Association of blood eosinophils with corticosteroid treatment failure stratified by smoking status among inpatients with AECOPD

Background Recent studies have suggested elevated blood eosinophils are independent predictors of response to corticosteroid therapy in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Smoking status has been shown to affect corticosteroid response. Whether the association between high blood eosinophils and corticosteroid treatment failure is modified by smoking has not been fully investigated so far. Objectives This study aimed to assess whether the association between high blood eosinophils and corticosteroid treatment failure is modified by smoking. Methods We included 3402 inpatients with AECOPD treated with corticosteroids at Beijing Chao-Yang Hospital from July 2013 to June 2021. Blood eosinophil counts were measured within 24 hours of admission. An eosinophil percentage ≥2% was considered as high eosinophilic. Smokers in this study were defined as current or former smokers. Treatment failure was defined as a worsening of AECOPD that led to adverse clinical outcomes or required further treatment or an extended hospital stay or hospitalisation following the exacerbation. Multivariate-adjusted logistic models were used to estimate the OR and 95% CI associated with treatment failure. Results There were 958 (28.2%) treatment failure events occurring. Patients with high eosinophils had a lower risk of treatment failure (OR 0.74, 95% CI 0.63 to 0.87) than patients with low eosinophils. Compared with never smoking and low eosinophilic group, the ORs for treatment failure were 0.70 (95% CI 0.52 to 0.96) for never smoking and high eosinophilic group, 0.82 (95% CI 0.64 to 1.05) for smoking and low eosinophilic group and 0.62 (95% CI 0.47 to 0.81) for smoking and high eosinophilic group. Furthermore, there was no significant interaction between eosinophils and smoking status in relation to treatment failure (p for interaction=0.73). Similar results were obtained from multiple secondary outcomes and subgroup analyses. Conclusion Elevated blood eosinophils are associated with a lower rate of corticosteroid treatment failure, regardless of smoking status. Smoking does not modify the association between blood eosinophil level and corticosteroid treatment failure among inpatients with AECOPD. Data are available on reasonable request. The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.