Chest X-ray and/or CT scans can support a COPD diagnosis or exclude other diseases. A full blood count should be given to check for anaemia or polycythaemia (excess red blood cells).[4]

COPD symptoms typically develop progressively, with a history tobacco use or other risk factors. Asthma is distinguishable by the airway obstruction being variable, with symptoms ranging widely from day to day.[7]

Bronchiectasis arises when there is persistent dilation of the bronchi due to irreversible damage to the elastic and muscular components of the bronchial wall. It would normally be suggested by large volumes of purulent sputum, often due to bacterial infection, and chest X-ray would normally show dilated bronchi. However, bronchiectasis can be caused by injury or inflammation not due to infection.[7,14]

TB can occur at any age, and would show lung infiltration on X-ray, confirmed by microbiological testing.[7]

Additional investigations when exploring the possibility of COPD can include electrocardiogram (ECGs), echocardiograms and testing blood levels of natriuretic peptides (hormones that regulate the cardiovascular system) to indicate cardiac disease or pulmonary hypertension rather than COPD.[4]

Congestive heart failure may be detected with an X-ray showing heart dilation and pulmonary oedema. Lung function tests would also indicate a reduced volume rather than airflow obstruction.[7]