The Urticaria Activity Score (UAS) is the patient-reported measure of disease activity recommended by the international EAACI/GA2LEN/EuroGuiDerm/APAAACI urticaria guideline for chronic spontaneous urticaria. It was formalised in the 2006 guideline and validated by Mlynek et al. (2008), and its weekly form, the UAS7, is the standard primary endpoint in trials of omalizumab, ligelizumab, remibrutinib and dupilumab in chronic urticaria. Because wheals come and go within hours, a single clinic observation is unreliable, and the score is therefore recorded prospectively by the patient in a daily diary.

Each day the patient scores two items from 0 to 3: the number of wheals over the preceding 24 hours (none; fewer than 20; 20 to 50; more than 50 or large confluent areas) and the intensity of itch (none; mild and not troublesome; moderate and troublesome but not interfering with daily activity or sleep; intense and interfering with daily activity or sleep). The daily UAS is the sum of the two items (0 to 6), and the UAS7 is the sum of seven consecutive daily scores (0 to 42). The wheal and itch items summed over the week form the HSS7 and ISS7 sub-scores (0 to 21 each), which are reported separately in trials.

Two versions exist. The guideline-recommended once-daily UAS7 asks for a single retrospective assessment of the preceding 24 hours, whereas the twice-daily version (UAS7TD) used in the omalizumab registration programme records a morning and an evening score for the preceding 12 hours and averages them. Hollis et al. (2018) showed that the two versions give closely correlated but not identical values, so the same version should be used when a patient is followed over time. This calculator implements the once-daily version. A complete UAS7 requires seven consecutive days; when fewer days have been recorded the calculator projects a weekly score from the mean daily score and flags the result as incomplete.

Disease activity categories were derived by Stull et al. (2017) from pooled omalizumab trial data: 0 urticaria-free, 1 to 6 well-controlled, 7 to 15 mild, 16 to 27 moderate and 28 to 42 severe. The 2022 guideline adopts a UAS7 of 6 or less as the treatment target for well-controlled disease and a UAS7 of 0 as complete response. The minimal important difference is approximately 10 to 11 points: 9.5 to 10.5 in the anchor-based analysis of Mathias et al. (2012) and 11 for the once-daily version in Hawro et al. (2018). Trial and reimbursement criteria in Canada for omalizumab and remibrutinib rely on a documented baseline UAS7, commonly of 16 or more, and on the change achieved on treatment.

The UAS7 measures only wheals and itch. It does not capture angioedema, which is assessed with the separate Angioedema Activity Score, nor overall disease control, which is measured with the Urticaria Control Test. Both of those instruments are copyright of Charite and MOXIE GmbH and require a licence, and neither is reproduced here. The descriptor wording on this page is written in the site's own words from the published criteria and is not the copyrighted diary form of any pharmaceutical sponsor.