Breath Biopsy Assessment of Liver Disease Using an Exogenous Volatile Organic Compound—Toward Improved Detection of Liver Impairment

Abstract

INTRODUCTION: Liver cirrhosis and its complication — hepatocellular carcinoma (HCC) — have been associated with increased exhaled limonene. It is currently unclear whether this increase is more strongly associated with the presence of HCC or with the severity of liver dysfunction. METHODS: We compared the exhaled breath of 40 controls, 32 cirrhotic patients, and 12 cirrhotic patients with HCC using the Breath Biopsy platform. Breath samples were analyzed by thermal desorption–gas chromatography–mass spectrometry. Limonene levels were compared between the groups and correlated to bilirubin, albumin, prothrombin time international normalized ratio, and alanine aminotransferase. RESULTS: Breath limonene concentration was significantly elevated in subjects with cirrhosis-induced HCC (M: 82.1 ng/L, interquartile range [IQR]: 16.33–199.32 ng/L) and cirrhosis (M: 32.6 ng/L, IQR: 6.55–123.07 ng/L) compared with controls (M: 6.2 ng/L, IQR: 2.62–9.57 ng/L) ( P value = 0.0005 and 0.0001, respectively) with no significant difference between 2 diseased groups ( P value = 0.37). Levels of exhaled limonene correlated with serum bilirubin ( R 2 = 0.25, P value = 0.0016, r = 0.51), albumin ( R 2 = 0.58, P value = 5.3e-8, r = −0.76), and international normalized ratio ( R 2 = 0.29, P value = 0.0003, r = 0.51), but not with alanine aminotransferase ( R 2 = 0.01, P value = 0.36, r = 0.19). DISCUSSION: Exhaled limonene levels are primarily affected by the presence of cirrhosis through reduced liver functional capacity, as indicated by limonene correlation with blood metrics of impaired hepatic clearance and protein synthesis capacity, without further alterations observed in subjects with HCC. This suggests that exhaled limonene is a potential non-invasive marker of liver metabolic capacity (see Visual abstract, Supplementary Digital Content 1, http://links.lww.com/CTG/A388 ).

Assessment of Breathomics Testing Using High-Pressure Photon Ionization Time-of-Flight Mass Spectrometry to Detect Esophageal Cancer

“… 10 , 17 Cancer-derived metabolites can circulate to the lungs and diffuse into the alveoli via gaseous exchanges between blood and air. 18 Similar to the rapidly developing liquid biopsy techniques in cancer, 19 , 20 such as circulating cell-free DNA, circulating tumor cells, circulating micro-RNAs, or even exosomes in circulation, 21 metabolites in exhaled breath also contain valuable information about what happens within our bodies. Thus, testing breathomics holds great potential as an emerging breath biopsy.…”

Liver Impairment—The Potential Application of Volatile Organic Compounds in Hepatology

“…Ferrandino et al [ 58 ] followed up on the limonene-related hypothesis and by sampling cirrhotic patients, cirrhotic patients with HCC, and healthy controls, they focused on comparing the exhaled limonene levels of their groups to see how they relate with each other by performing a GS-MS analysis. They reported that limonene concentration was significantly higher in cirrhotic and cirrhotic patients with HCC when compared to healthy individuals.…”

Breath Biomarkers in Diagnostic Applications

“…These observations were explained by the inability of the compromised liver to breakdown this exogenous compound, compared with its efficient metabolism by CYP450 enzymes in the healthy cohort. Follow-up studies have further explored this phenomenon, with the inclusion of patient groups with hepatocellular carcinoma (HCC) and/or hepatic encephalography (HE) [ 257 , 258 ]. Similar observations were made, although no differences were found between liver cirrhosis with or without HCC, and the degree of HE severity could not be linked to limonene concentrations, although limonene accumulation was speculated to be itself a causative pathway for HE.…”