Analysis of blood eosinophil levels in relation to CT measured airway wall thickness and emphysema in end-stage COPD

Introduction: Measurement of blood eosinophil count in COPD is reported as a useful marker to identify patients with an increased risk for exacerbations. However, scarce information exists whether the degree of the blood eosinophil count has an impact on airway wall remodeling or emphysema. Therefore, the aim of this study was to investigate the effect of blood eosinophil levels in relation to CT measured airway wall thickness and emphysema. Methods: In a retrospective study design, we collected clinical data and chest CT scans from end-stage COPD patients and they were divided into either a high eosinophil blood count group (HE) or in a low eosinophil (LE) blood count group (defined as having eosinophils u003e2% of the total white blood cell count). CT measured airway wall thickness (Pi10) and emphysema score (Perc15) were analyzed in the total group and comparison of both groups was performed by using independent t-test or multiple linear regression analysis. Results: In total 109 patients (55 yrs±6.1) were analyzed and 44% of the patients showed increased eosinophil levels u003e2%. No differences in clinical characteristics, Pi10 or Perc15 were found between the HE and LE group. We stratified for the upper and lower 50% Perc15 level in the total patient group and this revealed a relation of blood eosinophil count to Pi10 in the upper 50% level (s value:0.56; SE 0.09; p=0.01). Conclusion: End-stage COPD patients with a lower grade of CT measured emphysema showed a relation between blood eosinophil count and airway wall thickness. No differences were found in clinical characteristics, Pi10 or Perc15 between patient groups with either blood eosinophil levels below or above 2%.