[13C]methacetin breath test for evaluation of liver damage.

Methacetin undergoes rapid O-dealkylation by hepatic microsomal enzyme systems, and the resultant CO2 is present in the expired air. The rate of O-dealkylation of methacetin was assessed by the [13C]methacetin breath test in seven healthy volunteers and 30 patients with histologically proven chronic liver diseases. The 30-min recovery of orally administered [13C]methacetin as 13CO2 in the exhaled air was significantly reduced in patients with chronic aggressive hepatitis and in those with liver cirrhosis but not in patients with chronic persistent hepatitis or healthy controls. Patients with either advanced cirrhosis or hepatocellular carcinoma showed significantly lower values than those with well-compensated cirrhosis. The levels in two patients with late primary biliary cirrhosis were reduced. These results show that the severity of liver damage can be effectively evaluated by [13C]methacetin breath test. In addition, this test is simple, safe, and time efficient.