Abstract
Targeted treatment strategies for asthma require a precise diagnosis of phenotypes. 308 adult patients (age mean±SD: 50.3±13.5yrs) with severe asthma from the German Severe Asthma Registry (www.german-asthma-net.de) were evaluated based on history of allergy symptoms, results of skin prick tests, total/specific IgE, and blood cell differentials. 121 patients (39%) showed typical signs of allergic asthma including allergic symptoms and a positive skin prick test and/or specific IgE with no elevated blood eosinophils (median total IgE: 222 (range 4-4023) IU/ml, eosinophils: 128 (0-295)/µl, FeNO: 23 (7-300) ppb). 53 (43.8%) of these patients were treated with omalizumab. 50 patients (16%) had asthma with elevated blood eosinophils (>300/µl) with no clinical or serological signs of allergy (median total IgE: 156 (18-5000) IU/ml), eosinophils: 586 (300-8500)/µl, FeNO: 51 (16-258) ppb. 75 patients (24%) had signs of allergy and elevated blood eosinophils (median total IgE: 310 (range 25-2345) IU/ml), eosinophils: 512 (300-11000)/µl, FeNO: 44 (10-228) ppb).Patients with features of allergic or eosinophilic disease or both differed significantly in age at diagnosis (21.9±17.6 yrs vs 38.7±15.4 yrs vs 28.6±15.8 yrs, p<0.001) and BMI (28.4±6.2 vs 25.9±6.5 vs 26.9±5.6, p= 0.031). There was also a difference in FEV1 (65.3±20.1% vs 58.7±21.7% vs 62.6±20.3%, p= 0.181). Daily doses of inhaled and oral steroids and exacerbation frequencies were similar.The results confirm the presence of clinically relevant phenotypes among severe asthma patients. As a first step, simple diagnostic criteria (e.g. allergy tests, serum IgE, blood eosinophils) are sufficient to identify potential patients for targeted therapies.