-assessment tool in patients with moderate to severe psoriasis

Background: Pruritus is a common symptom of psoriasis. In many clinical trials of psoriasis treatments, severity of pruritus is a patient-reported outcome. Objective: We sought to evaluate a patient-reported pruritus self-assessment tool using data from clinical trials of a tumor necrosis factor blocker. Methods: The validity of the patient-reported 6-point pruritus assessment tool (0 = none to 5 = severe) was determined using data from a phase III trial of etanercept, a tumor necrosis factor blocker. The performance of the pruritus assessment tool was then evaluated using data from two large etanercept trials. Results: The pruritus assessment tool was validated and deemed to have good test-retest reliability (kappa coefficient = 0.71; 95% confidence interval = 0.62-0.80) and responsiveness (standardized response mean = 1.28; effect size = 1.63, responsiveness statistic = 1.54). Improvements in pruritus scores correlated with improvements in Psoriasis Area and Severity Index after 8 weeks of etanercept therapy in two phase III trials. Limitations: The pruritus assessment is validated only for patients with moderate to severe plaque psoriasis, and may not be applicable to other patient populations. Conclusions: The pruritus assessment tool is a valid measurement of pruritus intensity in patients with moderate to severe plaque psoriasis and can discriminate between patients on and off treatment.