Table 2.

Alternative biomarkers for asthma diagnosis and management

Biomarker source	Advantages	Disadvantages
Exhaled breath condensate (EBC) – pH & proteins (Inflammatory markers; IL-6, IL-8, TNF-α, H2O2, leukotrienes, 8-isoprostane. Non-inflammatory markers; actin, cytokeratins, albumin)	Non-invasive, multiple biomarkers in sample therefore sub-phenotyping possible.	Collection techniques drastically affect proteins in sample, reproducibility a problem, salivary contamination, unproven clinical effectiveness.
Serum proteins (Leptin/adiponectin, eosinophillic cationic protein, chemokines, chitinases)	Less invasive, multiple biomarkers = sub-phenotyping, standardised collection and processing techniques.	Less sensitive and slower response to airway changes, unproven clinical effectiveness.
Urinary metabolites (>70) endpoints	Non-invasive, multiple biomarkers = sub-phenotyping, standarised collection and processing, good sensitivity and specificity.	Unproven clinical effectiveness (although preliminary data is positive), limited access to NMR equipment.