Lab Test: Aspartate Aminotransferase, AST Level
- Aspartate aminotransferase (AST)
- Synonyms: glutamic oxaloacetic transaminase measurement, GOT measurement SGOT measurement
- Measurement of aspartate aminotransferase in serum for the evaluation of liver, heart, and other systemic diseases.
- Adults: 0-35 units/L (0-0.58 microkat/L). Females tend to have slightly lower levels than males.
- Strenuous exercise: up to 25% increase of normal value
- Elderly: slightly higher than adults
- 12-18 years: 10-40 units/L
- 6-12 years: 10-50 units/L
- 3-6 years: 15-50 units/L
- <3 years: 15-60 units/L
- 0-5 days: 35-140 units/L
- Hantavirus pulmonary syndrome - often mildly elevated at the time of admission and increases during the hospital course. Levels rise to 2 to 5 times the upper limit of normal as clinical picture worsens.
- Indicator of pancreatic necrosis in acute pancreatitis - AST levels > 250 IU/L
- Sickle cell disease - increased in certain complication of sickle cell disease such as obstructive cholelithiasis transfusion hepatitis, acute hepatic crisis, and transfusion hemosiderosis.
- Suspected blunt abdominal trauma - AST level > 450 units/L is associated with liver injury in children with BAT. Elevation of serum AST and ALT levels is a marker foe intra-abdominal injury in BAT patients and an indication for obtaining an abdominal CT.
- Suspected cholecystitis - Increase AST levels, typically less than 5 times the normal value, are commonly seen in cholecystitis. Should be drawn during the acute phase of the illness as values typically return to normal within one week after symptoms resolve.
- Suspected drug-induced liver disease - Marked elevations in AST levels. In alcoholic liver injury, the AST stays below 300 IU/L, the ALT is < 100 IU/L, and a 2:1 or 3:1 ratio is maintained. Liver injury attributable to alcohol should be suspected if the AST level is greater than the ALT level by a ratio of 2:1. Biochemically, acetaminophen toxicity is associated with levels of AST and ALT often exceeding 10,000 IU/L.
- Suspected ehrlichiosis -mild to moderate increases in AST. AST levels should be drawn during the first week of the acute illness as mild to moderate elevations are noted in about 85% of patients.
- Suspected inflammatory liver disease or hepatitis - Increase serum aminotransferase levels are suggestive of acute viral hepatitis. Markedly increased levels suggest hepatocellular necrosis in acute and chronic liver disease. Suspected Reye's syndrome - AST is typically elevated 1.5 to 2 times normal in this syndrome.
- Creatine kinase (CK) - exists primarily in heart and skeletal muscle.
- Alanine aminotransferase (ALT) - exists primarily in the liver.
- Lactic dehydrogenase (LDH) - intracellular enzyme used to support the diagnosis of injury or disease involving the heart, liver, RBCs, kidneys skeletal muscle, brain, and lungs.
- Leucine aminopeptidase (LAP) - specific to the hepatobiliary system.
- Gamma-glutamyl transpeptidase (GGTP) - exists primarily in the liver.
- Alkaline phosphatase - exists primarily in the liver. 5'-nucleotidase - exists primarily in the liver.
- Pregnancy may cause decreased AST levels.
- Exercise may cause increased levels.
- Levels are falsely decreased in patients with pyridoxine deficiency (beriberi, pregnancy), severe long-standing liver disease, uremia, or diabetic ketoacidosis.
- Drugs that may cause increased levels include: antihypertensive, cholinergic agents, Coumarin-type anticoagulants, digitalis preparations, erythromycin, hepatotoxic medications, isoniazid, methyldopa, oral contraceptives, opiates, salicylates stains, and verapamil.
- Avoid giving the patient any intramuscular (IM) injection. If possible, hold the drugs that could interfere with test results for 12 hours before the test. Collect a venous sample of blood. This is usually done daily for 3 days and then again in 1 week.
- Rotate the venipuncture site and avoid hemolysis.
- Indicate on the laboratory slip any drugs that may cause false-positive results and record the time and date of any intramuscular injection given.
- Record the exact time and date when the blood test is performed. This aids in the interpretation of the temporal patter of enzyme elevations. Apply pressure or a pressure dressing to the venipuncture site and observe the site for bleeding.
This enzyme is found in very high concentrations within highly metabolic tissue, such as the heart muscle, liver cells, skeletal muscle cells, and to a lesser degree in the kidneys, pancreas, and red blood cells (RBCs). When disease or injury affects the cells of these tissues, the cells lyse. The AST is released picked up by the blood, and the serum level rises. The amount of the AST elevation is directly related to the number of cells affected by the disease or injury. The elevation also depends on the length of time that the blood is drawn after the injury, since AST is cleared from the blood in a few days. Levels become elevated 8 hours after cell injury, peak at 24 to 36 hours, and return to normal in 3 to 7 days.
Serum AST levels are often compared with ALT levels.
Individual AST assays, used in isolation, do not discriminate well among the various diseases affecting the liver and biliary tree. The magnitude of elevation and rate of change of aminotransferase alteration may aid in the differential diagnosis.
MESH Terms & Keywords