ALT concentrations can fluctuate with chronic hepatitis, not all patients will have a raised level.  Moderately elevated levels can occur with high alcohol consumption, in diabetic patients, with hyperlipidaemia all of which can cause fatty liver disease. Patients with cirrhosis, non-alcoholic steatohepatitis, cholestatic liver disease, fatty liver and hepatic tumours typically have a slightly raised ALT. Other causes include haemochromatosis, autoimmune hepatitis, primary biliary cirrhosis and thyroid disorders.

Analysing the relationship between AST and ALT, (AST: ALT ratio) is often useful; it can be suggestive of certain conditions as there is considerable overlap. However, it is not exclusive and only serves as an aid to clinical decision-making.  If the AST:ALT ratio is greater than two, it is more suggestive of alcoholic liver disease. In contrast, viral hepatitis causes ALT to rise more than AST, and the ratio is usually <1, particularly true of hepatitis C.  In Wilson’s disease can cause the AST/ALT ratio to exceed 4.

Transaminases 2-5 times the upper limit of normal are often seen in chronic viral hepatitis and non-alcohol steatohepatitis (NASH). Transaminases are rarely > 10 times the upper limit of normal in uncomplicated alcoholic hepatitis. Transaminases > 20 times can indicate acute viral infection, ischaemic hepatitis, drug or paracetamol toxicity.