Serum Enzymology
NSW Department of Primary Industries refers all clinical chemistry testing to a specialist laboratory. Test results are incorporated into the laboratory report which includes normal ranges supplied by the testing laboratory.
Serum enzymology is usually undertaken as part of a package of tests eg liver profile. renal profile, ruminant metabolic profile. The most frequently requested serum enzymes are:
- Aspartate aminotransferase (AST) also known as Glutamic oxaloacetic transaminase (GOT)
- Creatine kinase (CK), also known as creatine phosphokinase (CPK)
- Gamma glutamyltransferase (GGT)
- Glutamate dehydrogenase (GLDH)
Specimens required
- 10 ml of blood, clotted in vacuum tubes.
NB. If blood cannot be sent to the laboratory overnight, it should be allowed to clot and the serum poured off; it should be frozen if the delay will be greater than 24 hrs. Approximately 2ml of serum per animal should be provided. It must be free of haemolysis.
Note that the stability of these enzymes is variable, as is their half life in the blood:
| Stability in serum sample | Half life in blood after insult | |
| AST | Intermediate | Weeks |
| CK | Unstable | Days |
| GGT | Very stable | - |
| GLDH | Intermediate | Weeks |
Typical disease syndromes with elevation of serum enzymes
| Enzyme | Disease process |
| AST | Sustained necrosis of hepatic and/or muscular tissue (skeletal or cardiac) |
| CK | Sustained necrosis of muscular tissues (eg. WMD) and/or CNS (eg. PE) |
| GGT | Bile duct epithelium damage, cholestasis incl cases with biliary hyperplasia (eg. chronic fascioliasis; pyrrolizidine alkaloidosis) or acute hepatic necrosis |
| GLDH | Hepatocellular damage (rises rapidly in acute hepatic necrosis) |