Breathomics Redefines Functional Liver Assessment : Clin Liver Dis | May 2026

Introduction

Chronic Liver Disease continues to rise globally, driven predominantly by Metabolic Dysfunction-Associated Steatotic Liver Disease and alcohol-associated liver disease. Accurate evaluation of fibrosis severity and hepatic functional reserve remains fundamental for prognostication, transplant assessment and therapeutic decision-making.

Problem Statement

Current diagnostic tools, including liver biopsy and serum-based fibrosis scores, primarily provide static structural information and incompletely capture real-time hepatic metabolic function. There remains an unmet need for dynamic, non-invasive methods capable of simultaneously assessing hepatocyte function, fibrosis burden and metabolic reserve.

Summary

This narrative review highlights the evolving role of breath-based diagnostics as a physiologically grounded approach for functional liver assessment. Unlike conventional fibrosis tools that estimate structural injury indirectly, breath testing evaluates active hepatic metabolic capacity in real time.

The review focuses primarily on isotope-based breath tests using 13C-labelled substrates. Following hepatic metabolism, these substrates generate measurable 13CO2 in exhaled breath, providing dynamic information regarding enzymatic activity, mitochondrial function, hepatic perfusion and viable hepatocyte mass.

Importantly, breath-test kinetics also reflect the functional consequences of fibrosis progression rather than merely quantifying scar burden. This creates a clinically relevant distinction between structural fibrosis assessment and true hepatic reserve evaluation.

The article further discusses volatile organic compound (VOC) analysis, an emerging “breathomics” strategy capable of identifying endogenous metabolic signatures associated with oxidative stress, inflammation and fibrogenesis. VOC profiling may eventually permit non-invasive molecular phenotyping of liver disease.

A major focus of the review is the development of the Liver Isoform Breath Assessment platform. LIBRA integrates multiple 13C-labelled substrates simultaneously to interrogate several hepatic metabolic pathways within a single assessment, thereby generating a composite measure of dynamic liver function.

Preliminary evidence suggests potential utility of LIBRA in fibrosis risk stratification, prediction of hepatic decompensation and transplant evaluation. By integrating multiple metabolic domains, LIBRA may provide a more comprehensive representation of hepatic reserve than conventional single-marker approaches.

The review also positions breath diagnostics within the broader movement toward precision hepatology. Functional metabolic phenotyping may eventually help distinguish biologically heterogeneous patient subgroups within MASLD and cirrhosis populations.

Clinically, breath testing offers several practical advantages. The technique is non-invasive, repeatable, radiation-free and potentially suitable for serial monitoring. Dynamic assessment may be particularly valuable in tracking disease progression, treatment response and peri-transplant physiology.

The review additionally emphasizes the conceptual shift from static fibrosis staging toward integrated structure-function assessment. Patients with similar fibrosis stages frequently demonstrate markedly different metabolic reserve and clinical trajectories, highlighting limitations of purely structural evaluation.

Importantly, the authors acknowledge several current limitations preventing routine clinical implementation. Standardization of testing protocols, validation across etiologies, establishment of diagnostic thresholds and demonstration of cost-effectiveness remain necessary before widespread adoption.

Technical variability, substrate selection, analytical platform harmonization and reproducibility across centers also require further refinement. Large prospective studies will be essential to determine whether breathomics meaningfully improves clinical outcomes beyond existing fibrosis algorithms.

Nevertheless, the review underscores the growing translational importance of non-invasive functional hepatology diagnostics. As MASLD prevalence increases globally, scalable tools capable of identifying patients at highest risk of decompensation and progression will become increasingly valuable.

Overall, this review positions breath-based diagnostics and multi-substrate platforms such as LIBRA as promising next-generation tools that integrate hepatic structure, metabolism and functional reserve, potentially reshaping future non-invasive assessment strategies in chronic liver disease.