Liver Function Tests Flashcards
What are the 8 liver functions tests that can be ordered?
Must order 6 or more of the following tests:
- Protein
- Albumin
- Plasma Bilirubin - unconjugated and conjugation
- Plasma transferases: ALT (alanine aminotransferase) and AST (aspartate aminotransferase)
- Plasma alkaline phosphatase (ALP)
- Gamma-glutamyl transferase (GGT)
- LD (lactate dehydrogenase)
What is the difference between conjugated and unconjugated bilirubin?
Unconjugated - from RBCs b’down
Conjugated - after metabolism in the liver
Where are the different enzymes located in a hepatocyte?
Cytoplasm: ALT, AST, LD
Membrane: ALP, GGT
Mitochondria: AST
What enzymes are associated with hepatocellular damage?
ALT, AST, LD (cytoplasmic)
Cause: virus, toxin (NSAIDs), anoxia
NB: AST is especially related to toxins
What enzymes are associated with biliary disease?
ALP, GGT (biliary membrane)
Cause: gallstones, cancer of biliary tree (inc gallbladder, tree, pancreas)
What increases enzymes in the cell (enzyme induction)?
Alcohol and anticonvulsants
increase GGT and ALP in the cell
ALT:
- Function
- Location
- Half life (how long does it stay in the blood)
Function: ALT (alanine transaminase) is the enzyme part of gluconeogenesis
Location:
*only cytoplasmic
*liver»_space;»> muscle, kidney
therefore considered ‘L’iver specific
Half life: 36 hours
= indicator of hepatocellular damage
= specific to liver
= raised in obesity, fatty liver, metabolic syndrome
AST
- Function
- Location
- Half life (how long does it stay in the blood)
Function: AST is an enzyme that is a part of the Kreb’s cycle
Location
- both cytoplasmic and mitochondrial
- liver, muscle, blood cells (as needed in mitochondria)
Half life: 18 hours
= indicator of hepatocellular damage
AST
- Function
- Location
- Half life (how long does it stay in the blood)
Function: AST is an enzyme that is a part of the Kreb’s cycle
Location
- both cytoplasmic and mitochondrial
- liver, muscle, blood cells (as needed in mitochondria)
Half life: 18 hours
What does AST > ALT indicate?
- Indicates that it is acute and affects the mitochondria
- Usually EtOH, toxin
What does ALT > AST indicate?
- Indicates that it is chronic (not as severe), resolving
- Usually hepatitis (still can be drugs, viral, metabolic e.g. hypoxia)
Why is the half life of ALT and AST important?
ALT half life 36 hrs; AST half life 18 hrs
In early stages, more AST is released (as baseline concentration is higher). Therefore in first 18hr - AST > ALT (acute indicator)
In later stages ( >18h), ALT has the longer half life therefore appears higher than AST (chronic indicator)
i.e. in chronic diseases, AST can seem normal, but ALT elevated
What are the common viral diseases that affect the liver (hepatitis)?
Acute: HAV, HEV - presents with high levels of ALT
Chronic: HBV (and HDV), HCV - presents with low levels of ALT
Other that cause hepatitis: EBV CMV Q Fever Rubella
What are the common drugs and toxins that cause hepatocyte damage?
Basically any drug can but most common are: - ABx: flucloxacillin, amoxil Statins: atorvastatin, simvistatin, etc - Ethanol - Paracetamol - Herbal tea (kombucha)
What are the common drugs and toxins that cause hepatocyte damage?
Basically any drug can but most common are: - ABx: flucloxacillin, amoxil Statins: atorvastatin, simvistatin, etc - Ethanol - Paracetamol - Herbal tea (kombucha)
