Liver function test

Question 1

what blood tests are used to assess liver function

Answer 1

Alanine transaminase (ALT)
Aspartate aminotransferase (AST)
Alkaline phosphatase (ALP)
Gamma-Glutamyltransferase  (GGT)
Bilirubin
Albumin
Prothrombin time (PT)

Question 2

what do ALT, AST, ALP and GGT distinguish between

Answer 2

hepatocellular damage and cholestasis.

Question 3

what are bilirubin, albumin and PT are used to assess

Answer 3

the liver’s synthetic function.

Question 4

what is ALT a marker of

Answer 4

Hepatocellular injury. It is found in high concentrations within hepatocytes and enters the blood following hepatocellular injury.

Question 5

what is ALP an indirect marker of

Answer 5

cholestasis. It is concentrated in the liver, bile duct and bone tissues. ALP is often raised in liver pathology due to increased synthesis in response to cholestasis.

Question 6

what does raised ALP and raised GGT indicate

Answer 6

highly suggestive of cholestasis

Question 7

what does raised GGT suggest

Answer 7

biliary epithelial damage and bile flow obstruction. It can also be raised in response to alcohol and drugs such as phenytoin

Question 8

what does raised ALP in the absence of raised GGT suggest

Answer 8

non hepatobiliary pathology

Question 9

causes of an isolated rise in ALP

Answer 9

Bony metastases / primary bone tumours (e.g. sarcoma)
Vitamin D deficiency
Recent bone fractures
Renal osteodystrophy

Question 10

what if pt is jaundiced (high bilirubin) but ALT and ALP are normal

Answer 10

An isolated rise in bilirubin is suggestive of a pre-hepatic cause of jaundice.
Causes include:
Gilbert’s syndrome (most common cause)
Haemolysis (check blood film, full blood count, reticulocyte count, haptoglobin and LDH levels to confirm)

Question 11

cause of jaundice with normal urine and normal stools

Answer 11

pre hepatic jaundice

Question 12

cause of jaundice with dark urine and normal stools

Answer 12

hepatic jaundice

Question 13

cause of jaundice with dark urine and pale stools

Answer 13

post hepatic jaundice

Question 14

causes of unconjugated hyperbilirubinaemia (pre hepatic)

Answer 14

Haemolysis (e.g. haemolytic anaemia)
Impaired hepatic uptake (drugs, congestive cardiac failure)
Impaired conjugation (Gilbert’s syndrome)

Question 15

Causes of conjugated hyperbilirubinaemia (hepatic)

Answer 15

Hepatocellular injury

Cholestasis

Question 16

what causes Albumin levels to fall

Answer 16

Liver disease –> decreased production of albumin (e.g. cirrhosis).
Inflammation triggering an acute phase response which temporarily decreases albumin production
Excessive loss of albumin due to protein-losing enteropathies or nephrotic syndrome

Question 17

what does ALT>AST indicate

Answer 17

chronic liver disease

Question 18

what does AST > ALT indicate

Answer 18

cirrhosis and acute alcoholic hepatitis

Question 19

cholestasis LFT pattern

Answer 19

raised ALP, raised GGT and raised bilirubin

Question 20

chronic hepatocellular damage

Answer 20

normal/raised ALT, ALP, GGT and biliruin

Question 21

acute hepatocellular damage

Answer 21

raised ALT and bilirubin

normal/raised ALP and GGT

Question 22

causes of acute hepatocellular injury

Answer 22

Poisoning (paracetamol overdose)
Infection (Hepatitis A and B)
Liver ischaemia

Question 23

common causes of chronic hepatocellular injury

Answer 23

Alcoholic fatty liver disease
Non-alcoholic fatty liver disease
Chronic infection (Hepatitis B or C)
Primary biliary cirrhosis

Question 24

cause of isolated raised bilirubin

Answer 24

gilberts syndrome