Background: Neutrophilic asthma and COPD are obstructive airway diseases common in older age and have a characteristic airway inflammation with neutrophilic bronchitis. The structural differences between neutrophilic asthma and COPD have not been investigated. The aim of this study was to examine the airway and parenchymal abnormalities using high resolution computed tomographic (HRCT) scanning in participants with neutrophilic asthma, COPD and smoking controls. Methods: Participants (neutrophilic asthma (n = 10), COPD (n = 17) and smoking controls (n = 8)) underwent clinical assessment and sputum induction. HRCT of the chest was performed and independently scored by a radiologist blinded to the subject group using a modified Bhalla scoring system. Results: Participants were of a similar age and those with COPD had a similar degree of airflow obstruction to those with neutrophilic asthma. The pattern of radiographic abnormalities differed between groups. Abnormal bronchial wall thickening was significantly more common in neutrophilic asthma, compared to COPD or smoking controls. Emphysema was greatest in the COPD group, and not recorded as a feature of neutrophilic asthma. FEV₁% predicted was negatively associated with bronchial wall thickening and consolidation while KCO% predicted was negatively associated with the total emphysema score. Bronchiectasis was minimal in all groups. Conclusion: The pattern of radiographic lung abnormality in neutrophilic asthma differs significantly from COPD, and resembles asthma. Neutrophilic asthma is a distinct inflammatory subtype of asthma with a different pathogenesis to COPD.
Respiratory Medicine Vol. 103, Issue 6, p. 881-887