Tests for diagnosing and monitoring non-alcoholic fatty liver disease in adults

Non-alcoholic fatty liver disease (NAFLD) is a metabolic liver disease that encompasses a spectrum of progressive pathological conditions, ranging from non-alcoholic fatty liver (NAFL) to steatohepatitis (NASH), fibrosis, and cirrhosis. When hepatic steatosis occurs in the absence of excessive alcohol consumption and other recognised causes of liver fat, and with cardiometabolic risk factors, it is likely that the diagnosis is NAFLD as NAFLD is principally a diagnosis of exclusion. NAFLD is the commonest liver disease in high income countries, and is estimated to affect at least 25%-30% of adults in the general population and up to 70%-90% of persons with obesity or type 2 diabetes.1NAFLD is associated not only with liver related morbidity and mortality, but also with an increased risk of developing cardiovascular disease and type 2 diabetes.2 3 Liver biopsy remains the reference method for diagnosing NAFLD, as it provides the most accurate assessment of disease grade and stage.4 5 However, undertaking a liver biopsy is costly, risky, and potentially painful. Moreover, interpretation of NAFLD severity can be compromised by sampling errors in what can be a patchy disease.6 7 In this article, we discuss the diagnosis of NAFLD, testing for liver fibrosis in those with NAFLD, and monitoring of those most likely to develop advanced liver disease. We examine the evidence and guidelines from Europe, the United States, and the UK’s National Institute for Health and Care Excellence (NICE)8-10 for and against the use of specific diagnostic tests. Our approach to the use of liver ultrasound in establishing a diagnosis of hepatic steatosis differs from the recent NICE guidelines,10 but complements British Society of Gastroenterology guidelines.11 Treatment options are beyond the scope of this article.