Inconsistencies in predictive models based on exhaled volatile organic compounds for distinguishing between benign pulmonary nodules and lung cancer: a systematic review

Table 4 Volatile organic compounds reported in at least two studies

Compound name	Frequency	Level of VOCs		Chemical Classes	CAS
Compound name	Frequency	LC> BPN	BPN> LC	Chemical Classes	CAS
2-hydroxyacetaldehyde	5	Yes		Aldehydes	141-46-8
4-hydroxyhexenal	2	Yes		Aldehydes	109710-37-4
Acrolein	2	Yes		Aldehydes	107-02-8
4-hydroxy-2-nonenal	2	Yes		Aldehydes	75899-68-2
Acetaldehyde	2	NR	NR	Aldehydes	141-46-8
4-hydroxyhexanal	2	Yes		Aldehydes	109710-36-3
Heptanal	2	NR	NR	Aldehydes	111-71-7
Hexanal	2	Yes		Aldehydes	66-25-1
Octanal	2	Yes		Aldehydes	124-13-0
2-butanone	4	Yes		Ketones	78-93-3
3-hydroxy-2-butanone	4	Yes		Ketones	513-86-0
Butyric acid	3	NR	NR	Acids	107-92-6
Acetic Acid	2	NR	NR	Acids	64-19-7
Propylcyclohexane	2	NR	NR	Alkanes	1678-92-8
Benzene	2	NR	NR	Aromatic compounds	71-43-2
Tetrachloroethylene	2	NR	NR	Haloalkanes	127-18-4

NR: Not Reported; CAS: Chemical abstracts service; LC: lung cancer; BPN: benign pulmonary nodules

ISSN: 1471-2466