Review article: the diagnosis of non-alcoholic fatty liver disease - availability and accuracy of non-invasive methods

Background Non-alcoholic fatty liver disease (NAFLD) encompasses a wide spectrum of clinical conditions, actually representing an emerging disease of great clinical interest. Currently, its diagnosis requires liver biopsy, an invasive procedure not free from potential complications. However, several non-invasive diagnostic strategies have been proposed as potential diagnostic alternatives, each with different sensitivities and accuracies. Aim To review non-invasive diagnostic parameters and tools for NAFLD diagnosis and to formulate a diagnostic and prognostic algorithm for a better classification of patients. Methods A literature search was carried out on MEDLINE, EMBASE, Web of Science and Scopus for articles and abstracts in English. The search terms used included NAFLD, non invasive method and NAFLD, transient elastography and liver fibrosis. The articles cited were selected based on their relevancy to the objective of the review. Results Ultrasonography still represents the first-line diagnostic tool for simple liver steatosis; its sensitivity could be enhanced by the complex biochemical score SteatoTest. Serum cytokeratin-18 is a promising and accurate non-invasive parameter (AUROCs: 0.83; 0.91) for the diagnosis of non-alcoholic steatohepatitis (NASH). The staging of liver fibrosis still represents the most important prognostic problem: the most accurate estimating methods are FibroMeter, FIB-4, NAFLD fibrosis score (AUROCs: 0.94; 0.86; 0.82) and transient elastography (AUROC: 0.841.00). Conclusions Different non-invasive parameters are available for the accurate diagnosis and prognostic stratification of non-alcoholic fatty liver disease which, if employed in a sequential algorithm, may lead to a reduced use of invasive methods, i.e. liver biopsy.