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Liver
Aspartate aminotransferase (AST)
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An enzyme present in liver, cardiac muscle, skeletal muscle, kidney and red cells, so it is less liver-specific than ALT. The AST:ALT ratio helps to characterise liver disease.
Reference interval
| Conventional (U/L) | SI (U/L) | |
|---|---|---|
| Adults | 10–40 U/L | 10–40 U/L |
Specimen: Serum or heparinised plasma · Conventional × 1 = SI
Causes of high values
Liver disease (hepatitis, alcohol-related liver disease where AST:ALT is often above 2, cirrhosis), myocardial infarction, skeletal muscle injury and rhabdomyolysis, haemolysis, strenuous exercise.
Causes of low values
Usually not clinically significant. Low activity may be seen with pyridoxine deficiency, uraemia and chronic dialysis.
Pre-analytical and method notes
Haemolysed samples falsely raise AST because red cells are rich in the enzyme. Interpret together with ALT, creatine kinase and clinical context to separate hepatic from muscular or cardiac sources. Reference intervals vary by laboratory, method and population; use the interval printed on the report.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
- Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)
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