Patients with both chronic obstructive pulmonary disease (COPD) and chronic bacterial infection who had <100 circulating eosinophils/µL were at high risk of developing pneumonia, according to study results published in the American Journal of Respiratory and Critical Care Medicine.
Researchers conducted a post hoc long-term observational study to examine blood work and airway microbiology information from patients with concurrent COPD and chronic bacterial infection with the intent of determining risk factors for pneumonia development. The levels of circulating eosinophils were compared between groups of patients who either did or did not develop pneumonia during a period of 84 months.
Of the 227 patients recruited, 26 were excluded due to a lack of valid sputum samples for microbiologic analysis. Among the remaining 201 patients (90.5% men), the mean age was 70.3±9 years, and the mean forced expiratory volume in 1 second percent predicted was 49%. Older age, more severe airflow limitation, presence of bronchiectasis, and having <100 eosinophils/μL were all significantly related to both a single potentially pathogenic microorganism isolation and the presence of chronic bacterial infection.
Furthermore, older age, severity of airflow limitation, single isolation of a potentially pathogenic microorganism, presence of chronic bacterial infection, <100 eosinophils/μL, bronchiectasis, and treatment with inhaled corticosteroids were all significantly associated with a higher risk for pneumonia. Of these risk factors, chronic bacterial infection had the highest hazard ratio (2.976; 95% CI, 1.915-4.845).
The researchers wrote that their results showed “…for the first time that the presence of [chronic bacterial infection] and reduced eosinophil levels interact to increase the risk [for] pneumonia in [patients with COPD], since patients with both factors had a 3.1 [times] higher risk of suffering pneumonia than those without any of these 2 conditions.” They added that this risk could be further increased by the use of inhaled corticosteroids.
Martinez-Garcia MA, Faner R, Oscullo G, et al. Inhaled steroids, circulating eosinophils, chronic airway infection and pneumonia risk in chronic obstructive pulmonary disease: a network analysis [published online January 10, 2020]. Am J Respir Crit Care Med. doi:10.1164/rccm.201908-1550OC