Evaluation of the 13C-methacetin breath test for quantitative liver function testing

Noninvasive 13C-breath tests are used for the assessment of hepatocellular dysfunction. 13C-methacetin is metabolized in the liver by O-demethylation to 13CO2 and acetaminophen. The aim of the study was to evaluate the 13C-methacetin breath test in comparison to the Child-Pugh score and other quantitative liver function tests (MEGX-test and indocyanin green-clearance). 2 mg/kg 13C-methacetin were orally given to 31 patients with histologically proven liver cirrhosis of different etiology and severity (nine Child A, 13 Child B, nine Child C), ten patients with chronic viral hepatitis and ten healthy volunteers. The increase of exhaled 13CO2 was expressed as delta over baseline (DOB; delta /1000). Different DOB-values were compared as parameters for assessing hepatocellular dysfunction. All breath test parameters analyzed provided an excellent discrimination between cirrhotic and noncirrhotic individuals. The DOB-value at 20 min showed a superior correlation with the Child-Pugh score (r = 0.67) than did MEGX-test or indocyanine green clearance results (r = 0.39 and r = 0.43, respectively). With a cut-off value of < or = 25 delta /1000 at 20 min, sensitivity and specificity to discriminate between cirrhotic and noncirrhotic individuals was 93.5% and 95%, respectively. The 13C-methacetin breath test is a safe and precise quantitative liver function test. Using one single breath sample 20 min after substrate administration, the test discriminates well between cirrhotic and noncirrhotic patients. Its prognostic value remains to be established.