Alternative Names SGPT, serum glutamate pyruvate transaminase, alanine transaminase
Definition This test determines the level of the enzyme alanine transaminase (ALT) in the blood. Abnormally high levels of ALT may indicate liver damage.
ALT is an enzyme that takes part in the metabolism (chemical processing by the body) of the amino acid, alanine. ALT is present in many different kinds of tissue in the body. However, it is highly concentrated in the liver. Therefore, when the liver is injured, ALT is released into the bloodstream.
How is the test performed? A blood sample needs to be taken in order to measure the level of ALT. The blood is usually drawn from a vein in the forearm or the hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube called a tourniquet is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A very thin needle is gently inserted into a vein and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial. The sample is sent to the laboratory to be analysed. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
What is involved in preparation for the test? Individuals should request specific instructions from their doctor on how to prepare for this test.
What do the test results mean? Normally, ALT levels range from 6 to 45 units per litre (U/L).
If ALT levels are higher than normal, that may indicate one of several types of liver damage. Possibilities include congestion of the bile ducts (cholestasis), cirrhosis (scarring and loss of liver function), hepatitis (liver inflammation), liver blood deficiency (hepatic ischemia), death of liver tissue (hepatic necrosis), liver tumour, or use of drugs toxic to the liver. Typically, in alcoholic liver disease, the AST is elevated more than the ALT test.
Author: David T. Moran, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 6/06/2005 Contributors Potential conflict of interest information for reviewers available on request
