Exhaled breath testing - A tool for the clinician and researcher.

Exhaled breath is a robust matrix of biomarkers divided between three fractions - gaseous breath, volatile breath, and breath condensate. Breath is collected non-invasively through bags (for gaseous breath), cold condensation chambers (breath condensate), and adsorbent traps (volatile breath). Due to the incredibly dilute nature of breath matrices, breath biomarker analysis requires precise analytical techniques, highly sensitive technology and often challenges the limit of detection of even the most advanced assays. Interest and advances in breath collection, analysis, and use have increased in recent years largely due to advances in analytical technology. Approved and validated breath tests are available as tools for researchers and clinicians. Novel development is ongoing. This article reviews the current applications for exhaled breath biomarkers.