Aspartate aminotransferase (AST)

What it measures

AST is an enzyme present in liver, heart, skeletal muscle and red cells. It is ordered with ALT to detect and follow liver cell injury, and the AST/ALT ratio helps point toward the cause.

Specimen and preparation

• Specimen: Serum or lithium-heparin plasma
• Tube: Gold top
• Preparation: Haemolysis falsely raises AST because red cells contain it; avoid heavy exercise before collection.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Acute or chronic hepatitis
• Alcohol-related liver disease (AST/ALT often >2)
• Cirrhosis
• Muscle damage or rhabdomyolysis
• Myocardial infarction
• Haemolysis

Causes of low values

• Vitamin B6 deficiency
• Chronic dialysis

Method

Kinetic UV assay (IFCC, NADH oxidation)

Good to know

AST is less liver-specific than ALT; check CK when muscle injury is suspected.

Related tests