Liver function tests

Liver function tests

1. Transaminases AST/ALT:- Reflect all cell damage

   • AST
     • High amounts found the the liver, heart and muscle cells. Not specific to the liver unless performed with other tests
     • AST can be disproportionately elevated in alcohol related liver disease
   • A drop in aminotransferase suggests a decrease in hepatocellular damage
   • ALT
     • More specific to the liver than AST
     • Also found in the heart liver and pancreas
   • Levels > 100 X URL Usually from toxic ingestion and ischemic hepatic injury
   • Marked increase > 10-100 X URL Hepatic injury with ALT>AST
   • Marked increase > 10-100 X URL Hepatic necrosis AST>ALT – poor prognosis
   • •Moderate to slight increase < 5-10 X URL Uncomplicated cholestatsis Alcoholic hepatitis

2. Alkaline phosphatase ALP

   • Protein found in all body tissues. Tissues with higher amounts of ALP include the liver, bile ducts, and bone.
   • hydrolase enzyme responsible for removing phosphate groups from many types of molecules
   • In cholestasis plasma ALP is increased due to increased enzyme synthesis
   • Cholestatsis – obstructive jaundice – greater than 300U/L
   • Hepatic injury – less than or equal to 300U/L
   • High ALP may also occur in infiltrative diseases, when space occupying lesions occur (tumors) – 200-250 U/L

3. Bilirubin

   • Product of heme metabolism
   • Bilirubin is conjugated with glucuronic acid by the enzyme glucuronyltransferase
   • Secreted into the biliary canalicli and eventually reaches the gut
   • Converted to urobiliogen through bacterial action. Oxidized to stercobilin
   • Some urobiliogen is a sorbed from the small intestine and enters entrohepatic circulation. the kidneys then filtered through the kidneys to produce urinary urobilinogen

4. GGT

   • Typically elevated in cholestasis (with elevated ALP) but, if ALP normal, suggests induction of hepatic metabolic enzymes (e.g alcohol or enzyme-inducing drugs).

5. Albumin

   • Albumin - sensitive marker of hepatic function, but not useful in the acute stages as it has a long half life (20 days)