Clinical Characteristics of Asthma and COPD Overlap for Patients With Asthma and COPD in Hong Kong

Inclusion Criteria: Subjects must fulfil all of the following criteria: * All patients with confirmed diagnosis of COPD (post-bronchodilator FEV1/FVC\<0.7 based on the medical records) 1 or asthma (defined as those with a consistent history and prior documented evidence of variable airflow obstruction, with evidence of an increase in FEV1 greater than 12% or 400 mL following bronchodilator or bronchial hyperresponsiveness on bronchial provocation testing, when stable) 6 * Aged \>40 years old * Signed written informed consent to participate in the study 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) 1 or acute exacerbation of asthma by GINA guideline. 6 * 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