Comparison of Urticaria Activity Score Over 7 Days (UAS7) Values Obtained from Once-Daily and Twice-Daily Versions: Results from the ASSURE-CSU Study

Abstract

Background: The Urticaria Activity Score summed over 7 days (UAS7) assesses the itch severity and hive count in chronic spontaneous urticaria (CSU) using once- or twice-daily diary-based documentation.

Objective: The aim of this study was to evaluate the comparability of twice-daily versus once-daily versions of the UAS and the resulting UAS7 values.

Methods: Data came from the ASSURE-CSU study. The twice-daily and once-daily UAS7 was calculated from morning and evening ratings, as well as from exact 24-h evening ratings of hive count and itch severity, respectively. Three UAS7 scores were computed: UAS7 twice daily (UAS7_TD), UAS7 once daily for maximum itch (UAS7_OD1MAX), and UAS7 once daily for average itch (UAS7_OD2AVG). UAS7 values were assigned to five score bands (0, 1-6, 7-15, 16-27, 28-42), reflecting urticaria-free to severe disease activity. The score values and score band ratios of the UAS7_TD and UAS7_OD versions were compared and assessed for correlation by weighted Cohen's kappa statistics.

Results: Data from 614 patients were analyzed. All three versions of the UAS7 yielded very similar results, with a mean (standard deviation) UAS7_TD, UAS7_OD1MAX, and UAS7_OD2AVG of 17.3 (10.49), 17.7 (8.90), and 16.2 (8.68), respectively. Correlation coefficients between UAS7_TD and UAS7_OD1MAX, UAS7_TD and UAS7_OD2AVG, and UAS7_OD1MAX and UAS7_OD2AVG were 0.94, 0.95, and 0.99, respectively, showing very high positive pairwise correlation. The weighted kappa coefficient, κ (95% confidence interval) was 0.78 (0.75-0.82) for UAS7_TD versus UAS7_OD1MAX, and 0.82 (0.78-0.85) for UAS7_TD versus UAS7_OD2AVG, demonstrating substantial agreement.

Conclusions: The once- and twice-daily UAS7 scores were highly consistent, supporting the use of either version when evaluating CSU activity.