Patients have liver function tests checked for a variety of reasons both in the community and in hospital settings. Liver tests can be acutely or chronically deranged and can be abnormal for a number of reasons. A ‘liver screen’ is commonly requested to investigate abnormal liver functions tests. The screen can be modified depending on the age of the patient and whether acute or chronic liver disease is suspected.
A careful history is vital. Salient points in the history should be:
A thorough examination should include:
It is useful to look at the pattern of abnormal liver function tests to see if they are predominantly hepatitic, cholestatic or there is hyperbilirubinaemia. Sometimes there is a mixed pattern. The pattern of abnormality in the liver function tests can help guide investigations.
Alanine transaminase (ALT) and aspartate transaminase (AST) are markers of hepatocellular injury. AST is also found in other organs including cardiac and skeletal muscle so is less sensitive or specific for liver injury.
A significantly raised ALT of >1000 U/l is seen in only a limited number of conditions:
Typically characterised by rapid, massive increase in liver enzymes when hepatic blood flow is insufficient
Drug-induced liver injury
A detailed medication history should be taken in all patients, dating back at least 6 months. This should include prescribed medications, OTC, herbal remedies and illicit drugs
A number of medications can cause a rise in transaminases, some of the commonest are: Statins, NSAIDs, anti-epileptic medications, anti-tuberculous medications, methotrexate.
Acute biliary obstruction
Patients with acute biliary obstruction may benefit from urgent endoscopic decompression, necessitating early consideration of this diagnosis
Other causes of raised transaminases are:
Non-alcoholic fatty liver disease (NAFLD)
Alcohol-related liver disease
Other liver-related causes of raised transaminases are:
There are many other causes of raised transaminases including:
Cholestatic liver tests will show a predominant rise in alkaline phosphatase +/- a rise in bilirubin. Alkaline phosphatase (ALP) originates from bone and liver and it is important to understand this. Checking gammaglutamyl transferase (GGT) can be useful as this will be raised in liver but not bone causes of a raised ALP. Some laboratories can do ALP iso-enzymes which can differentiate liver / bone origin.
Liver causes of cholestatic liver tests are:
Extra-hepatic biliary obstruction
Primary Biliary Cholangitis (PBC)
Primary Sclerosing Cholangitis (PSC)
Hepatic congestion (e.g. cardiac failure)
Jaundice is caused by accumulation of bilirubin in the bloodstream. It becomes apparent when there is deposition in the skin, sclera and mucous membranes. The causes of jaundice can be divided into:
Isolated raised bilirubin