Liver function tests

Question 1

State the liver function tests

Answer 1

• ALT,AST
• ALP, GGT
• Serum Bilirubin
• PT
• ALbumin
• INR

The term “liver function tests“ is a misnomer as many of the tests do not comment on the function of the liver but rather pinpoint the source of the damage.

The actual function of the liver can be graded based on its ability to produce albumin as well as vitamin K dependent clotting factors.

Question 2

What are the aminotransferases. State their physiological function and what they measure in LFT

Answer 2

• AST and ALT
• participate in gluconeogenesis by catlyzing
• AST Found in liver, cardiac and skeletal muscle, kidneys , brain, pancreas, lungs and red cells
  
  • Not sensitive or specific for liver
• ALT is a cytosolic enzyme found in high concentrations in the liver
• Elevated AST/ALT is a sign of hepatocellular injury is the trigger for release of these enzymes into circulation

Question 3

State the physiological functions of GGT and alkaline phosphatase and their role in LFT

Answer 3

ALP:

• high concentrated in microvilli of the bile canaliculus (also found in bones and intestines
• often raised in response to cholestasis -
• Glycoprotein gamma-glutamyltransferse
  
  • boring ass metabolic enzyme
  • raised in response to biliary epithelial damage and bile flow obstruction.
  • mild increases in GGT are common
  • Often runs in parallel with ALP

Both predominantly in bile ducts.

Raised ALP and GGT raised more times than it’s upper limit of normal (ULN) than AST/ALT suggests cholestatic biliary pathology.

Question 4

The ALT:AST ratio is a useful clinical indicator:

Comparefor; viral hepatitis, cirrhoris, alcoholic liver disease

Answer 4

Viral hepatitis:

• AST is higher than ALT unless
  
  • ​ cirhossis is present in which case ALT is higher than AST
  • AST:ALT ratio of more than one in viral hepatitis suggests cirrhosis

Alcoholic liver disease and steatohepatitis

• AST is higher than ALT

In patients with liver disease without cirrhosis, in whom AST is greater than ALT, alcohocl or obestity is most likely agent. AST to ALT ratio of 2:1 or greater is suggestive of alcoholic liver disease, particularly in the setting of an elevated gamma-glutamyl transferase

When ALT and AST are raised more times their ULN than ALP, this is characteristic of hepatocellular injury.

Question 5

A markedly raised ALT and GGT is highly suggestive of

Answer 5

Cholestasis

Question 7

Albumin is synthesized in the liver; therefore reduction in production suggests

Answer 7

Abnormality in liver function.

Question 8

??? and ??? produced predominantly by the bile ducts; and ???? and ????, produced predominantly by hepatocytes. Liver enzymes are a poor reflector of liver function, but rather of cholestasis and liver cell integrity, respectively

Answer 8

• ALP and GGT
• AST and ALT

Question 9

Why is INR important in looking at the liver?

Answer 9

• Test used to measure how quickly your blood clots
• If there is serious liver disease and cirrhosis, the liver may not be able to produce the proper amount of proteins and then the blood does not clot as it should.

Question 10

Aside from the clotting factors, what other explanation could be given for the the poor clotting function?

Answer 10

• Splenamegoly - for some reason when the bigger the spleen, the more platelets it sequesters.

Question 11

Elevated GGT can be a sign of what?

Answer 11

Chronic alcohol use

Question 12

If ALP is increased, but NOT GGT, then possible cause is:

Answer 12

Bone Disease