13C‐methacetin breath test as liver function test in patients with chronic hepatitis C virus infection

SummaryBackground : The 13C‐methacetin breath test enables the quantitative evaluation of the cytochrome P450‐dependent liver function.Aim : To find out whether this breath test is sensitive in noncirrhotic patients also with chronic hepatitis C in early stages of fibrosis.Methods : Sixty‐one healthy controls and 81 patients with chronic hepatitis C underwent a 13C‐methacetin breath test. In all patients, a liver biopsy was performed. The liver histology was classified according to the histology activity index–Knodell score.Results : Delta over baseline values of the patients at 15 min significantly differed from controls (19.2 ± 9.2‰ vs. 24.1 ± 5.7‰; P < 0.003). The cumulative recovery after 30 min in patients was 11.4 ± 4.8% and in healthy controls 13.8 ± 2.8% (P < 0.002). However, patients with early fibrosis (histology activity index IVB) did not differ in delta over baseline values of the patients at 15 min (23.2 ± 7.9‰ vs. 22.6 ± 7.2‰; P = 0.61) or cumulative recovery (13.6 ± 3.7% vs. 13.2 ± 3.8%; P = 0.45) from patients with more advanced fibrosis (histology activity index IVC). Patients with clinically nonsymptomatic cirrhosis (histology activity index IVD; Child A) metabolized 13C‐methacetin to a significantly lesser extent (delta over baseline values of the patients at 15 min: 8.3 ± 4.9‰; P < 0.005 and cumulative recovery after 30 min: 5.6 ± 3.2%; P < 0.003). The 13C‐methacetin breath test identified cirrhotic patients with 95.0% sensitivity and 96.7% specificity.Conclusion : The non‐invasive 13C‐methacetin breath test reliably distinguishes between early cirrhotic (Child A) and noncirrhotic patients, but fails to detect early stages of fibrosis in patients with chronic hepatitis C.