Omalizumab in severe chronic urticaria: are slow and non-responders different?

Summary Background. The response to Omalizumab by patients with severe Chronic Spontaneous Urticaria (CSU), may be rapid, slow, or absent. An early response has been associated with an IgE-mediated auto-allergic pathogenic mechanism, whereas little is known about slow and non-responders. Objective. To compare CSU patients responding slowly or non-responding to Omalizumab. Methods. Forty-six patients showing a slow (n= 23) or absent (n= 23) response to Omalizumab out of a cohort of 170 patients with severe CSU (UAS-7 major 30) were studied. Several baseline clinical and serological parameters were compared in the two groups. Results. Apart from a lower prevalence of atopic diseases (p minor 0.05) and a slightly higher prevalence of thyroid autoimmunity in non-responders, the two groups were similar in terms of clinical and serological features. The majority of patients in both groups showed low baseline total IgE levels. Conclusions. Patients with severe CSU showing a slow response or not responding at all to omalizumab show impressive similarities. It is currently not possible to predict whether patients with severe CSU and low IgE levels will show a slow response or will not respond to anti-IgE treatment.