Diagnosis of non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) increases risk of mortality from liver and cardiovascular disease (CVD) and is the major cause of hepatocellular carcinoma (HCC), which may develop without cirrhosis. NAFLD predicts type 2 diabetes, even independently of obesity. Globally, the prevalence of NAFLD averages 25% and is as common as the metabolic syndrome. The majority of patients with type 2 diabetes have NAFLD. The challenge for the diabetologist is to identify patients at risk of advanced liver disease and HCC. At a minimum, liver function tests (LFTs), despite being neither specific nor sensitive, should be performed in all patients with the metabolic syndrome or type 2 diabetes. Increases in LFTs, for which the updated reference values are lower (serum ALT ≈30 U/l in men and ≈20 U/l in women) than those hitherto used in many laboratories, should prompt assessment of fibrosis biomarkers and referral of individuals at risk to a NAFLD/hepatology clinic. Preferably, evaluation of NAFLD should be based on measurement of steatosis biomarkers or ultrasound if easily available. A large number of individuals carry the patatin-like phospholipase domain containing 3 (PNPLA3) I148M variant (30-50%) or the transmembrane 6 superfamily member 2 (TM6SF2) E167K variant (11-15%). These variants increase the risk of advanced liver disease and HCC but not of diabetes or CVD. Genotyping of selected patients for these variants is recommended. Many patients have 'double trouble', i.e. carry both a genetic risk factor and have the metabolic syndrome. Excess use of alcohol could be a cause of 'triple trouble', but such patients would be classified as having alcoholic fatty liver disease. This review summarises a presentation given at the symposium 'The liver in focus' at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by Kenneth Cusi, DOI: 10.1007/s00125-016-3952-1 , and by John Jones, DOI: 10.1007/s00125-016-3940-5 ) and a commentary by the Session Chair, Michael Roden (DOI: 10.1007/s00125-016-3911-x ).