Monitoring of omalizumab therapy by measuring free IgE using a bedside immunoassay.

Abstract

The monoclonal anti-IgE antibody omalizumab is used as add-on therapy for improved asthma control in patients with severe persistent allergic bronchial asthma. The aim of the study was to examine the effectiveness of omalizumab and to demonstrate the hitherto unavailable possibilities for treatment monitoring by means of a bedside immunoassay. In the prospective longitudinal study, 9 patients aged 8 to 15 years with severe persistent allergic asthma received add-on treatment with omalizumab. Besides the parameters of general physical examination, recordings of exacerbation rate, asthma control and lung function (FEV1), and total IgE concentrations in serum were determined after 6 and 12 months; free IgE was measured using the Milenia QuickLine immunoassay. The mean duration of treatment was 56 ± 7.5 months. After 12 months, omalizumab showed good tolerability and effectiveness with a reduced exacerbation rate, a significant improvement of asthma control (ACT; p < 0.001) and FEV1 (p < 0.01). Already after six months of therapy, a significant reduction in total IgE from 1253 ± 407 IU/mL to 466 ± 120 IU/mL (p < 0.01) was observed. Free IgE levels were below the detection limit in all patients during treatment with omalizumab, even following dose reduction; they increased only after cessation of the treatment. Our data 1) confirmed good therapeutic effectiveness of omalizumab in patients with severe persistent asthma and 2) indicated that a quick and easy-to-use immunoassay to measure free IgE together with thorough clinical assessment may be a potential instrument for monitoring omalizumab treatment.