Liver function tests
Liver function tests are used to detect liver damage or disease. Combinations of up to five tests are measured at the same time on a blood sample. These are selected from:
- Alanine aminotransferase (ALT) – an enzyme mainly found in the liver; the best test for detecting hepatitis
- Alkaline phosphatase (ALP) – an enzyme related to the bile ducts; often increased when they are blocked
- Aspartate aminotransferase (AST) – an enzyme found in the liver and a few other places, particularly the heart and other muscles in the body
- Total bilirubin – measures all the yellow bilirubin pigment in the blood. Another test, direct bilirubin, measures a form made in the liver and is often requested with total bilirubin in infants with jaundice.
- Albumin – measures the main protein made by the liver and tells how well the liver is making this protein
- Gamma-glutamyl transferase (GGT) - an enzyme found mainly in the liver and is a useful marker for detecting bile duct problems
- Total protein - measures albumin and all other proteins in blood, including antibodies made to help fight off infections
Other tests that can be used to assess liver function include a coagulation screen, together with bilirubin and urobilinogen in urine
How are the results interpreted?
The pattern of the test results together with information about the patient’s symptoms can give an idea of what type of liver disease is present. Note that abnormal results for some of these tests can be caused by diseases other than liver disease. Further specific testing than then be performed if necessary e.g. hepatitis virus testing or even a liver biopsy.
When are these tests requested?
These tests are used when symptoms suspicious of a liver condition are noticed. These include:
- jaundice
- dark urine and light-coloured bowel movements
- nausea, vomiting and diarrhoea
- loss of appetite
- vomiting of blood
- bloody or black bowel movements
- swelling or pain in the belly
- unusual weight change, or
- fatigue or loss of stamina.
One or more of these tests may be requested when a person has been or may have been exposed to a hepatitis virus, has a family history of liver disease, has excessive alcohol intake, or is taking a drug that can cause liver damage.
Related websites
RCPA Manual
Australian Hepatitis Council
