Normal & Abnormal Liver Function Tests

Question 1

Biochemical Tests of Liver Disease

Answer 1

• no easy measure of hepatic clearance or function
• no highly sensitive or specific test for underlying liver disease
• liver is a silent organ associated with often nonspecific symptoms (fatigue)
• all biochemical tests have limitations in prediction function and prognosis

Question 2

Complications of Liver Disease

Answer 2

• synthetic impairment
• cholestasis-impairment of bile flow
• decreased clearance
• portal hypertension - portal blood is shunted around the liver and not processed by the liver

Question 3

Biochemical Tests of Liver Disease

“Liver Function Tests”

Answer 3

• often biochemical measures of hepatocellular injury or impairment of bile flow
• true “function” tests are measures of clearance or synthetic function
• few clinically useful hepatic clearance tests - measuring drug clearance (like Lidocaine)

Question 4

Liver Chemistries

Answer 4

Tests which detect injury: aminotransferases & Alkaline phosphatase
Tests which measure clearance: bilirubin, ammonia
Tests of Synthetic Capacity: clotting factors made by liver, albumin, cholesterol - late complication of severe dysfunction

Question 5

Aminotransferases

Answer 5

• aspertate aminotransferase (AST)
• alanine aminotransferase (ALT)
• increase associated with cell injury or death
• AST elevation also increased with muscle injury
• ALT more specific for liver injury
• Marked elevations associated with primary hepatocellulary injury

Question 6

Alkaline Phosphatase

Answer 6

• Enzyme derived from bile ducts
• Correlates with intrahepatic & extrahepatic injury or obstruction
• Level associated with increased synthesis
• 3 important isoenzymes: Gut, Liver, Bone

Question 7

Cholylglycine

Answer 7

• serum bile salt

- correlates with the degree of cholestasis, intrahepatic or extrahepatic obstruction to bile flow

Question 8

Gamma Glutamyl Transferase (GGT)

Gamma Glutamyl Transpepidase

Answer 8

• enzyme in many tissues including biliary ductules
• increased with cholestasis, biliary obstruction
• increased w/induction by numerous chemicals (Phenytoid/Dilantin & ethanol)
• many meds & chemicals induce GGT that is limited to clinical utility
• isolated GGT elevation is often due to medications or ethanol

Question 9

Blirubin

Answer 9

• level represents a balance b/w input & hepatic removal
• imperfect measure of hepatic clearance & excretory function
• inc. w/impaired clearance by the liver
• inc. w/intrahepatic & extrahepatic obstruction

Question 10

Ammonia

Answer 10

• detoxified in liver by Urea cycle & glutamine synthetase reaction
• in chronic liver disease function & protosystemic shunts around liver
• often, but not perfect correlation w/hepatic encephalopathy

Question 11

Synthetic Function Tests

Answer 11

1. Prothrombin Time: prolonged when factors I, II, V, VII, X deficient or Vit. K deficient, correlates well with hepatic synthetic function
2. International Standardize Ration (INR)
3. Albumin: T1/2 ~20 days, hepatic synthesis, rapidly changed with acute illness, malnutrition

Question 12

Child Pugh Score

Answer 12

A is best
B in between
C is most impaired 
based on: alb, bili, ascites, enceph, PT/INR
Transplant 9-10

Question 13

Model of End-Stage Liver Disease (MELD)

Answer 13

international normalized ration (INR) - standardized measure of Prothrombin time, hepatic synthetic function

• bilirubin
• creatinine