Asthma patients will be diagnosed according to a clinical history of wheezing, cough, chest tightness or shortness of breath, as well as the presence of BHR (cumulative dose caus¬ing a 20% decrease in FEV1), based on the GINA guidelines. None of them had a history of COPD, or previous doctor-diagnosed ACO. All subjects had not used any oral or/and inhaled corticosteroid (ICS) in the previous 12 weeks. The included patients with asthma had initial diagnosis and were under uncontrolled stage.

COPD patients were diagnosed according to the GOLD criterion, which included a post-bronchodilator spirometry to confirm airflow obstruction (FEV1 to forced vital capacity ratio [FEV1/FVC] ,70%), in a clinical context (dyspnea, chronic cough or sputum production, and a history of expo¬sure to risk factors for the disease). They had received a COPD diagnosis at least 1 year before the study. None of them had a history of asthma. All subjects had not used any oral or/and ICS in the previous 4 weeks. The included COPD patients had exacerbations. The GOLD stage of COPD was defined according to the 2019 recommendations of GOLD.

ACO will be diagnosed by two steps: the first step is the identification of a history of chronic airway disease, i.e., chronic or recurrent cough, sputum production, wheezing, or repeated acute lower respiratory tract infections. In the second step, the features of asthma and those of COPD that best describe the patients

Sputum cytology refers to the examination of sputum (mucus) under a microscope to look for abnormal or cancerous cells. Sputum, or phlegm, is the fluid that is secreted by cells in the lower respiratory tract such as the bronchi and the trachea. It differs from saliva, in that it contains cells that line the respiratory passages.

A differential cell count will be obtained from 400 cells under 400× microscope to identify the severity and type of airway inflammation in all patients. Squamous cell count less than 10% in each sample will be deemed adequate for further analysis.