Breath: An often overlooked medium in biomarker discovery

Exhaled breath offers an alternative medium for detecting certain types of biomarkers. Further, in some respects, analyzing breath has distinct advantages over blood analysis. Before contemplating breath gas analysis, however, this chapter first briefly considers the lungs. Volatile organic compounds (VOCs) in exhaled breath can generally be placed into two categories exogenous VOCs and endogenous VOCs. Both types of VOCs are of relevance in breath biomarker discovery. Precise and efficient breath sampling is a prerequisite for accurate breath analysis, but the exact method of sampling will inherently depend on the analytical system used. Analytical tools for breath analysis run the gamut from simple point-of-care systems to extremely complex laboratory instruments. Confounders can arise from a number of sources, but are predominantly reflective of suboptimum breath sampling or extraneous factors affecting the breath composition. These are discussed in more detail in this chapter.