Sputum eosinophil levels have been shown to predict asthma exacerbation and inhaled corticosteroid (ICS) responsivenesss. Managing asthma based on sputum eosinophils leads to fewer exacerbations than management adhering to Global Initiative for Asthma (GINA) guidelines. However the use of sputum to measure eosinophil levels is expensive and impractical within a clinical setting. This study explores the use of blood-eosinophil levels as a clinical predictor for exacerbations and asthma control within a UK primary care dataset.