How to weight patient-relevant treatment goals for assessing treatment benefit in psoriasis: preference elicitation methods vs. rating scales.

In psoriasis, several patient-relevant treatment goals must be met to be able to consider a treatment beneficial. To assess treatment benefit, the validated questionnaire Patient Benefit Index (PBI) can be used. Its global score summarizes the degree of patient-relevant treatment goals achieved after treatment, weighted by their individual importance on rating scales. These treatment goals have empirically been assigned to five dimensions. While the weighting procedure of the PBI provides information about the importance patients attach to treatment goals on a rating scale from 0 to 4, methods of preference elicitation provide information on how patients would trade off certain treatment goals against each other. However, since the treatment goals defined in the PBI often overlap conceptually, the dimensions of the PBI might be more suitable for exploration in preference elicitation methods. We used an analytic hierarchy process (AHP) and a discrete choice experiment (DCE) to generate preference-based importance weights for the PBI dimensions, and compared these weights to those derived from the rating scales. We were further interested in the effect of importance weights on the calculation of the PBI score. A total of 120 patients with psoriasis completed a questionnaire at baseline, including AHP, DCE and the rating scales, and at follow-up, regarding the attainment of treatment goals, to calculate the PBI score. In contrast to the results derived from the average rating scores, use of AHP and DCE resulted in both similar importance weights and rankings of dimensions. Presumably, patients rated treatment goals differently than the respective dimension they belong to. However, the differently calculated importance weights led to similar values of the PBI score. Our findings nevertheless provide clear evidence that, regardless of the method used, the importance of treatment goals differs between psoriasis patients, and this should be reflected in treatment decisions.