ALT is more liver specific than AST because ALT rarely increases in lesions other than the liver parenchyma. 2 types cAST 20% and mAST 80%
They are sensitive and increased even before the clinical symptoms and signs (1 week before jaundice)
Extent of increase of AST and ALT reflects the degree of hepatocellular damage
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**ALT (48h) mainly cytoplasmic elevations persist longer than do AST (18h) ? For about 5 weeks
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Persistent increase of enzymes for more than 6 months = chronic liver disease
Causes of elevated levels of blood ALT & AST: De Ritis ratio (AST/ALT ratio)
1- Viral , toxic or alcoholic hepatitis (Acute liver diseases) ***Marked increase in ALT & AST ***
- (Up to 20 - 50 - may reach up to 100 folds).
- In viral hepatitis, ALT is much elevated than AST
2- Cirrhosis (chronic liver diseases) with low prothrombin and albumin
- (Moderate increase (up to 4 – 5 folds)
- In chronic cases, AST is much elevated than ALT.
3- Obstructive jaundice (Obstructive liver diseases):
with very high ALP and (GGT)
- ALT & AST are increased up to 3 folds (moderate increase)
4- After alcoholic or drug intake: *(transient slight to moderate increase).