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Test Code LAB4018 ASPARTATE AMINOTRANSFERASE (AST)

Important Note

Useful for:

  • Alcoholic hepatitis (AST > ALT)
  • Early acute hepatitis - AST is usually higher initially but after 48 hours, ALT is usually higher
  • Levels of 500  U/L suggest acute hepatocellular injury, seldom >500 U/L in obstructive jaundice, cirrhosis, viral hepatitis, AIDS, and alcoholic liver disease
  • Acute fulminant viral hepatitis - Abrupt AST rise may be seen but rarely > 4,000 U/L; and declines more slowly
  • Congestive heart failure, arrythmia, sepsis, and GI hemorrhage AST levels reach to a peak of 1,000-9,000 U/L declining by 50% within 3 days and to < 100 U/L within 1 week, suggesting liver shock with centrolobular necrosis. Bilirubin and ALP may refelct underlying disease. 
  • Acute heart failure (AST > ALT)
  • Severe exercise, burns, hypothyroidism, biliary obstruction and heat stroke
  • Drug-induced injury to the liver

Additional Codes

Labcorp 001123

Synonyms

SGOT

Specimen Type

Preferred Sample: Lithium Heparin Plasma (Light Green Top)
Alternative Sample:  Serum Tube (SST, Gold, Corvac, Tiger, Red Top Tube)

Specimen Volume

Preferred: 1.0 mL

Minimum: 0.5 mL

Sample Stability

Room Temp: 4 days
Refrigerated: 7 days

Frozen: 12 weeks (-20C)

Clinical Information

Aspartate aminotransferase (AST), also referred to as glutamate oxaloacetate transaminase (GOT), catalyzes the deamination of the amino acid aspartate, one of the steps involved in the metabolism of proteins for energy. It is found in a variety of tissues, mainly the liver, heart, muscles, and kidneys. Damage to these tissues can greatly elevate serum AST levels. Serum values may increase to 10 to 15 times normal levels and the increase is roughly proportional to the degree of tissue damage. Following myocardial infarction, AST in serum begins to increase within 6 to 8 hours of onset of pain, reaching a peak within 18 to 24 hours and falling to normal by the fourth or fifth day.

 

Hepatic diseases also show elevated AST levels and are evaluated in conjunction with alanine aminotransferase (ALT) levels since ALT is more liver specific. The DeRitis ratio (AST/ALT quotient) is found to be elevated in alcohol-induced liver disease, viral hepatitis, cirrhosis and acute fulminant hepatic failure. A ratio of greater than two suggest that alcohol is the cause of liver injury. Neonates and children younger than 3 years old have serum AST levels twice that of adults.

Method

Enzymatic (NADH (without P-5'-P))

 

AST present in the sample catalyzes the transfer of the amino group from L-aspartate to α ketoglutarate, forming oxaloacetate and L-glutamate. Oxaloacetate in the presence of NADH and malate dehydrogenase (MDH) is reduced to L-malate. In this reaction, NADH is oxidized to NAD+. The reaction is monitored by measuring the rate of decrease in absorbance at 340 nm due to the oxidation of NADH to NAD+.

Limitations

  • Interferences from medication or endogenous substances may affect results.
  • Avoid hemolyzed specimens due to high AST levels found in red blood cells. Specimens with hemoglobin greater than 10 mg/dL may cause falsely elevated results with the Aspartate Aminotransferase2 assay.
  • Half life of AST is 18 hours

Test Components

AST, U/L

Measuring Range 5 - 1100 U/L

Reporting Limits 5 - 1100 U/L

Reference Ranges

AST, U/L
  Male Female
0-15 Days 32 - 162
15 Days - 1 Year 20 - 67
1-7 Years 21 - 44
7-12 Years 18 - 36
12-19 Years 14 - 35 13 - 26
>19 Years 18 - 72

Turnaround Time

STAT: 1 hour
Routine: 4 hours

Test Schedule

Daily and STAT

CPT Codes

84450

LOINC Code

30239-8

IMO Code

IMO-PROC-31001010