Global Real-World Validation of First-Day Urticaria Activity Score (UAS1)

In chronic spontaneous urticaria, the weekly Urticaria Activity Score (UAS7) is a cornerstone patient-reported outcome measure, yet its consistent use in real-world practice can be challenging.

We assessed whether the first-day UAS (UAS1) could serve as a proxy for UAS7 and evaluated its associations with the Urticaria Control Test (UCT) and visual analog scale (VAS) of EuroQol 5-Dimensions (EQ-5D) in a global real-world setting.

We analyzed baseline data from 13,152 patients with chronic spontaneous urticaria across 101 countries enrolled in the international Chronic Urticaria Self-Evaluation app, including 1,520 with complete UAS7 records. Cross-sectional associations among UAS1, UAS7, UCT, and EQ-5D VAS were examined using Spearman correlations, regression models, and diagnostic accuracy metrics, with stratification by phenotype (wheals only vs wheals with angioedema).

We found that UAS1 correlated strongly with UAS7 (r = 0.78; P < .001) across phenotypes. A UAS1 threshold of greater than 3 effectively identified patients with severe disease activity (UAS7 ≥28). Both UAS1 and UAS7 showed moderate to strong inverse correlations with UCT (r = -0.53 to -0.58) and EQ-5D VAS (r = -0.47 to -0.54), whereas UCT and EQ-5D VAS had positive correlations (r = 0.46). These relationships were consistent across symptom subgroups.

The UAS1 demonstrates strong validity as a pragmatic proxy for UAS7 and meaningfully aligns with measures of disease control and quality of life. When the full UAS7 is unavailable owing to missing days (as frequently occurs in routine practice or real-world evidence studies) UAS1 may serve as a validated proxy to estimate disease activity and support treat-to-target goals of complete control and normal life.