Does atopy matter in difficult asthma? Results from WATCH

Background: Atopic sensitization represents one of the most recognisable characteristics associated with asthma but its role within the difficult adult asthma cohort is less understood. Aim: To evaluate the prevalence of atopy within patients with difficult asthma in the Wessex AsThma CoHort of difficult asthma (WATCH). Methods: Skin prick data is available from 314 patients currently enrolled into this prospective observational cohort study. Atopy was defined as a positive skin prick test to a panel of common aeroallergens (mould, pollen, dust mites, feathers and pet dander). Results: 68.2% patients were atopic. 59.8% of patients were sensitised to both seasonal and perennial allergens, 7.5% seasonal alone and 32.7% perennial alone. The most commonly positive tests were to D Pteronyssinus (47.3%), Grass Pollen (42.6%) and Cat (40.5%). 21.4% of our patients have had Omaluzimab (Xolair) treatment. Compared to non-atopic patients, atopic patients had a younger age of onset (median 13 vs 28, p<0.005) but we found no differences in BMI or gender. In terms of co-morbidities, eczema was more prevalent in atopic patients (26.1% vs 13.0%, p<0.05) but otherwise there no statistically significant differences. Total IgE was greater in atopic patients (median 120.0 vs 34.9, p<0.005) but we found no differences in serum eosinophils, spirometry, FeNO, ACQ6 or HADS. Similarly, we found no differences in healthcare utilisation: days lost from work, OCS courses or hospitalisations in the past 12 months. Conclusion: We find atopic sensitisation highly prevalent in difficult asthma and, though associated with early onset disease, stratification by atopy alone does not appear useful in differentiating disease severity.