Calculating the 7-Day Urticaria Activity Score (UAS7)
The UAS7 is calculated by having patients score both wheal count and pruritus intensity once daily for 7 consecutive days, then summing all 14 individual scores (7 days × 2 parameters) to yield a total score ranging from 0 to 42 points. 1
Daily Scoring Method
Each day, patients assign two separate scores:
Wheal Score (0-3 points daily)
- 0 points: No wheals 1
- 1 point: Mild (<20 wheals per 24 hours) 1
- 2 points: Moderate (20-50 wheals per 24 hours) 1
- 3 points: Intense (>50 wheals per 24 hours or large confluent areas) 1
Pruritus Score (0-3 points daily)
- 0 points: None 1
- 1 point: Mild (present but not annoying or troublesome) 1
- 2 points: Moderate (troublesome but does not interfere with normal daily activity or sleep) 1
- 3 points: Intense (severe pruritus sufficiently troublesome to interfere with normal daily activity or sleep) 1
Weekly Calculation
Sum the daily scores (wheal + pruritus) across all 7 days to obtain the UAS7, with a maximum possible score of 42 points. 1 Each individual day contributes 0-6 points to the weekly total. 1
Once-Daily vs. Twice-Daily Documentation
The guideline-recommended version uses once-daily documentation, typically completed in the evening to capture the entire 24-hour period. 2, 3 A twice-daily version (UAS7TD) exists with morning and evening ratings, but research demonstrates both versions yield highly comparable results with correlation coefficients of 0.94-0.95 and substantial agreement (weighted kappa 0.78-0.82). 3 Either version is acceptable, though once-daily evening documentation is the standard approach. 2, 3
Clinical Interpretation
The UAS7 should be used at baseline and every follow-up visit to assess disease activity and guide treatment decisions. 1, 4 The minimal important difference (MID) is approximately 10-12 points, meaning changes of this magnitude represent clinically meaningful improvement or worsening. 2, 5 Score bands typically classify disease severity as: urticaria-free (0), well-controlled (1-6), mild (7-15), moderate (16-27), and severe (28-42). 3
Common Pitfalls
Ensure patients understand that wheal counts refer to the number present during the worst 24-hour period each day, not cumulative counts throughout the day. 1 The pruritus score should reflect the overall severity for that day, not just the worst moment. 1 Patients must complete the diary prospectively for 7 consecutive days rather than retrospectively, as recall bias significantly reduces accuracy. 1, 4