Diagnosis of non-alcoholic fatty liver disease/non-alcoholic steatohepatitis: Non-invasive tests are enough.

Non-alcoholic fatty liver disease is a major cause of liver disease worldwide and the most common liver disorder in Western countries, affecting around 25% of the general population. Fibrosis is the major long-term histological prognostic criteria of this disease. Liver biopsy cannot be realistically performed in such a huge population and, moreover, has well-known limitations (invasiveness, rare but potentially life-threatening complications and sampling variability). Over the past decade, there has been a growing interest in alternative novel strategies for the non-invasive evaluation of fibrosis. These tests rely on two different but complementary approaches: either measuring the levels of serum biomarkers, or liver stiffness, using ultrasound-based elastography techniques. In non-alcoholic fatty liver disease patients, transient elastography, FIB-4 and the non-alcoholic fatty liver disease fibrosis score are the best validated tests, with summary area under the ROC curve values for diagnosing severe fibrosis-cirrhosis of 0.88, 0.84 and 0.84 respectively. They can also identify the subgroup of non-alcoholic fatty liver disease patients at high risk of developing liver-related complications and death. As a result, non-invasive tests are now widely used in routine clinical practice and included in national and international guidelines. The next step is the use of non-invasive tests as first-line tools for screening non-alcoholic fatty liver disease in the general population to identify patients who should be referred to specialized centres.