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 (UAS7TD), UAS7 once daily for maximum itch (UAS7OD1MAX), and UAS7 once daily for average itch (UAS7OD2AVG). 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 UAS7TD and UAS7OD 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) UAS7TD, UAS7OD1MAX, and UAS7OD2AVG of 17.3 (10.49), 17.7 (8.90), and 16.2 (8.68), respectively. Correlation coefficients between UAS7TD and UAS7OD1MAX, UAS7TD and UAS7OD2AVG, and UAS7OD1MAX and UAS7OD2AVG 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 UAS7TD versus UAS7OD1MAX, and 0.82 (0.78-0.85) for UAS7TD versus UAS7OD2AVG, demonstrating substantial agreement.
CONCLUSIONS: The once- and twice-daily UAS7 scores were highly consistent, supporting the use of either version when evaluating CSU activity.