Breath-Taking Perspectives and Preliminary Data toward Early Detection of Chronic Liver Diseases

Abstract

The gold standard method for chronic liver diseases diagnosis and staging remains liver biopsy, despite the spread of less invasive surrogate modalities based on imaging and blood biomarkers. Still, more than 50% of chronic liver disease cases are detected at later stages when patients exhibit episodes of liver decompensation. Breath analysis represents an attractive means for the development of non-invasive tests for several pathologies, including chronic liver diseases. In this perspective review, we summarize the main findings of studies that compared the breath of patients with chronic liver diseases against that of control subjects and found candidate biomarkers for a potential breath test. Interestingly, identified compounds with best classification performance are of exogenous origin and used as flavoring agents in food. Therefore, random dietary exposure of the general population to these compounds prevents the establishment of threshold levels for the identification of disease subjects. To overcome this limitation, we propose the exogenous volatile organic compounds (EVOCs) probe approach, where one or multiple of these flavoring agent(s) are administered at a standard dose and liver dysfunction associated with chronic liver diseases is evaluated as a washout of ingested compound(s). We report preliminary results in healthy subjects in support of the potential of the EVOC Probe approach.

Keywords: breath biopsy; chronic liver diseases; volatile organic compounds (VOC).

Figure 1

Limonene breath profile in healthy subjects before and after oral administration. (A) Breath limonene levels in 3 healthy subjects measured in triplicate after ≥10 h fasting and compared to ambient. (B) Breath limonene levels measured before and after oral administration at the indicated time points. Limonene ingestion induces a spike in breath after 30 min followed by a progressive reduction toward baseline levels. (C,D) Spectral features showing a limonene washout-like time course, which could be potential bioproducts (Pot. Biop.). A.U. = arbitrary units.

Figure 2

EVOC 2 breath profile. (A) Levels of EVOC 2 in ambient and breath from 3 healthy subjects fasted for ≥10 h. (B) EVOC 2 profile on breath before and after administration at the indicated time points. (C,D) Spectral features representing potential EVOC 2 bioproducts (Pot. Biop.). A.U. = arbitrary units.

Figure 3

EVOC 3 breath profile. (A) EVOC 3 breath levels in ambient and breath of fasted subjects. (B) EVOC 3 breath profile before and after administration. (C) Breath profile of a known EVOC 3 bioproducts (Pot. Biop.). A.U. = arbitrary units.