OBJECTIVES:   Specific ranges of scores reflecting patient severity or changes in severity have not been established for average daily urticaria activity summed over 7 days (UAS7; range=0-42), a common measure for assessing CSU disease activity. This study evaluates whether five non-overlapping health states derived from the continuous UAS7 score can discriminate between patients with different severities of urticaria and are reproducible across multiple studies.  METHODS:   Data come from three randomised, double-blind, placebo-controlled Phase III clinical trials evaluating the effect of omalizumab on symptoms of patients with refractory CSU. Five CSU health states were defined: Urticaria-Free (UAS7=0); Well-Controlled Urticaria (UAS7=1-6); Mild Urticaria (UAS7=7-15); Moderate Urticaria (UAS7=16-27); Severe Urticaria (UAS7=28-42).  Comparison variables included the Dermatology Life Quality Index (DLQI), a 10-item dermatologic QoL instrument (range=0-30; higher scores=greater QoL impairment); patient diary questions asking about sleep and activity interference; presence of angioedema; and number of diphenhydramine 25mg pills taken in previous 24 hours. Analyses established whether different UAS7 health states showed different values on comparison variables. Analyses were replicated across the trials at baseline and weeks 12, 24, and 40 (ASTERIA I and GLACIAL) and baseline and weeks 12 and 28 (ASTERIA II). RESULTS:   Mean values for comparison variables were lowest (zero or very close to zero) for patients who were Urticaria-Free and highest for those with Severe Urticaria.  For Well-Controlled and Mild Urticaria comparison variable values increased. Larger increases in values occurred for Moderate and Severe Urticaria.  Changes in categorical health state severity were highly related to categorical changes in DLQI (p<0.001 for all trials and time points). CONCLUSIONS:   Categorical UAS7 health states show meaningful differences in mean values on comparison variables and are highly related to established levels of effect on dermatological QoL.  Categorical UAS7 health states could be informative about subgroups for economic models and useful for clinical practice.