Eosinophilia is common in COPD exacerbation and associated with non-infectious aetiology.

Abstract

Introduction/Aim: Serum eosinophils are an emerging biomarker and therapeutic target in airways disease. Eosinophilia may predict exacerbations and corticosteroid response, and is a proposed 'COPD exacerbation phenotype'. It is also a target for emerging monoclonal antibody therapies. Conversely, eosinopenia predicts mortality in COPD exacerbations (DECAF score). We examined the profile of serum eosinophils in hospitalized COPD exacerbations. Method(s): A total of 1781 potential exacerbations between September 2012 and October 2013 were identified via Monash Health database. Casenote analysis identified 565 COPD exacerbations. Pathology results were retrospectively examined in all patients with eosinophil counts (n = 565 admissions; 412 patients). Elevated eosinophil counts were classified according to both absolute (>0.5 109 L) and relative criteria (>2% total WCC). Eosinopenia was defined as <0.05 109 L. Exacerbations were subsequently classified as 'infectious' (viral PCR positive OR CRP > 20 mg/dL in first 48 h) or 'non-infectious' (viral PCR negative AND CRP < 20 mg/dL in first 48 h). Result(s): Use of the >2% relative threshold identified 35% of all exacerbations as eosinophilic, compared to 13%using the absolute threshold. Eosinophils peaked on day 1 in 71% of admissions. Eosinophilia (>2%) was significantly more prevalent in 'non-infectious' (36%) versus 'infectious' (16%) exacerbations (P < 0.001). Eosinopenia was observed in 40% of admissions overall and present in 64% of 'infectious' exacerbations versus 52% of 'non-infectious' exacerbations. Conclusion(s): Eosinophilia is common in COPD exacerbations although prevalence rates vary according to threshold criteria. It appears to be more prevalent in non-infectious exacerbations. Eosinopenia is also highly prevalent and may reflect an antimicrobial response or pre-treatment with corticosteroids.