LFTs

Question 1

AST/A:T

Answer 1

Released after hepatocellular injury

ALT is more specific to Liver injury

AST - skeletal msucle, heart, RBCs - spread

Question 2

ALP

Answer 2

May originate from liver, or bone
(raised in growing children)

ALP is often raised in liver pathology due to increased synthesis in response to cholestasis. As a result, ALP is a useful indirect marker of cholestasis.

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

Question 3

GGT

Answer 3

Liver, pancreas, renal tubules and intestine - but not bone
—> Indicates whether raised ALP is from bone or liver

Not specific to alcohol damage to the liver

A raised GGT can be suggestive of biliary epithelial damage and bile flow obstruction. It can also be raised in response to alcohol and drugs such as phenytoin. A markedly raised ALP with a raised GGT is highly suggestive of cholestasis.

Question 4

Other tests of heaptic function

Answer 4

Serum albumin
Serum bilirubin
PT (INR)

Question 5

Alcoholic liver disease

Answer 5

AST/ALT ratio is 2:1 or more

Question 6

Acute viral hepatitis

Answer 6

ALT
Bilirubin may be normal
AST may be raised

Question 7

Cholestasis predominant liver injury

Answer 7

ALP and GGT raised

AST and ALT mildly raised

Question 8

Why test LFTs

Answer 8

Confirm clinical suspicion of potential liver injury or disease
Distinguish between hepatocellular injury (hepatic jaundice) and cholestasis (post-hepatic or obstructive jaundice)

Question 9

What blood tests assess liver function

Answer 9

ALT - hepatocellular damage
AST - hepatocellular damage
ALP - cholestasis
GGT - cholestasis
Bilirubin - reduced synthetic function
Albumin - reduced synthetic function
PT - reduced synthetic function

Question 10

What is patient is jaundiced but ALP and ALT levels are normal?

Answer 10

An isolated rise in bilirubin is suggestive of a pre-hepatic cause of jaundice.

Causes of isolated jaundice include:

Gilbert’s syndrome (most common cause)
Haemolysis (check blood film, full blood count, reticulocyte count, haptoglobin and LDH levels to confirm)

Question 11

Functions of liver

Answer 11

Conjugation and elimination of bilirubin
Synthesis of albumin
Synthesis of clotting factors
Gluconeogenesis

Question 12

AST/ALT ratio

Answer 12

ALT > AST is seen in chronic liver disease

AST > ALT is seen in cirrhosis and acute alcoholic hepatitis

Question 13

What LFT in acute hepatocellular damage? Causes?

Answer 13

Raised ALT
Normal or slightly raised ALP
Normal or slightly raised GGT
Raised bilirubin

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

Question 14

LFT in chronic hepatocellular damage? Causes?

Answer 14

Normal or slightly raised ALT
Normal or slightly raised ALP
Normal or slightly raised GGT
Normal or slightly raised bilirubin

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

alpha-1 antitrypsin deficiency
Wilson’s disease
Haemochromatosis

Question 15

LFT in cholestasis

Answer 15

Normal or slightly raised ALT
Raised ALP
Raised GGT
Raised bilirubin

Question 16

Tests in liver screen

Answer 16

LFT
Coagulation
HEaptitis serolgoy
EBV
CMV
AMA
ASMA
ANA
pANCA
A1AT
Immunoglobulins
SErum copper
Ferritin