Clinically significant differences in patient-reported outcomes evaluations in chronic spontaneous urticaria.

Chronic spontaneous urticaria is a common skin disorder that affects up to 1% of the world population, with more women affected. Its symptoms include repeated occurrence of itchy wheals, angioedema or both, for over 6 weeks. The objective of this review was to highlight the conceptual and practical knowledge for interpreting score changes in patient-reported outcomes (PROs) that have been validated for chronic spontaneous urticaria.

Guidelines recommend assessing PROs as Health-Related Quality of Life, disease activity and disease control to detect the impact of urticaria and the overall treatment effect. In order to have this, it is fundamental to determine the minimal important difference (MID) to evaluate if changes in questionnaire scores represent a perceived improvement or deterioration for patients. MID are collected into two categories, distribution-based and anchor-based.

For most chronic spontaneous urticaria questionnaires, a MID has been defined according to the results of various approaches. The majority of studies analysed in this review used anchor-based methods. The available information regarding MIDs across validated tools for people with chronic spontaneous urticaria helps to interpret measurement scores and allows the implementation of PROs in routine practices.