Clinical characteristics of asthma-chronic obstructive pulmonary disease overlap phenotypes

Introduction:
Asthma-chronic obstructive pulmonary disease overlap (ACO) patients are categorized as those with persistent airflow limitation and features of asthma and chronic obstructive pulmonary disease (COPD).

Aim:
This study aimed to identify ACO subgroups based on atopy, bronchodilator response (BDR), and eosinophil count.

Material and methods:
From 2021 to 2024, we conducted a retrospective study on patients with asthma and/or COPD who underwent BDR testing. An ACO diagnosis required persistent airflow limitation, a history of asthma before the age of 40 or significant BDR, and at least one minor criterion. Patients were grouped by atopy status, BDR presence, and eosinophil count. We compared demographic, laboratory, spirometry, and medication data across subgroups.

Results:
The study included 109 ACO patients with a mean age of 49.5 ±10.7 years. Atopic ACO patients showed a higher increase in FEV1 after inhalation of 400 µg of salbutamol or the equivalent (DFEV1BDR) and higher total IgE levels than non-atopic patients (200 ml vs. 100 ml, p = 0.034; 211 IU/ml vs. 60 IU/ml, p = 0.002). Eosinophil counts were higher in the BDR-positive group (360/µl vs. 195/µl, p = 0.047). High eosinophilic ACO patients also had elevated IgE levels (323 IU/ml vs. 80 IU/ml, p = 0.001). BDR-positive and eosinophilic groups demonstrated better spirometric results. Atopic ACO patients used more leukotriene receptor antagonists, while BDR-negative ACO patients used antimuscarinics.

Conclusions:
Higher DFEV₁BDR in atopic ACO indicates they may respond better to bronchodilators. Elevated eosinophil counts in BDR-positive patients support their classification and suggest less severe disease progression.