Surface plasmon resonance analysis of free IgE in allergic patients receiving omalizumab (Xolair).

The diagnosis of human allergic disease involves an initial clinical history based association of allergic symptoms with an allergen exposure. This is followed by confirmation of sensitization (IgE antibody positivity) with skin test, serology or provocation testing. Once diagnosed, the allergic individual can be managed using one or several modalities that involve allergen avoidance, pharmacotherapy, allergen immunotherapy and anti-IgE therapy. This report examines Law of Mass Action considerations for the design of immunological methods which permit the quantification of free (non-Omalizumab bound) IgE in the serum of patients receiving anti-IgE therapy. The rationale for and design and performance of a surface plasmon resonance assay for the detection of "free" IgE (unbound with anti-IgE) is presented as an alternative to microtiter plate based ELISAs.