Aspartate Aminotransferase
Test Description Aspartate aminotransferase (AST) is an enzyme found primarily in the heart, liver, and muscle. It is released into the circulation after injury or death of cells. AST levels usually increase within 12 hours of the injury and remain elevated for 5 days. Thus, this test is one of several that are performed when there has been damage to the heart muscle, as in myocardial infarction, and in assessing liver damage. Other cardiac enzymes also assessed are the creatine kinase (CK) isoenzymes, lactic dehydrogenase (LDH, LD), and troponin. AST is assessed along with alanine aminotransferase (ALT) in monitoring liver damage. These two values normally exist in an approximately 1:1 ratio. The AST is greater than the ALT in alcohol-induced hepatitis, cirrhosis, and metastatic cancer of the liver. ALT is greater than AST in the case of viral or drug-induced hepatitis and hepatic obstruction due to causes other than malignancy. The degree of increase in these enzyme...