Liver Function Test
Why Do A Liver Function Test?
1. To confirm a clinical suspicion of liver injury or disease
2. To distinguish between hepatocellular injury (hepatic jaundice) and
cholestasis (post-hepatic or obstructive jaundice)
Liver Function Reference Ranges
ALT 3-40 iu/l
AST 3-30 iu/l
ALP 3-100 umol/l
GGT 8-60 u/l
Bilirubin 3-17 umol/l
Albumin 35-50 g/l
PT 10-14 seconds
ALT – found in high concentration within hepatocytes and enters the blood
following hepatocellular injury. Is a useful marker of hepatocellular injury.
ALP – concentrated in the liver, bile duct and bone tissues. ALP is often
raised in liver pathology due to increased synthesis in response to
cholestasis. It is a useful indirect marker of cholestasis.
Assess if ALT and/or ALP is raised:
o If the ALT is raised, decide if this is a more than a 10-fold rise or less
than a 10-fold rise
o If ALP is raised, decide if this is a more than 3-fold rise or less than a
3-fold rise.
Comparing ALT and ALP
>10 fold increase in ALT and <3 fold increase in ALP = predominantly
hepatocellular injury
<10 fold increase in ALT and >3 fold increase in ALP = cholestasis
It is possible to have a mixed picture involving both hepatocellular injury
and cholestasis.
Gamma GT
, If there is a rise in ALP, then GGT should be reviewed. 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 and GGT is suggestive of cholestasis.
Isolated ALP Rise
Isolated ALP in the absence of GGT should raise suspicion of non-
hepatobiliary pathology. ALP is present in bones and anything that leads
to bone breakdown can cause a rise in ALP levels.
Causes of an isolated ALP rise:
o Bony metastasis or primary bone tumours
o Vitamin D deficiency
o Recent bone fractures
o Renal osteodystrophy
Isolated Rise in Bilirubin
An isolated rise in bilirubin is suggestive of pre-hepatic jaundice. This
could be caused by:
o Gilbert’s syndrome
o Haemolysis
Check blood film, FBC, reticulocyte count, haptoglobin and
LDH levels to confirm.
Assessing Hepatic Function
The liver’s main synthetic functions are:
o Conjugation and elimination of bilirubin
o Synthesis of albumin
o Synthesis of clotting factors
o Gluconeogenesis
Investigations which assess synthetic liver function are:
o Serum bilirubin
o Serum albumin
o Prothrombin Time
o Serum blood glucose
Why Do A Liver Function Test?
1. To confirm a clinical suspicion of liver injury or disease
2. To distinguish between hepatocellular injury (hepatic jaundice) and
cholestasis (post-hepatic or obstructive jaundice)
Liver Function Reference Ranges
ALT 3-40 iu/l
AST 3-30 iu/l
ALP 3-100 umol/l
GGT 8-60 u/l
Bilirubin 3-17 umol/l
Albumin 35-50 g/l
PT 10-14 seconds
ALT – found in high concentration within hepatocytes and enters the blood
following hepatocellular injury. Is a useful marker of hepatocellular injury.
ALP – concentrated in the liver, bile duct and bone tissues. ALP is often
raised in liver pathology due to increased synthesis in response to
cholestasis. It is a useful indirect marker of cholestasis.
Assess if ALT and/or ALP is raised:
o If the ALT is raised, decide if this is a more than a 10-fold rise or less
than a 10-fold rise
o If ALP is raised, decide if this is a more than 3-fold rise or less than a
3-fold rise.
Comparing ALT and ALP
>10 fold increase in ALT and <3 fold increase in ALP = predominantly
hepatocellular injury
<10 fold increase in ALT and >3 fold increase in ALP = cholestasis
It is possible to have a mixed picture involving both hepatocellular injury
and cholestasis.
Gamma GT
, If there is a rise in ALP, then GGT should be reviewed. 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 and GGT is suggestive of cholestasis.
Isolated ALP Rise
Isolated ALP in the absence of GGT should raise suspicion of non-
hepatobiliary pathology. ALP is present in bones and anything that leads
to bone breakdown can cause a rise in ALP levels.
Causes of an isolated ALP rise:
o Bony metastasis or primary bone tumours
o Vitamin D deficiency
o Recent bone fractures
o Renal osteodystrophy
Isolated Rise in Bilirubin
An isolated rise in bilirubin is suggestive of pre-hepatic jaundice. This
could be caused by:
o Gilbert’s syndrome
o Haemolysis
Check blood film, FBC, reticulocyte count, haptoglobin and
LDH levels to confirm.
Assessing Hepatic Function
The liver’s main synthetic functions are:
o Conjugation and elimination of bilirubin
o Synthesis of albumin
o Synthesis of clotting factors
o Gluconeogenesis
Investigations which assess synthetic liver function are:
o Serum bilirubin
o Serum albumin
o Prothrombin Time
o Serum blood glucose
