The Urticaria Activity Score-Validity, Reliability, and Responsiveness.

BACKGROUND: Chronic spontaneous urticaria is characterized by fluctuating symptoms. Its activity is assessed with the urticaria activity score (UAS). Two versions of the urticaria activity score used for 7 consecutive days (UAS7) are available: (1) The guideline-recommended UAS7, with once-daily documentation, and (2) the UAS7TD , with twice-daily documentation.

OBJECTIVE: To better characterize both UAS7 versions with regard to their validity, reliability, sensitivity to change, minimal important difference (MID), and smallest detectable change (SDC).

METHODS: One hundred thirty adult patients with chronic spontaneous urticaria completed both UAS7 versions, the Patients Global Assessment (PatGA) of disease activity, the Urticaria Control Test (UCT), the Chronic Urticaria Quality of Life Questionnaire, and the Dermatology Life Quality Index before and after the initiation of omalizumab therapy. Physicians completed a Physician Global Assessment of disease activity.

RESULTS: The UAS7 and the UAS7TD showed high correlation with the activity anchor PatGA (r = 0.568, P < .001 and r = 0.605, P < .001) and the UCT (r = -0.580, P < .001 and r = -0.585, P < .001). The wheal and pruritus scores of the UAS7 and the UAS7TD exhibited respectable internal consistency and, in each UAS7 version, correlated well with each other (Cronbach α = 0.78, r = 0.640, P < .001, and Cronbach α = 0.77, r = 0.626, P < .001). Changes in the UAS7 and UAS7TD correlated well with PatGA changes (r = 639, P < .001, and r = .763, P < .001) and with UCT changes (r = -0.642, P < .001, and r = -0.703, P < .001). The MID was 11 for the UAS7 (SDC = 12) and 12 for the UAS7TD (SDC = 11).

CONCLUSIONS: The UAS7 and UAS7TD show good and comparable clinimetric properties, including good sensitivity to change, and similar MIDs.