Non-interventional Study of COPD Patients With Asthma Overlap Syndrome in Viet Nam and Taiwan

Inclusion Criteria: * All patients with confirmed diagnosis of COPD {post-bronchodilator FEV1/FVC\<0.7 (FEV1 - forced expiratory volume at one second, FVC - forced vital capacity) based on the medical records} * Aged \>40 years old at time of diagnosis * Seen at out-patient clinic Exclusion Criteria: * Patients currently with acute exacerbation of COPD by GOLD definition (any worsening of a patient's respiratory symptoms that is beyond normal day-to-day variations and requires a change in medication) * Patients with respiratory diseases that can show similar symptoms to chronic airway diseases such as bronchiectasis, tuberculosis (TB)-destroyed lung parenchyma, endobronchial TB, and lung cancer, or those who have history of these diseases based on physician's judgment * Patients currently diagnosed with pneumonia and acute bronchitis * Patients currently randomized in other clinical studies