Background: The diagnosis of NASH needs a liver biopsy, an invasive procedure that is not frequently accepted by patients. The aim of our study was to evaluate the efficacy of the ¹³C-Octanoate breath test (OBT) as a non-invasive surrogate marker to differentiate patients with NASH from patients with simple steatosis (NAFL). Methods: We performed a prospective study on patients with histologically established non-alcoholic steatohepatitis and no other hepatic disease. Each patient underwent a testing protocol, which included a clinical exam, laboratory blood tests, standard abdominal ultrasound, and a ¹³C-Octanoate breath test. Results: The study group included: 82 patients with steatohepatitis, 64 patients with simple steatosis, and 21 healthy volunteers. The univariate and bivariate analysis identified that significant values were the percent dose recovery (PDR) at 15 min—r = 0.65 (AUROC = 0.902) and cumulative percent dose recovery (cPDR) at 120 min—r = 0.69 (AUROC = 0.899). Discussion: Our study showed that ¹³C-OBT had good efficacy for identifying patients with NASH from those with NAFL (steatosis alone) but not those with NAFL from healthy subjects. Considering all these pathogenic steps in NASH we considered that OBT could have the clinical utility to identify patients at risk for NASH, especially “fast progressors”.

Background: While non-alcoholic fatty liver disease (NAFLD) is a wide-spread liver disease, only some patients progress towards steatohepatitis and cirrhosis. Aim: We comparatively analyzed the methacetin breath test (MBT) for the microsomal function of the liver and the octanoate breath test (OBT) for mitochondrial activity, in detecting patients with steatohepatitis and estimating fibrosis. Methods: 81 patients with histologically proven NAFLD (SAF score) were evaluated. The parameters used for both breath tests were the dose/h and the cumulative dose recovery at multiple timepoints. The statistical association between histological diagnosis and breath test results used Independent Samples t Test. The accuracy for diagnosis was evaluated using area under the receiver operator characteristic (AUROC) and the sensitivity and specificity were assessed using the Youden J method. Results: Both MBT and OBT were able to differentiate patients with simple steatosis from NASH and to stratify patients with significant fibrosis and cirrhosis (p-values < 0.001 for most analyzed timepoints). The best parameter for NASH diagnosis was OBT dose at 30 min. In the case of significant fibrosis, the most accurate test was MBT cumulative dose at 30 min. Conclusions: Both MBR and OBT tests are potentially useful tools in assessing patients with NAFLD.