These are enzymes that are indicators of liver cell damage. When such damage occurs, ALT is released from the liver cells into the bloodstream, often before jaundice appears, resulting in abnormally high serum levels that may not return to normal for days or weeks. The purpose of this blood serum test is to help detect and evaluate treatment of acute hepatic disease, especially hepatitis, and cirrhosis without jaundice. Also to assess hepatotoxicity of some drugs. The normal range for infants is twice that of adults.
Many medications produce hepatic injury by competitively interfering with cellular metabolism.
Tests commonly referred to as liver function tests or LFT's do not actually determine liver function. Instead, they are static, primarily diagnostic parameters that serve to detect liver disease rather than quantitative liver function. Rather than liver function tests, it is more useful to refer to these tests as serum liver tests and to mentally categorise them according to the pathophysiologic processes they truly reflect. Thus, the relative change in AST values serves as a reliable monitoring mechanism. Maximum elevations are associated with certain diseases and conditions.