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J Breath Res

Title:		Clinical breath analysis: discriminating between human endogenous compounds and exogenous (environmental) chemical confounders
Author(s):		Pleil JD; Stiegel MA; Risby TH;
Address:		"Human Exposure and Atmospheric Sciences Division, NERL/ORD, US Environmental Protection Agency, Research Triangle Park, NC, USA. pleil.joachim@epa.gov"
Journal Title:		J Breath Res
Year:		2013
Volume:		20130227
Issue:		1
Page Number:		17107 -
DOI:		10.1088/1752-7155/7/1/017107
ISSN/ISBN:		1752-7163 (Electronic) 1752-7155 (Linking)
Abstract:		"Volatile organic compounds (VOCs) in exhaled breath originate from current or previous environmental exposures (exogenous compounds) and internal metabolic (anabolic and catabolic) production (endogenous compounds). The origins of certain VOCs in breath presumed to be endogenous have been proposed to be useful as preclinical biomarkers of various undiagnosed diseases including lung cancer, breast cancer, and cardio-pulmonary disease. The usual approach is to develop difference algorithms comparing VOC profiles from nominally healthy controls to cohorts of patients presenting with a documented disease, and then to apply the resulting rules to breath profiles of subjects with unknown disease status. This approach to diagnosis has a progression of sophistication; at the most rudimentary level, all measurable VOCs are included in the model. The next level corrects exhaled VOC concentrations for current inspired air concentrations. At the highest level, VOCs exhibiting discriminatory value also require a plausible biochemical pathway for their production before inclusion. Although these approaches have all shown some level of success, there is concern that pattern recognition is prone to error from environmental contamination and between-subject variance. In this paper, we explore the underlying assumptions for the interpretation and assignment of endogenous compounds with probative value for assessing changes. Specifically, we investigate the influence of previous exposures, elimination mechanisms and partitioning of exogenous compounds as confounders of true endogenous compounds. We provide specific examples based on a simple classical pharmacokinetic approach to identify potential misinterpretations of breath data and propose some remedies"
Keywords:		"*Breath Tests Environmental Exposure Exhalation Humans *Models, Biological *Models, Statistical Volatile Organic Compounds/*metabolism/*pharmacokinetics;"
Notes:		"MedlinePleil, Joachim D Stiegel, Matthew A Risby, Terence H eng England 2013/03/01 J Breath Res. 2013 Mar; 7(1):017107. doi: 10.1088/1752-7155/7/1/017107. Epub 2013 Feb 27"