Some patients (30%) with allergic asthma treated with anti-IgE (Xolair) do not become symptom free. Better criteria for response assessment than allergy skin tests or IgE determination are needed. Omalizumab binds to Cε3 region of IgE.
The role of IgE and mast cells in allergy. Image source: Wikipedia, public domain.
In this study the amount of cat allergen-specific IgE antibody was measured as a percentage of total IgE in cat allergic patients treated with the recommended doses of Xolair. Results were measured as changes in basophil allergen threshold sensitivity.
The authors concluded that significant efficacy of anti-IgE (Xolair) treatment can be predicted when Xolair decreases the amount of cat allergen-specific IgE to less than 1% of total IgE. Xolair effect was insufficient if cat allergen-specific IgE was more than 3-4% of total IgE.
The size of the disease relevant IgE antibody fraction in relation to 'total-IgE' predicts the efficacy of anti-IgE (Xolair) treatment. Johansson SG, Nopp A, Oman H, Ankerst J, Cardell LO, Grönneberg R, Matsols H, Rudblad S, Strand V, Stålenheim G. Allergy. 2009 Apr 14. [Epub ahead of print]