Validation of the patient benefit index for the assessment of patient-relevant benefit in the treatment of psoriasis.

Empirical evidence of the efficacy of drugs and therapeutic procedures becomes more important in industrial countries. The assessment of patient benefit from the patient's perspective is of particular relevance. The Patient Benefit Index (PBI) for skin diseases is a validated instrument to assess patient-relevant benefit in patients with skin diseases. So far, no instrument for the assessment of patient-relevant needs and benefits in patients with psoriasis has been published. Objective of the study was the validation of an instrument to assess patient benefit in psoriasis treatment. Patient-relevant treatment needs and benefits in psoriasis patients were recorded with the PBI questionnaire in two studies conducted in 2007. Treatment goals and benefits were used to calculate an importance-weighted PBI. Data of n = 2,009 patients in the cross-sectional study and n = 93 patients in the longitudinal study were used to test validity, feasibility and reliability of the PBI. The PBI was feasible with a rate of missing values ≤1.5 % in PNQ and ≤2.0 % in PBQ. The subscales of the PBI were internally consistent (Cronbach's alpha = 0.68-0.87). The PBI showed convergent validity regarding the quality of life, psoriasis area and severity index, and two single questions on treatment benefit used in the longitudinal study. The PBI is a suitable instrument for the assessment of patient-reported benefit in the treatment of psoriasis.