Basophil FcɛRI expression is linked to time to omalizumab response in chronic spontaneous urticaria

To the Editor: Omalizumab has demonstrated excellent efficacy for the treatment of chronic spontaneous urticaria (CSU) in several randomized clinical trials and real-world studies.1,2 As a monoclonal anti-IgE antibody, omalizumab prevents IgE binding to the high-affinity IgE receptor (FcɛRI) on the surface of basophils and mast cells, resulting in a significant reduction in FcɛRI levels in these cells and, therefore, in their capacity to respond to allergen exposure.3 In this regard, the potential for predicting clinical outcomes during anti-IgE therapy based on basophil allergen response has been investigated in several studies mainly focused on allergic respiratory diseases.4 In CSU, meanwhile, it has been recently demonstrated that the modulation of the basophil FcɛRI expression plays a key role in the clinical improvement observed during omalizumab therapy.3,5 Thus, a significant drop in the basophil FcɛRI expression is immediately observed after the first dose, which is maintained throughout the duration of the treatment.5 Although this phenomenon seems to occur very soon after starting treatment, timing to satisfactory clinical response to omalizumab can be highly variable. [...]a positive correlation was found between levels of total serum IgE and baseline FcɛRI expression (Pearson correlation coefficient r = 0.355; P = .018; Fig 1, C). [...]according to our analysis, baseline FcɛRI expression may also be associated with the time to response to omalizumab. [...]patients with very high baseline levels might be more likely to achieve an early therapeutic response. To ensure consistency in the analysis, the same investigator processed and analyzed all samples and 2 independent researchers correlated the levels of basophil FcɛRI expression and the clinical scores.Autologous serum skin test The ASST was performed as previously described.E1 Briefly, venous blood was taken before the first administration of omalizumab.