Predicting inhaled steroid responsiveness using blood eosinophil counts: personalising long-term management of COPD in primary care
Ashdown HF.
Background Management of chronic obstructive pulmonary disease (COPD), including initiation of inhaled corticosteroids (ICS), has thus far generally been based on a ‘one-size-fits-all’ approach. However, benefits of ICS are unclear, and they may harm some patients. Blood eosinophils have been identified as a readily available biomarker to guide decisions about ICS treatment in COPD, but they have not been studied in an ICS-naïve, primary care population. A device for estimating blood eosinophil counts at the point of care is now available. This doctoral project aimed to characterise blood eosinophils and ICS responsiveness in people with COPD in primary care, as well as assess agreement between near-patient vs. laboratory testing for blood eosinophils. Methods This project comprises two major studies, each with several constituent parts. First, a study of 30,378 routinely-collected primary care records were used for descriptive and hypothesis-testing components. Second, a prospective cohort study recruited 96 participants to obtain laboratory and near-patient blood eosinophil data at multiple visits over a six-month period. Results Approximately half of patients fell into a ‘medium’ category of eosinophils in the range 0.15 to 0.34 x10*9/L. Repeatability of eosinophil counts was either ‘good’ or ‘excellent’ in the two cohorts. There was a lower risk of acute exacerbations in patients with higher eosinophil counts who were prescribed an ICS, with a clear ‘dose-response’ by eosinophil count. There was no clinically important difference between near-patient and laboratory eosinophil values. Conclusions Patients with higher blood eosinophils are more likely to benefit from ICS. Blood eosinophil counts are generally repeatable and are applicable for guiding ICS treatment decisions in primary care. Blood eosinophil categories in combination with other clinical features such as acute exacerbation frequency could provide a more personalised approach to pharmacological management of COPD. Near-patient eosinophil count testing could support rapid decisions about ICS treatment in primary care.