AST and ALT - Cholesterol Test Descriptions

ALT (Liver Function Cell Damage)
ALT is measured to determine whether the liver is damaged or diseased. Low levels of ALT are normally found in the blood. However, when the liver is damaged or diseased, it releases ALT into the bloodstream, causing levels of the enzyme to rise. Although ALT is found in organs other than the liver, most increases in ALT levels are due to liver damage. The ALT test often is done along with other tests that can determine whether the liver is damaged, including aspartate aminotransferase (AST). Both ALT and AST levels are reliable indicators of liver damage.

AST (Liver Function Tissue Damage)
When an organ (such as the heart or liver) or body tissue is diseased or damaged, additional AST is released into the bloodstream. The amount of AST in the blood is directly related to the extent of the tissue damage. After severe damage, AST levels rise in 6 to 10 hours and remain high for about 4 days. The AST test may be done at the same time as a test for alanine aminotransferase, or ALT. The ratio of AST to ALT (AST:ALT) sometimes can help determine whether the liver or another organ has been damaged. AST also can help determine the cause of the liver damage. Both ALT and AST levels are reliable indicators of liver damage.

What is ALT?
ALT (Alanine Aminotransferase) is an enzyme that appears in liver cells, with lesser amounts in the kidneys, heart, and skeletal muscles, and is a relatively specific indicator of acute liver cell damage. When such damage occurs, ALT is released from the liver cells into the bloodstream, often before jaundice appears.

What is AST?
AST (Aspartate Aminotransferase) is found in many body tissues including the heart, muscle, kidney, brain, and lung. It is also present in the liver. When body tissue or an organ such as the heart or liver is damaged, additional AST is released into the bloodstream. The amount of AST in the blood is directly related to the extent of the tissue damage.

What is the purpose of the blood serum test?
ALT and AST are elevated even before the clinical signs and symptoms of disease, such as cardiovascular disease, liver disease and muscle disease. The purpose of the blood serum test is to help detect and evaluate treatment of acute hepatic disease, especially hepatitis, and cirrhosis without jaundice. An inflamed liver is called hepatitis. Trauma can cause this, along with drugs (even aspirin), viruses, bacteria, bile, and toxins. Many medications produce hepatic injury by competitively interfering with cellular metabolism.
To help distinguish between myocardial (heart) and jaundice (liver tissue).
Also to assess hepatotoxicity of some drugs.