To explore the relationship between blood eosinophil counts, asthma exacerbations and patient asthma control using a large primary care based research database

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.

Inclusion Criteria:

• Patient aged 12-80 at date of last eosinophil count
• Asthma diagnosis at any time
• Blood Eosinophil reading in patient record (numeric count expressed in µl) at least one year prior to last data extraction
• Two years of continuous data

Exclusion Criteria:

• Any other chronic respiratory diseases
• Eosinophil counts >5000/µl (outliers)

A retrospective database analysis of asthma patients with a valid eosinophil count (where valid: numeric value expressed as /µl at least one year prior to last data extraction) with at least one year of data of prior to the date of eosinophil count (baseline period) and one year of data post recorded eosinophil count (outcome period).