A Comprehensive Metabolic Panel, or CMP, is a group of 12 to 20 blood tests used to screen for a wide variety of medical disorders. The presence or absence of liver, kidney or other diseases may be determined based on the pattern of results. Aspartate aminotransferase, AST, also known as serum glutamic oxaloacetic transaminase, or SGOT, is one of the tests in the panel.
A phlebotomist collects the blood sample, most commonly by needle puncture of an arm vein. The sample is transported to the laboratory, where it is analyzed using an automated instrument. Your health practitioner should be aware of any special diet, alcohol use or herbal supplements being taken, and may give specific instructions regarding food intake or drug use prior to the test being performed.
AST is an enzyme found in many sites of the body. The greatest concentrations are found in heart muscle, followed by liver, skeletal muscle, kidney, and brain in decreasing order. When damage occurs to any of these tissues, increased amounts of AST are released and enter the bloodstream. Normal blood levels vary slightly by laboratory, age and sex, ranging from approximately 10 to 50 U/L as reported by the Mayo Clinic Laboratories.
Elevated AST Levels
Elevated levels of AST are non-specific, and may be seen with injury or disease involving any of its source tissues. According to "Clinical Diagnosis and Management by Laboratory Methods," AST elevations are most often seen in heart and liver disorders. Acute myocardial infarction, congestive heart failure, pulmonary infarction and pericarditis are examples of the former. Inflammation or destruction of skeletal muscle in cases of progressive muscular dystrophy, dermatomyositis or crush injuries will also result in elevations. Many other sites of tissue damage may cause lesser increases in AST.
AST is a sensitive marker for liver damage, and is used in both diagnosis and monitoring of liver disease. LabTestsOnline.org states that marked elevations of AST are usually caused by acute hepatitis. Levels also rise with alcohol damage, chronic hepatitis, infectious mononucleosis and metastatic cancer to the liver. AST testing may be used to monitor for the development of drug toxicity in patients taking medications with possible liver side effects.
Because elevated AST levels may result from such a wide variety of possible causes, any abnormal result must be interpreted in conjunction with other tests performed, medical history and physical examination. Additional liver function tests, including alanine aminotransferase, or ALT, alkaline phosphatase, bilirubin and protein levels will usually be performed, as well as other tests and studies, as necessary.