13C Methacetin Breath Test for Assessment of Microsomal Liver Function: Methodology and Clinical Application
BACKGROUND & OBJECTIVES The development and evaluation of non invasive tests to assess liver fibrosis have been an active field of research. The present study was carried out to evaluate the role of 13C-methacetin breath test 13C-MBT) as a non invasive tool for liver fibrosis staging in patients with chronic hepatitis C (CHC). METHODS 13C-Methacetin breath test was performed in 115 patients with CHC histologically proven and in 55 healthy controls. All patients and controls underwent routine liver function tests. The CHC patients underwent histological assesment of liver by percutaneous liver biopsy. The correlation between the 13C-methacetin breath test and liver biopsy was tested using Kendall's rank correlation coefficients. The overall validity was expressed as area under receiver operating characteristic curve (AUROC) with 95%CI. RESULTS Delta over baseline values (DOB) of CHC patients at 20 min were significantly reduced compared with control (16. 2 vs. 21. 06%, p <0.001). There were also significant differences between CHC patients and controls as regard the metabolization speed (dose/h at 20 min (17.80 vs 28.6, p <0.001) and metabolization capacity (cumulative recovery after 60 min (13.8 vs 20.4 p <0.001). The best 13C-MBT parameter correlated with fibrosis was DOB at 20 min (r = -0.596). The optimal cut-off for the diagnosis of advanced fibrosis (F ≥ 3) was 15.2 per cent, with AUROC = 0.902, 95%CI: (0.851-0.938), a sensitivity of 82 per cent and a specificity of 80 per cent. DOB at 20 min predicted even better cirrhosis: AUROC = 0.932 95 per cent CI = 0.901-0.953, a sensitivity of 96 per cent and a specificity of 92 per cent. INTERPRETATION & CONCLUSIONS Based on our findings the 13C-methacetin breath test appears to be a promising tool to identify CHC patients with advanced fibrosis and to replace liver biopsy. Further studies need to be done to assess its potential to be used in regular clinical practice.