Non-alcoholic fatty liver disease (NAFLD) represents a spectrum of liver disease encompassing simple fatty infiltration (steatosis), fat and inflammation (non-alcoholic steatohepatitis (NASH)), and cirrhosis, in the absence of excessive alcohol consumption (typically a threshold of <20 g a day for women and <30 g a day for men is adopted). Simple steatosis has not been associated with liver related morbidity, but NASH may lead to progressive liver fibrosis, cirrhosis, and liver cancer, as well as increase cardiovascular risk. NAFLD is strongly associated with obesity, insulin resistance or type 2 diabetes mellitus, and dyslipidaemia and may be considered the hepatic manifestation of the metabolic syndrome.1 2 Estimates vary between populations, but one large European study found NAFLD in 94% of obese patients (body mass index (kg/m²) >30), 67% of overweight patients (>25), and 25% of normal weight patients.3 The overall prevalence of NAFLD in people with type 2 diabetes ranges from 40% to 70%.3 With the advent of increasingly sedentary lifestyles and changing dietary patterns, the prevalence of obesity and insulin resistance have increased and NAFLD has rapidly become the most common cause of abnormal liver biochemistry in many developed countries.4 Despite substantial clinical and basic research in this field, the true prevalence of NAFLD and NASH in the community and the likely future disease burden remain unclear. Furthermore, clinical uncertainties persist from diagnosis and risk stratification through to treatment and long term follow-up.

Diagnosis and risk stratification—Much of the population is at risk of NAFLD through being overweight or insulin resistant, or both, but how best to identify patients with NAFLD remains unclear, especially in patients with NASH, who are at greatest risk of liver related complications. Many patients remain undiagnosed and so it is not known what the true prevalences of steatosis and …