Validation and further insight into the International Severe Asthma Registry (ISAR) eosinophil gradient algorithm in the Wessex AsThma CoHort of difficult asthma (WATCH) using historical blood eosinophil counts and induced sputum. Issue 6 (21st February 2022) - Barber, Clair; Azim, Adnan; Newell, Colin; Kyyaly, Aref; Rupani, Hitasha; Haitchi, Hans Michael; Howarth, Peter; Kurukulaaratchy, Ramesh