LFT Review - SRS Flashcards
What are the four categories of “liver” tests?
What are the specific things tested in each case?
Hepatocellular damage: AST/ALT
Liver synthetic function: Albumin, PT/INR
Cholestasis: Alk Phos, GGT
Biliary Excretion: TBili, DBili
What is GGT?
•gamma-glutamyl transpeptidase present in the cell membranes of many tissues,
ALT is used to assess liver cell injury/death… Where is it found? Be general and specific.
General: Liver only
Specific: cytosol of hepatocytes
Where is aspartate transaminase found?
Again, be specific and general.
General: Many tissues (Liver, muscle, brain, kidney)
Specific: Both cytosol and mitochondria
What do ALT/AST do and what rxn are they important in?
Catalyze the transfer of α-amino groups from amino acids to α-keto acids. These enzymes are important in gluconeogenesis.
What are two problems with using transaminases to assess liver injury?
Only assess injury over the past 1-2 days
magnitude of elevation does not necessarily correlate with extent of liver function or dysfunction.
Ok, so if ALT/AST don’t correlate with extent of liver function/dysfunction, what exactly do they tell us?
Rate of destruction of hepatocytes
Why are AST levels higher than ALT levels in alcoholic liver disease?
2 reasons
- Deficiency in Pyridoxal 5’-phosphate (P5P) which is required for synthesis of AST and ALT. For some reason though, ALT synthesis is MORE depressed than AST synthesis. (From body section of .ppt, so probably more high yield for this exam)
- Also, ETOH is toxic to mitochondria, and AST is in mitochondria, so with ETOH toxicity, more AST is presumably released. (Taken from notes section of .ppt)
Based on the AST/ALT ratio, identify the likely causes of each of these three scenarios.
Mild increases in aminotransferase (< 300 IU/L) are nonspecific and often present in disorders such as? (give 4)
What is the most common cause of mildly increased AST/ALT?
- Nonalcoholic fatty liver disease (NAFLD)
- Cirrhosis secondary to viral hepatitis
- Cholestatic liver disorders
- Hepatocellular cancer
Most common = Fatty liver (he doesn’t specify Alcoholic or NAFLD)
Based solely on the AST/ALT levels what would you guess this is representative of?
Alcoholic hepatitis
Again, what do you see here?
Chronic hepatitis (Cirrhosis has overlap but slightly lower)
What do you see here potentially?
Cirrhosis (again, overlap with chronic hepatitis but CH would be slightly higher potentially)
How about here?
Normal
What might have caused this level of elevation?
Toxic injury or ischemia (some overlap with viral hepatitis but VH would be potentially a bit lower)
How about now?
Acute viral hepatitis (overlap with toxic/ischemic injury, but AVH tops out around 3K generally)
