Final answer:
ALT is an enzyme that is measured in both small and large animals to assess liver function, but it is not liver-specific as it is also found in other tissues. AST and ALP enzymes are also used to evaluate liver health, and reference ranges for these enzymes are established to assist with interpretation.
Step-by-step explanation:
Alanine transaminase (ALT) is an enzyme measured to assess liver function and is present in both small and large animals. ALT rises sharply in instances of acute liver damage, such as viral hepatitis or a paracetamol (acetaminophen) overdose, indicating liver issues. However, ALT is also found in red cells, and cardiac and skeletal muscles, which makes it not exclusive to the liver. The ratio of another enzyme, aspartate aminotransferase (AST) to ALT, helps differentiate the causes of liver damage. An enzyme that is more specific to the liver, alkaline phosphatase (ALP), increases in situations like bile duct obstruction or liver diseases. Therefore, for diagnosing liver conditions in both small and large animals, ALT is a significant enzyme to measure, though it should be interpreted alongside other tests.
Normal reference ranges for these enzymes in blood tests are:
- AST: 5-20 IU/litre
- ALT: 5-15 IU/litre
- Creatine phosphokinase (CPK): 10-60 IU/litre