Background Chronic spontaneous urticaria (CSU), also known as chronic idiopathic urticaria, may produce hives, itch, and angioedema. The Urticaria Activity and Impact Measure (U-AIM) is a newly developed 9-item patient-reported measure designed for use in routine clinical practice to assess CSU activity and impact during the previous 7 days. Objective To evaluate validity, responsiveness, and clinically meaningful change of the U-AIM. Methods Data from a 24-week, open-label, single-arm period of a randomized, placebo-controlled study of omalizumab were used to assess the psychometric properties of U-AIM items for itch, hives, and angioedema. Results A total of 206 patients (75% female; mean age, 44.6 years) were enrolled. At baseline, U-AIM results included prevalent severe itch (55%) and more than 12 hives (67%), angioedema (15%), and bother by itch (84%), hives (84%), and angioedema (49%). The Urticaria Patient Daily Diary (UPDD) mean weekly scores were 15.4 (itch severity), 16.8 (number of hives), and 32.2 (Urticaria Activity Score [UAS7]). At baseline, week 12, and week 24, U-AIM itch and hives items and UAS7 proxy scores (the sum of itch severity and number of hives during 7 days) demonstrated strong correlation coefficients with their corresponding measures from the UPDD (itch severity: 0.634–0.806; hives number: 0.735–0.843; UAS7 proxy: 0.724–0.852). Changes in U-AIM scores differentiated patients by their perspective of symptom improvement. Meaningful change thresholds were established for itch severity and number of hives scores (range, 0.8–1.0 for both) and the UAS7 proxy score (range, 10.5–12.5). Conclusion The U-AIM is valid and responsive to change and may help clinicians monitor CSU activity and track treatment effectiveness.
