Assessment of liver function in acute or chronic liver disease by the methacetin breath test: a tool for decision making in clinical hepatology

Patients suffering from acute or chronic liver disease require on-going assessment of disease progression in terms of the degree of hepatic fibrosis and overall liver impairment. This assessment is pivotal for determining the prognosis and for making decisions about medical treatment and liver transplantation. Currently available methods are either invasive, lack diagnostic accuracy or are limited by technical difficulties such as obesity or biochemical confounders. The metabolic breath test relies on the measurement of tagged metabolites of an organ-specific substrate in the exhaled breath. C-13-methacetin is metabolized uniquely by the liver, and (CO2)-C-13 is measured continuously in the exhaled breath. Measuring this liver-specific substrate using molecular correlation spectroscopy provides a rapid, point-of-care, non-invasive method to assess liver function. The use of the C-13-methacetin breath test (MBT) may provide a powerful tool for clinical hepatologists in decision making at the bedside. This paper reviews recent findings regarding the ability of the point-of-care C-13-MBT to assess fibrosis, cirrhosis and hepatic functional reserve in patients with acute and chronic liver disease.