The prevalence of asthma-COPD overlap (ACO) among COPD patients and the role of prostaglandin D2 (PGD2) in differential diagnosis

Purpose: Asthma-COPD overlap (ACO) is a disease similar to Chronic Obstructive Pulmonary Disease (COPD) with some features of asthma. In the Global Initiative for Asthma (GINA) and Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines, it is defined as “asthma and COPD symptoms accompanying each other at similar rates in cases with persistent airflow limitation (postbronchodilator FEV1/FVC70%)”. We aimed to investigate the frequency of patients with ACO according to GINA and GOLD criteria among those we followed with the diagnosis of COPD and to compare their clinical features and laboratory findings. We evaluated prostaglandin D2 (PGD2) levels in these patients and investigated whether it could be used as a parameter in the differential diagnosis of ACO.Materials and methods: Patients with COPD who applied to the chest diseases outpatient clinics of 3 hospitals in Denizli were examined between October 2021 and May 2022. Patients aged 40 years and older, who were followed up and treated with COPD by a pulmonologist for at least one year and who gave consent were included in the study. The presence of reversibility was investigated by pulmonary function test (PFT) in all patients. If the postbronchodilator FEV1/FVC was 70% in the patients included in the study and the reversibility was positive, it was considered as ACO. Patients divided into two groups as COPD and ACO were compared in terms of clinical, laboratory, PFT and hospital admissions.Results: A total of 166 COPD patients were included in the study. 158 of the patients were male and 8 were female, and their mean age was 61.48 (40-84). 30 (18.07%) patients included in the study with the diagnosis of COPD were diagnosed with ACO. While the mean blood eosinophil percentage in ACO patients was higher than in COPD patients, the mean blood neutrophil counts and percentages were lower than in COPD patients (p=0.02, p=0.02, and p=0.03, respectively). Total IgE level of the COPD group was higher than the ACO group (p=0.006).Conclusion: In our study, PGD2 was ineffective in differentiating ACO patients from COPD patients; mean blood eosinophil percentages and mean blood neutrophil percentages were useful but insufficient.