Presentation (CTI)

OBJECTIVES: Existing patient-reported outcome measures in Chronic Inducible Urticaria (CIndU) are not suitable for use across different subtypes. A combination of qualitative and psychometric studies were conducted to validate a novel measure of triggers, symptoms, and impacts, suitable for assessing the most bothersome symptom (MBS) across different CIndU subtypes in clinical trials.
METHODS: The USDD comprises of 12 items assessing exposure and avoidance of triggers, severity of hives and symptoms (itch, pain, and burning), impact of symptoms on daily activities and sleep, rescue-medication use, and healthcare provider contacts. Standalone qualitative interviews, combining concept elicitation and cognitive debriefing, were conducted in adults with symptomatic dermographism, cold urticaria, and cholinergic urticaria. Psychometric analysis was conducted using data from a phase 3 study to assess reliability, construct validity, responsiveness, and meaningful change thresholds.
RESULTS: Interviews confirmed that the USDD captures relevant and meaningful aspects of disease experience across the 3 CIndU subtypes. Participants experienced different combinations of itch, pain, and burning and most were able to distinguish these as distinct sensations, supporting the MBS approach. The USDD was confirmed to be relevant and easy to understand and complete, supporting content validity. Psychometric findings showed that weekly USDD scores had moderate-to-strong correlations with related measures (|r| ≥ 0.3), demonstrated strong test-retest reliability (screening to baseline intraclass correlation coefficients ≥ 0.70), discriminated between known groups, and were able to show change over time. Estimates of meaningful within-patient change thresholds for the weekly MBS score ranged from 2.0-4.3 points for symptomatic dermographism, 1.7-5.0 points for cold urticaria, and 2.0-3.0 points for cholinergic urticaria.
CONCLUSIONS: The totality of evidence supports the USDD as a fit-for-purpose patient-reported outcome measure for CIndU. The MBS-based scoring approach accommodates heterogeneity across subtypes and captures outcomes that matter to patients, supporting its use in clinical development and endpoint evaluation.