Variability in total serum IgE over 1 year in severe asthmatics

Abstract

Abstract Background Immunoglobulin E (IgE) is the treatment target of omalizumab, a monoclonal antibody indicated in the treatment of severe allergic asthma. Long-term variability of serum total IgE (sIgEtot) in asthmatics remains poorly documented. Methods In this prospective study, sIgEtot levels were measured over 1 year at 7 time points in 41 severe asthmatics treated with high-dose of inhaled corticosteroids and long-acting β2 agonists. 33 patients were atopic based on at least one positive RAST to common aeroallergens. Patients were divided into three groups according to their baseline sIgEtot level: low ( 700 IU/mL; n = 11). Patients also completed the six-item Juniper Asthma Control Questionnaire (ACQ6). The sIgEtot variability and factors predictive for this variability were studied, as well as ACQ6 outcomes. Results The variation in sIgEtot level was mostly the consequence of between patient-variability, which represented 96%, 71% and 96% of the total variability in the low, intermediate and high sIgEtot subgroups, respectively. The residual within-patient variability was therefore limited. In 10/41 patients, sIgEtot levels increased or decreased, for at least one visit, beyond the predefined range of the subgroups to which they were assigned ( 700 IU/mL). There was a significant but weak correlation between sIgEtot and ACQ6 score over all time points (r = 0.15, p = 0.02), but sIgEtot failed to associate with severe exacerbation. sIgEtot decreased by 3% with any additional year of age for the whole group (p = 0.01) and increased by 5% per one unit of allergen exposure score in atopic patients (p = 0.002). Conclusion In severe asthmatics, limited within-patient variability of sIgEtot levels was observed over 1 year as opposed to marked between-subject variability. sIgEtot decreases with age. Variation in sIgEtot weakly associates with asthma control but not with exacerbation.

Keywords

• Asthma
• IgE
• Variability