Table 1.

Advantages and disadvantages of currently used asthma biomarkers

Biomarker	Advantage	Disadvantage
Pulmonary function tests (PFTs) (FEV1, AHR)	Non-invasive, well validated, sensitive – ie, will detect all asthmatics, reproducible, PFTs will change rapidly with treatment.	Unable to identify sub-phenotypes of asthmatics, PFTs do not reflect pathology, PFTs cannot predict treatment response.
Tissue biopsy	Definitive measure of airway inflammation.	Highly invasive, disconnect between cell counts and symptoms, time consuming, requires high level of expertise.
Induced sputum (differential inflammatory cell counts)	Less invasive than tissue biopsy, reliable indicator of airway inflammation.	Very uncomfortable process, limited to children >8 yrs, requires expertise, reproducibility problems.
Exhaled nitric oxide (FeNO)	Non-invasive, simple measurement methods, indicates treatment (steroid) response.	Proven only for a sub-set of asthmatics, expensive equipment, a single biomarker reflects a single pathology.