Aspartate Aminotransferase (AST, GOT)

Aspartate aminotransferase (AST, ASAT; also called glutamate oxaloacetate transaminase (GOT)) is an enzyme produced primarily in hepatocytes (liver cells). It is thus a very sensitive marker for parenchymal liver damage. Aspartate aminotransferase, like alanine aminotransferase (ALT, ALAT; also called glutamate pyruvate transaminase (GPT)), belongs to the transaminases. These are enzymes that catalyze the transfer of α-amino groups from a donor to an acceptor molecule (transamination). AST (GOT) is not liver specific. It is a ubiquitous (“ubiquitous”) enzyme and is found predominantly in the liver, kidneys, myocardium (heart muscle), and skeletal muscle and is localized in the cytoplasm (basic structure filling the cell) and mitochondria (” powerhouses of cells”). AST elevations occur in liver disease, myocardial infarction (heart attack), and skeletal muscle damage.

The procedure

Material needed

  • Blood serum

Preparation of the patient

  • Not necessary

Disruptive factors

  • Avoid hemolysis (dissolution of red blood cells)! This leads to the highly pathological increase of AST (AST is 15 times higher in erythrocytes (red blood cells) than in the serum!)
  • Strong muscle work
  • Supplements containing red rice or green tea may cause abnormal changes in liver enzymes.
  • Medications (see under “Hepatotoxic Medications”).

Normal values

Gender Normal values in U/l according to old reference range (measurement 25 °C) Normal values in U/l according to new reference range (measurement 37 °C)
Female < 15 10-35
Male < 19 10-50
Newborn, 1st month of life 6-38
2nd-12th month of life 7-27
> 1. year of life 5-22

Indications

  • Diagnosis, differentiation and follow-up of liver and biliary tract diseases.
  • For differential diagnostic clarification, etiology clarification, and assessment of disease severity and stage.
  • For prognostic assessment of muscle damage in myocardial infarction.

Interpretation

Interpretation of increased values

  • Alcohol dependence [AST > ALT]
  • Acute circulatory disorder
  • Acute hepatitis (liver inflammation) [ALT > AST]
  • Alpha-1 antitrypsin deficiency [ALT > AST]
  • Autoimmune hepatitis (AIH; autoimmune hepatitis) (esp. women) [ALT > AST]
  • Cholangitis (biliary tract inflammation).
  • Cholestasis (bile stasis)
  • Cholecystitis (gallbladder inflammation)
  • Chronic hepatitis (inflammation of the liver)
  • Genetic diseases* such as muscular dystrophy, cystic fibrosis (cystic fibrosis) progressive muscular dystrophy, celiac disease (gluten-induced enteropathy; chronic disease of the mucosa of the small intestine (small intestinal mucosa) due to hypersensitivity to the cereal protein gluten).
  • Hemochromatosis (iron storage disease) [ALT> AST]
  • Infections (after foreign travel)
  • Liver metastases
  • Liver tumors
  • Liver cirrhosis – connective tissue remodeling of the liver with resulting functional impairment.
  • Pulmonary embolismocclusion of blood vessels supplying the lungs by an embolus (blood clot).
  • Mononucleosis (Pfeiffer’s glandular fever) – infectious disease caused by the Epstein-Barr virus (EBV).
  • Wilson’s disease (copper storage disease) [ALT > AST]
  • Hemochromatosis (iron storage disease) [ALT> AST]
  • Muscle diseases such as myositis (muscle inflammation).
  • Myocardial infarction (heart attack)
  • Myocarditis (inflammation of the heart muscle) [diagnostic sensitivity (percentage of diseased patients in whom the disease is detected by use of the test, i.e., a positive test result occurs) 96%, diagnostic specificity (probability that actually healthy individuals who do not have the disease in question are also detected as healthy in the test) 80% 12 hours after the acute event].
  • Primary biliary cholangitis/biliary duct inflammation (PBC, synonyms: nonpurulent destructive cholangitis; formerly primary biliary cirrhosis); detection of antimitochondrial antibodies (AMA).
  • Steatosis hepatis (fatty liver) [nonalcoholic fatty liver: ALT > AST]
  • Trauma (injuries)
  • Toxic//medical liver injury (see “Hepatotoxic drugs” below).
  • Viral hepatitis (virus-related liver inflammation).
  • Celiac disease (in 5-10% of cases).

* Ca. 12% of isolated aminotransferases elevation of a pediatric clinic.

Interpretation of decreased values

  • Not relevant to disease

Further notes

  • Intraindividual variation in aminotransferases is approximately 10-30% from day to day; increased activities may also be measured during vigorous exercise.
  • De-ritis quotient (= AST/ALT) allows conclusions about the severity of hepatocyte damage in liver disease:
    • acute hepatitis:
      • <1: uncomplicated course
      • > 1: complicated course
      • – 2: alcoholic hepatitis
    • chronic hepatitis:
      • < 1 (common); elevated ALT (GPT) levels > 6 months → chronic hepatitis.
    • Liver cirrhosis:
    • Non-hepatic (trauma/myocardial infarction): > 1
  • Diagnostic sensitivity of AST is poorer than ALT (GPT) in liver disease, approximately 70%.
  • AST (GOT) is mainly localized in the mitochondria (80%), but is also present in the cytoplasm (20%):
    • Mild liver damage → membrane-bound gamma-GT ↑
    • Moderate liver damage → cytoplasmic ALT (GPT) ↑ and AST (GOT) ↑
    • Severe liver damage → mitochondrial GLDH ↑ and AST (GOT) ↑
  • The half-life is 17 h.

Further diagnostics

  • Alanine aminotransferase (ALT, GPT), glutamate dehydrogenase (GLDH), gamma-glutamyl transferase (gamma-GT), alkaline phosphatase (AP), and bilirubin should always be measured to determine liver function.Simultaneous determination of AST, ALT, and γ-GT can detect more than 95% of all liver diseases.
  • Further diagnostic testing for elevated liver values is indicated when:
    • Chronic (> 6 months) existing
    • Symptomatic
    • Exceeding three times the norm
  • Basal workup for elevated liver enzymes – the most common causes are nonalcoholic fatty liver disease (NAFLD) or alcohol abuse – includes mandatory liver sonography and screening for chronic hepatitis B and C!