| Summary: | Background: Omalizumab may modulate airway remodeling in severe asthma. Using forced expiratory volume in 1 second (FEV 1 ) as a surrogate of airway remodeling, we aimed to investigate if an omalizumab add-on in severe allergic asthma may lead to a persistent reversal of airway obstruction and to evaluate the potential biomarkers of airway obstruction reversibility. Methods: Data were collected before (T0) and after omalizumab add-on for 1 year (T1, 32 patients), 2 years (T2, 26 patients) and 4 years (T4, 13 patients). All patients had baseline FEV 1 below 80 % predicted (60.5 ± 12.5 %). After omalizumab, 18 patients showed FEV 1 normalization (reversible airway obstruction; RAO+) already at T1 (88.7 ± 14.9 %, p < 0.0001) that persisted up to T4 (83.2 ± 7.9, p < 0.01), while 14 patients (RAO−) had FEV 1 persistently decreased, from T1 (65.2 ± 8.4%, p < 0.05) up to T4 (61.4 ± 6.2%, not significant). Both groups had significant improvement of symptoms and exacerbations after omalizumab at T1, which persisted up to T4. The comparison between pretreatment characteristics of the two groups showed that RAO+ patients, had higher values of circulating eosinophils, exhaled nitric oxide (F E NO), prevalence of rhinitis and nasal polyps, need of oral corticosteroids, shorter asthma duration, higher FEV 1 and response to albuterol test. The optimal cut-off points predicting FEV 1 normalization after omalizumab add-on were 30.5 ppb for F E NO and 305 cells/µl for eosinophils. Conclusions: This study suggests that omalizumab add-on contributes to the persistent reversal of airway obstruction in a consistent number of patients with severe allergic asthma, and this beneficial effect is predicted by elevated pretreatment F E NO and circulating eosinophils.
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