2×4 Rule and low IgE predict poor response to Xolair in urticaria

Based on these two findings, nonresponse to omalizumab within the first 12 weeks of treatment may be best assessed by applying the “2 x 4 rule”:

• When baseline IgE levels fail to double within the first 4 weeks of treatment, nonresponse needs to be expected. The “2 x 4 rule” may be especially helpful in patients with low IgE.
• One of three patients with low IgE, in our study, failed to respond to omalizumab by week 12 of treatment.