Table 2.

Comparison of airway samples for biomarker measurement

	Advantages	Disadvantages	Region sampled	Inflammatory biomarkers
Sputum	Well established Non-invasive	Requires immediate processing Difficult in young children	Most affected large airways	Cell counts Cytokines/proteins Metabolites
BAL	Can be used in all subjects	Higher risk (anesthesia) Expensive	Targeted smaller airways	Cell counts Cytokines/proteins Metabolites
EBC	Simple to collect Non-invasive	Very low and variable biomarker concentrations	Small airways (may under-sample plugged airways)	Cytokines/proteins Metabolites