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)
Markedly high values of aminotransferase (> 500 IU/L) usually result from?
- Acute viral hepatitis
- Toxin- or drug-induced hepatitis
- Ischemic hepatitis or hepatic infarction
Markedly high values of aminotransferase (>500 IU/L) may also result from what besides acute viral hepatitis,toxin- or drug-induced hepatitis, ischemic hepatitis or hepatic infarction? (looking for 5 or so)
- Acute exacerbation of autoimmune hepatitis
- Reactivation of chronic hepatitis B
- Acute Budd-Chiari syndrome
- Acute fatty liver of pregnancy
- Passage of common duct stone
What are four liver disorders in which aminotransferases can be normal
- Hemochromatosis
- Methotrexate induced liver injury
- Chronic hepatitis C
- Nonalcoholic fatty liver disease (NAFLD)
What enzymes are released as a consequence of decreased bile flow?
–Alkaline phosphatase (ALP)
–Gamma-glutamyl-transferase (GGT)
If the GGT level is normal in a person with a high ALP, the cause of the elevated ALP is most likely?
bone disease.
Where is alkaline phosphatase located in the liver/bile duct?
How is it eliminated?
- Apical membrane of hepatocytes and bile duct cells
- Eliminated in bile
Alkaline phosphatase is very sensitive to what?
ANy changes in bile flow
What lab test is diagnostic by itself for acute hepatitis A?
IgM antibody to hepatitis A virus (anti-HAV)
What lab test is diagnostic by itself for hepatitis B?
Hepatitis B surface antigen (HBsAg)
What lab test is diagnostic by itself for hepatitis B?
