The minimal important difference for measures of urticaria disease activity: Updated findings.

BACKGROUND: The Urticaria Patient Daily Diary (UPDD) is a validated patient-reported outcome that captures key measures of urticaria disease activity. OBJECTIVE: To update estimates of the minimal important difference (MID) for urticaria disease activity measures in the UPDD, including the weekly itch severity score, weekly number of hives score, weekly average size of largest hive score, and the composite measure of itch severity and number of hives over 7 days, or urticaria activity score 7 (UAS7). METHODS: A total of 975 subjects with chronic idiopathic urticaria from three randomized, double-blind, placebo-controlled studies completed the UPDD and other patient-reported outcome assessments (the Dermatology Life Quality Index, Medical Outcomes Study Sleep Scale, the Chronic Urticaria Quality-of-Life Questionnaire, the EuroQoL-5 Dimension Questionnaire) multiple times. MIDs were estimated through a combination of distribution- and anchor-based methods. RESULTS: MID estimates ranged from 4.5 to 5.0 for the weekly itch severity score, 5.0 to 5.5 for weekly hives count score, 9.5 to 10.5 for the UAS7, and 4.0 to 4.5 for the weekly size of the largest hive score. CONCLUSION: This analysis provided confirmation of the previous MID estimates for the urticaria disease activity measures in the UPDD.