Box 1.

Differential diagnoses in severe asthma*.

COPD Bronchiectasis Sarcoidosis Bronchiolitis obliterans Cystic Fibrosis Hypersensitivity pneumonitis Hypereosinophilic lung diseases Tracheobronchomalacia Pulmonary embolism Coronary Heart Failure Endobronchial tumor/foreign body

*Differential diagnostic conditions which commonly co-exist with asthma are listed under co-morbidities in Table 2.