what is the differential diagnosis for COPD?
how do you exclude asthma?
no variable airflow obstruction, minimal response to bronchodilator/ steroids (however this may not be an exclusion of asthma so much as diagnosing an extra condition)
how do you exclude lung cancer?
no hypercalcaemia, no haemoptysis
how do you exclude left ventricular failure?
check on CXR
how do you exclude TB?
no haemoptysis