To evaluate the relationship between the cumulative level of respiratory allergen specific immunoglobulin E (sIgE) and the reactivity of omalizumab in severe asthma.

All of 106 0patients with severe asthma who received omalizumab in our hospital from October 2020 to June 2022 were retrospectively included. According to the International Classification of Diseases, there were 57 cases of allergic asthma, 40 cases of non-allergic asthma and 9 cases of mixed asthma. Standard empirical allergy diagnosis (anaphylaxis memory, skin prick test, total IgE and allergen sIgE determination by traditional route), blood eosinophilic count, Phadiatop™ test for measurement of respiratory allergen sIgE accumulation levels were performed. 34 patients with allergic asthma were treated with omalizumab for 12 months to evaluate the clinical efficacy.

Accumulative levels of respiratory allergen sIgE determined by Phadiatop™ testing were significantly higher in patients with allergic and mixed severe asthma than in patients with non-allergic asthma (P<0.001). The area under the subject operating characteristic curve to distinguish allergic asthma from non-allergic asthma was calculated as 0.891±0.038, and the optimal cutoff value was 0.24 kAU/L. Phadiatop™ test ≥0.24 kAU/L was regarded as positive, and the prevalence of allergic asthma diagnosed by positive anaphylactic memory+ Phadiatop™ test was 84.21% (48/57), slightly higher than that diagnosed by positive anaphylactic memory + sIgE (56.14%, 32/57), P=0.001. Among 34 patients with allergic asthma who received omalizumab treatment, 8 patients had good symptom control. Phadiatop™ test ≥1.55 kAU/L could predict omalizumab treatment response well, and the optimal sensitivity and specificity were 100.0% and 76.90%, respectively.

The Phadiatop™ test appears to outperform the measurement of TIgE levels and the classical hypothesis-driven approach to allergy diagnosis used to identify patients with severe allergic asthma, and may improve the clinical efficacy of IGE-targeted asthma therapy.