We explained above that there are different sub-types of liver disease. NAFLD is a metabolic disorder and can be classified into two main types; NAFL and NASH. NAFLD is the most common cause of chronic liver disease in the Western World. NAFL and NASH are caused by a build-up of fat in the liver, which is also called ‘steatosis’. NAFL is considered a milder form of the disease that may never progress to NASH, and can often be managed with lifestyle intervention. NASH, however, is a more pathogenic form that can cause severe damage to the liver in the form of scarring, known as fibrosis, and in some cases can result in hepatocellular carcinoma (HCC). Approximately 10-20% of those with NAFLD will develop NASH, and a small subset may progress more rapidly than others.

To clinically define NAFLD, there must be evidence of fat accumulation (steatosis) on the liver (confirmed by imaging or histology), in the absence of other causes of fat accumulation such as alcohol consumption. In cases where there is fat accumulation in the presence of excessive alcohol intake, this is known as Alcoholic Liver Disease (ALD). When doctors decide between a diagnosis of NAFL or NASH, their decision stems from assessing the health of the liver cells, called hepatocytes. NAFL is defined as greater than 5% steatosis of the liver without injury to the hepatocytes (hepatocyte injury is routinely established using serum biomarkers and less commonly biopsy). Establishing a diagnosis of NASH is much more challenging but is often based on the presence of inflamed or damaged hepatocytes which may or may not be accompanied by fibrosis (extremely damaged hepatocytes)³.