Predictors of response to omalizumab and relapse in chronic spontaneous urticaria: a study of 470 patients.

Background Chronic spontaneous urticaria (CSU) is defined as spontaneous occurrence of wheals and/or angioedema for >= 6 weeks. Omalizumab is a monoclonal anti-IgE antibody effective in refractory CSU, but its mechanism of action and markers predictive of response remain not completely defined. Objectives To correlate baseline levels of two proposed biomarkers, total IgE (bIgE) and D-dimer (bD-dimer), and clinical parameters to omalizumab response and to relapses after drug withdrawal. Methods In this retrospective Italian multicentre study, clinical data were collected in 470 CSU patients, and bIgE and bDdimer were measured in 340 and 342 patients, respectively. Disease activity was determined by Urticaria Activity Score 7 (UAS7) at week 1 and 12 after omalizumab starting. Relapses were evaluated during a 2-and 3-month interval after a first and a second course of treatment, respectively. Results bIgE correlated to a good response to omalizumab since levels were significantly higher in responders than nonresponders (P = 0.0002). Conversely, bD-dimer did not correlate to response. There was no correlation between both bIgE and D-dimer and either first or second relapse. Disease duration was significantly longer in patients who experienced either first or second relapse (P < 0.0001 and P = 0.0105, respectively), while baseline UAS7 correlated only to first relapse (P = 0.0023). Conclusions Our study confirms bIgE as a reliable biomarker predicting response to omalizumab in CSU, while it does not support the usefulness of bD-dimer unlike previous findings. CSU duration before omalizumab and baseline UAS7 may be clinical markers of relapse risk.