Diagnosis and assessment of disease severity in patients with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) includes simple steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, and eventually cirrhosis and hepatocellular carcinoma (HCC). The diagnosis of NAFLD is based on the detection of excess fat disposition in the liver, which is the first step to trigger further evaluation of NAFLD, including necroinflammation and fibrosis. In this review, we discuss non-invasive biomarkers and imaging tools that are currently and potentially available for different features (steatosis, necroinflammation and fibrosis) and disease severity assessment of NAFLD. In the past 2 decades, advances in non-invasive tests of fibrosis have transformed the management of NAFLD. Blood and imaging biomarkers have already been evaluated in multiple studies for the diagnosis of fibrosis and cirrhosis. Among the various histological features of NAFLD, the degree of fibrosis has the strongest correlation with liver-related morbidity and mortality. Non-invasive tests of fibrosis have been shown to predict liver-related outcomes, both in the general population and among patients with NAFLD. What is lacking, however, is good data to support the use of non-invasive tests as monitoring and response biomarkers. With the conclusion of several large phase 3 studies in the next few years, the availability of paired liver biopsy, non-invasive test and clinical outcome data will likely advance the field and shed light on new biomarkers and the way to use various non-invasive tests in a longitudinal manner.