Pre-emptive testing

Liver function tests measure chemicals in the blood made by the liver. An abnormal result indicates a liver problem, and may help to identify the cause of it. Further tests may be needed to clarify the cause of the liver problem.

As the liver performs its various functions it makes a number of chemicals that pass into the bloodstream and bile. Several liver disorders alter the blood level of these chemicals. Some of these can be measured in a blood sample. Some tests that are commonly done on a blood sample are called liver function tests.

These LFTs usually measure the following.

* Alanine transaminase (ALT). This is an enzyme that helps to process proteins. (An enzyme is a protein that helps to speed up chemical reactions. Various enzymes occur in the cells in the body). Large amounts of ALT occur in liver cells. When the liver is injured/ inflamed (as in hepatitis), the blood level of ALT usually rises.

- Alkaline phoshpatase (ALP). This enzyme occurs mainly in liver cells next to bile ducts, and in bone. The blood level is usually raised in some types of liver and bone disease.

- Albumin. This is the main protein made by the liver, and it circulates in the bloodstream. The ability to make albumin (and other proteins) is affected in some specific types of liver disorder. Low level of blood albumin occurs in some liver disorders.

- Total Protein. This measures albumin and other proteins in blood.

- Bilirubin. This chemical gives bile its yellow colour. A high level of bilirubin in blood will make a person jaundiced. Bilirubin is made from haemoglobin. Haemoglobin is a chemical in red blood cells that is released when the red blood cells breaks down. Liver cells take in bilirubin and attach sugar molecules to it. This is then called conjugated bilirubin which is passed into the bile ducts.

- A raised blood level of 'congugated' bilirubin occurs in liver and bile duct conditions. It is particularly high if the flow of bile is blocked.

Use of Liver Function Tests

- To help diagnose liver disorders for suggestive symptoms (such as jaundice). The pattern of the blood results may help to say which disorder is causing the problem. For example, depending on which enzyme is highest it may point to a particular disorder.
- To monitor the activity and severity of liver disorders
- As a routine precaution after starting some medicines to check that they are not causing liver damage as a side-effect.