Liver Function Tests Flashcards
What is AST?
Aspartate aminotransferase
Where is AST normally found?
- Liver
- Heart
- Kidneys
- Skeletal muscle
- Red blood cells
At what level would AST normally be found in the blood?
Low levels
How long would AST levels take to become elevated and how long would the levels remain high?
It takes 6-10 hours for them to rise
They stay this way for 4 hours
What may cause raised AST levels?
10-20 times normal - MI, alcoholic cirrhosis
20 times normal - viral hepatitis, autoimmune hepatitis, drugs
What is ALT?
Alanine aminotransferase
Where is ALT normally found?
Mostly in the liver
(also kidneys and heart)
How do ALT levels vary between adults anch children?
Children normally have levels twice as high as adults
ALT levels vary throughout the day
True or false?
True
High levels of ALT in the blood are specific for what?
Liver damage
Levels 50 times higher than normal for ALT are indicative of what?
Viral or drug hepatitis
What is ALP?
Alkaline phosphotase
Where is ALP normally found?
- In hepatocytes lining the hepatic duct
- Bone
- Intestines
- Placenta
When with ALP levels be high?
When there is a raised bone turnover rate, such as during adolescence, during fractures, in the 3rd trimester of pregnancy and if bony metastases is present
It is also associated with liver disease
In terms of the liver, what may high levels of ALP signify?
A blockage in the bile duct
Where does bilirubin originate?
It is a breakdown product from red lood cells
What are the two forms of bilirubin?
Conjugated - created in the liver and excreted in urine (water soluble)
Unconjugated - binds to albumin
How are unconjugated bilirubin levels calculated?
By subtracting conjugated bilirubin levels from total bilirubin levels
What does high unconjugated bilirubin levels signify?
Breakdown of red blood cells is higher than the liver’s ability to process the breakdown products (unconjugated bilirubin)
When are high unconjugated bilirubin levels seen?
- Haemolysis
- Sickle cell anaemia
- Gilbert’s disease
What do high levels of conjugated bilirubin suggest?
The flow of bilirub has been disrupted and there may be an intrahepatic or extrahepatic cause or the patient may have chronic liver disease
What is albumin and where is it made?
A protein made in the liver
In liver disruption, what happens to albumin levels?
They decrease
Why are albumin levels a poor test for liver function in acute disease?
Albumin has a half life of 20 days so decreased function is not immediately evident
What is INR?
International normalised ratio
Involves at prothromin test
How does INR change in liver disruption?
It increases
(clotting factors are not produced as efficiently)
What is GGT?
Gamma-glutamyl transpeptidase
Where is GGT found mostly?
Kidneys, liver, pancreatic cells
When may GGT levels be raised?
- Obstructive jaundice
- Cholecystitis
- Alcohol abuse
How is GGT useful in interpreting the ALP result?
GGT can help determine if an ALP rise is due to problems with the liver or something else
Which tests are defined as true liver function tests?
- Bilirubin
- Albumin
- Prothrombin time (INR)
Which tests are not true liver function tests, but can still aid in determining liver function?
- ALT/AST
- ALP
- GGT
- Bilirubin
