Table 1.

Summary of studies that compared the breath of subjects with chronic liver diseases, against controls. Compounds in bold and blue are of exogenous origin. Arrows indicate if a compound is elevated or reduced in the breath of disease subjects compared to controls. CLD = chronic liver diseases.

Author/Year	Study Design	Analytical Method	Discriminant VOCs	Calssification Performance
Friedman et al. (1994) [82]	24 CLD 24 Controls	GC-MS	Hydrogen-sulphide ↑ Limonene ↑	n/a
Sehnert et al. (2002) [83]	86 CLD 109 Controls	GC	Carbonyl sulphide ↑	n/a
Van den Velde et al. (2008) [84]	52 CLD 50 Controls	GC-MS	Acetone ↑ Dimethyl-sulphide ↑ 2-butanone ↑ 2-pentanone ↑ Indole ↓ Dimethyl-selenide ↓	100% sensitivity 70% specificity
Dadamio et al. (2012) [85]	35 CLD 49 Controls	GC-MS	Dimethyl-sulphide ↑ Acetone ↑ 2-butanone ↑ 2-pentanone ↑ Indole ↓ Phenol ↓ Dimethyl-selenide ↓ Isoprene ↑ Ethane ↑ Pentane ↑	83% sensitivity 100% specificity
Pijls et al. (2016) [86]	34 cirrhotic 87 non-cirrhotic 31 controls	GC-MS	Dimethyl-sulphide ↑ Terpene (limonene) ↑ 2-methyl-butanal ↓ Propanoic acid ↑ Octane ↑ Terpenoid ↑ 3-carene ↑ 1-hexadecanol ↓ C16H34 ↓	83% sensitivity 87% specificity
Morisco et al. (2013) [87]	12 CLD 14 Controls	PTR-MS	Heptadienol ↑ Methanol ↑ 2-butanone ↑ 3-pentone ↑ 2-octanone ↑ 2-nonanone ↑ Monoterpene ↑ P-cymene ↑	83% sensitivity 86% specificity
Fernandez Del Rio et al. (2015) [88]	31 CLD 30 Controls	PTR-MS	Methanol ↑ 2-butanone ↑ Carbon-sulphide ↑ 2-pentanone ↑ Limonene ↑	97% sensitivity 70% specificity
Sinha et al. (2020) [89]	15 chirrosis NAFLD 14 non-cirrhosis NAFLD 14 Controls	GC-MS	Styrene Acetone Isoprene DMS D-limonene Acetophenone Terpinene	Cirrhotic vs. Control: AUCs = 0.98 Cirrhotic vs. Non-cirrhotic: AUC = 0.91 Non-Cirrhotic vs. Control: AUC = 0.84
Ferrandino et al. [90]	44 cirrhosis 42 controls	GC-MS	Limonene	AUC = 0.78