aspartate aminotransferase (AST) in serum (SGOT)

Indications

• evaluation of
  • viral hepatitis
  • alcoholic hepatitis
  • drug induced hepatitis
  • autoimmune hepatitis
  • non-alcoholic steatohepatitis (NASH)
  • myocardial infarction
  • pulmonary embolism
  • skeletal muscle trauma
  • alcoholic cirrhosis

Reference interval

• Male & Female: 5-40 U/L

Principle

The Kodak Ektachem Clinical Chemistry Slide (AST) is a dry, multilayered analytical element coated on a clear polyester support.

An 11 uL drop of sample is deposited on the slide & evenly distributed by the spreading layer. In the assay for Aspartate Aminotransferase (AST), the amino group of Aspartate is transferred to a-ketoglutarate in the presence of sodium pyridoxal-5-phosphate (P5P) to produce glutamate & oxaloacetate. The oxaloacetate formed in the deamination of the L-aspartate is converted to malate by malate dehydrogenase (MDDH) in the presence of NADH, which is oxidized to NAD+. The rate of oxidation of NADH is monitored by reflectance spectrophotometry. The rate of change in reflection density is measured in linear region & then converted to enzyme activity.

The following reaction sequences are involved:

                             AST
Aspartate + a-ketoglutarate  ----->  Oxaloacetate + Glutamate
                             P5P

                            malate
                            dehydrogenase
Oxaloacetate + NADH + H+    ------------>     Malate +  NAD+

Clinical significance

• AST is present in all body tissues with high activities in the heart, skeletal muscle, liver & erythrocytes
  • minimal activityis found in skin, kidney & pancreas
• an increased serum AST is commonly observed following myocardial infarction, pulmonary emboli, skeletal muscle trauma, alcoholic cirrhosis, viral hepatitis, & drug induced hepatitis
• in alcoholic hepatitis & after acute myocardial infarction, serum AST is generally > serum ALT
• in viral hepatitis, serum ALT is generally > serum AST

• serum AST is generally normal after IM injections or moderate exercise.

• in blunt abdominal trauma in children, serum AST> 450 U/L is a good predictor of liver injury
• in adults, serum AST peaks within 24 hours & rapidly declines over the next 4 days
  • prolonged elevations should be investigated

• serum IgA-AST complexes are frequently associated with liver malignancies

Increases

• large increases
  • fulminant hepatitis
    • acute viral hepatitis
    • acute autoimmune hepatitis
    • hepatic ischemia
• clinical disorders with lesser increases
  • liver injury
    • cholestatic & obstructive jaundice
    • chronic hepatitis
    • alcoholic hepatitis (AST > ALT)
    • chronic viral hepatitis (ALT > AST)
  • hepatic metastases & hepatoma
  • infectious mononucleosis
  • necrosis or trauma to heart or skeletal muscle
  • inflammatory disease of heart or skeletal muscle
  • adult-onset Still's disease
  • severe exercise
  • heart failure
  • severe burns
  • Forbe's disease (children, not adults)
  • heat stroke (20-fold)
  • hypothyroidism
  • intestinal obstruction or infarction
  • lactate acidosis
  • legionnaire's disease
  • malignant hyperthermia
  • postcommissurotomy
  • polymyalgia rheumatica
  • typhoid fever
  • thalassemia major
  • von Gierke's disease
  • toxic shock syndrome
  • celiac disease
• may or may not be increased in:
  • cirrhosis
  • neurologic disease
  • cerebral infarction or hemorrhage
  • acute pancreatitis
  • renal infarction
  • hemolytic anemia
  • hemophilia
  • malnutrition
  • obesity
• pharmaceutical agents:
  • in vivo effects
    • see drugs that may affect liver function tests (LFTs)
    • acebutolol, aminoglutethamide, aminoglycosides, azithromycin, ampicillin, bromocryptine, captopril, carboplatin, carmustine, cephalosporins, clindamycin, clofibrate, clotrimazole, colchicine, cyclosporine, cytarabine, dacarbazine, dapsone didanosine, disopyramide, enflurane, ethacrynic acid, ethambutol, etoposide, fenofibrate, fluoroquinolones, ganciclovir, gentamicin, heparin, statins, idarubicin, interferon, isotretinoin, labetolol, levamisole, levodopa, lincomycin, mebendazole, mefloquine, metoprolol, methyltestosterone, nafcillin, nifedipine, omeprazole, opiates, oxacillin, penicillins, pentamidine, piroxicam, propoxyphene, protriptyline, pyridixine, ranitidine, ritodrine, sargramostim, streptozocin, sulfonylureas, thiothixene, thiabendazole, thioguanine, ticlopidine, tobramycin, tretinoin, verapamil, zalcitabine

Specimen

No special patient preparation is necessary.

Sample Preparation: Collect the specimen by st&ard venipuncture technique. The specimen should be free from hemolysis & cellular material. Heparin may be used as an anticoagulant for plasma specimens. EDTA & Sodium fluoride/ Potassium Oxalate should not be used as an anticoagulant. Remove serum & plasma promptly from the clot of cells. Handle specimens in stoppered containers to avoid contamination & evaporation. Refrigerate at 2-8 C if analysis is not performed within 4 hours.

There is a clinically significant difference between results obtained on fresh plasma centrifuged for five minutes & fresh serum. To avoid cellular material in plasma, all specimens should be centrifuged at 1000 Xg for a minimum of 10 minutes.

Minimum sample size 0.5 milliliter: with an optimum size of 1.0 milliliter or larger.

Interferences

• Heparin activities at greater than 50 U/L have been reported to cause a positive bias.s method.
• Elevated total protein associated with a larger percentage of immunoglobulins in samples from multiple myeloma patients may cause higher than expected results. Dilute samples from multiple myeloma patients with an equal volume of isotonic saline before analysis.
• Samples with bilirubin concentration greater that 25.0 mg/dL & with AST activities less than 10 U/L can interfere with the substrate depletion flag. Dilute these samples with an equal volume of isotonic saline & reanalyze. Multiply result by two to obtain the original sample's AST activity.

More general terms

• aspartate aminotransferase (AST) in body fluid
• liver (function) tests (LFT, liver panel, hepatic function panel)

More specific terms

• aspartate aminotransferase, macromolecular in serum

Additional terms

• aspartate aminotransferase (AST), glutamine/oxaloacetate transaminase (GOT, SGOT) or transaminase A
• drugs that may affect liver function tests (LFTs)
• elevated serum transaminases; transaminitis; abnormal liver function tests

Component of

• chemistry 14 panel (comprehensive metabolic panel, CMP, chem 12, SMA12, SMA20)
• gamma glutamyltransferase/aspartate aminotransferase in serum/plasma
• alanine aminotransferase (ALT)/aspartate aminotransferase (AST) in serum/plasma
• aspartate aminotransferase/alanine aminotransferase in serum
• aspartate aminotransferase, macromolecular/aspartate aminotransferase, total in serum
• liver (function) tests (LFT, liver panel, hepatic function panel)

Patient information

aspartate aminotransferase (AST) patient information