Blood eosinophil count thresholds and exacerbations in patients with chronic obstructive pulmonary disease

Abstract

<div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d408757e251">Background</h5> <p id="P2">Eosinophilic airway inflammation in COPD is associated with exacerbations and responsivity to steroids, suggesting potential shared mechanisms with eosinophilic asthma. However there is no consistent blood eosinophil level that has been used to define the increased exacerbation risk. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d408757e256">Objective</h5> <p id="P3">To investigate blood eosinophil levels associated with exacerbation risk in COPD</p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d408757e261">Methods</h5> <p id="P4">Blood eosinophil counts and exacerbation risk were analyzed in moderate-to-severe COPD subjects, using two independent studies of former and current smokers with longitudinal data. The COPDGene study was analyzed for discovery (n=1553) and the ECLIPSE study was analyzed for validation (n=1895). A subset of the ECLIPSE subjects were used to assess the stability of blood eosinophil counts over time. </p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d408757e266">Results</h5> <p id="P5">COPD exacerbation risk increased with higher eosinophil counts. An eosinophil threshold of ≥300 cells/μL showed adjusted incidence rate ratios (IRR) for exacerbations of 1.32 in COPDGene (95% confidence interval (CI) 1.10–1.63). The cutoff of ≥300 cells/μL was validated for prospective risk of exacerbation in ECLIPSE with adjusted IRR of 1.22 (95% CI 1.06–1.41) using 3 year follow up data. Stratified analysis confirmed that the increased exacerbation risk associated with an eosinophil count ≥300 cells/μL was driven by subjects with a history of frequent exacerbations in both COPDGene and ECLIPSE. </p> </div><div class="section"> <a class="named-anchor" id="S5"> <!-- named anchor --> </a> <h5 class="section-title" id="d408757e271">Conclusions</h5> <p id="P6">Patients with moderate to severe COPD and blood eosinophil count ≥ 300 cells/μL had an increased risk exacerbations in the COPDGene Study which was prospectively validated in the ECLIPSE Study. </p> </div>