Goals and benefits in topical treatment for psoriasis: development and pilot validation of a patient-reported outcomes tool, the Patient Benefit Index for Topical Treatment (PBI-TOP).

Background: Topical agents are an essential component of psoriasis therapy.

Objectives: To develop a new version of the patient-reported Patient Benefit Index assessing the importance and achievement of treatment goals in topical psoriasis therapy in adult patients (PBI-TOP).

Methods: Through semi-structured interviews, focus groups and free-text questionnaires, patients reported their needs in topical treatment. Based on qualitative content analysis, items were developed by a consensus group and were refined in cognitive debriefing interviews. A pilot validation assessed the PBI-TOP and convergent criteria [Dermatology Life Quality Index (DLQI); Psoriasis Area and Severity Index (PASI); affected Body Surface Area (BSA)].

Results: Thirty patients (26-72 years, mean 47; 60% male) reported various treatment goals relating to the themes 'effectiveness' and 'characteristics of the preparation'. Twenty patients took part in cognitive debriefings (22-84 years, mean 50.6, 50% male). There were 154 patients who participated in the pilot validation (18-85 years, mean 46.9, 63.6% male). An importance-weighted total score on overall effectiveness and three subscales based on exploratory factor analysis were defined: effectiveness on symptoms, effectiveness on quality of life (QoL), and characteristics of the preparation. All scores showed excellent internal consistency (α > 0.9). The global effectiveness score correlated significantly with DLQI (r = -0.41), PASI (r = -0.32) and BSA (r = -0.22). The effectiveness subscales (symptoms; QoL) correlated significantly with DLQI (r = -0.41; -0.32) and PASI (r = -0.27; -0.33). The score on characteristics of the preparation correlated significantly with the DLQI (r = -0.34).

Conclusions: The PBI-TOP showed good feasibility and favourable psychometric characteristics in this pilot validation.