LFTs Flashcards
Which parts of LFT are used to distinguish between hepatocellular damage and cholestasis?
ALT
AST
ALP
GGT
What parts of the LFTs are used to assess livers synthetic function?
Bilirubin
Albumin
PT
What are ALT and ALP markers of?
ALT= hepatocellular injury i.e. normally found at high concentrations in the cell
ALP= indirect marker of cholestasis i.e. raises when liver increases synthesis in response to cholestasis
If ALP is raised, what test levels should also be looked at?
GGT
-raised when there is biliary epithelial damage or obstruction or due to alcohol or drugs
=increases ALP with GGT -> cholestasis
When is ALP raised in the absences of GGT?
Any pathology that increases bone breakdown due to ALP being present in bone
I.e. bone mets/vit D deficiency/ bone fractures
How can ALT and ALP level increases be used to determine whether there has been a hepatocellular injury or cholestasis?
> 10x ALT + <3x ALP= Hepatocellular
<10x ALT + >3x ALP= cholestasis
What level of bilirubin is jaundice likely to become clinically apparent?
> 60umol/L
What form of bilirubin alters the colour of urine? Why?
Conjugate= water soluble
If hyperbilirubinaemia is present, how can you differentiate between pre-hepatic, hepatic and post-hepatic causes?
Normal urine and stools= pre-hepatic causes i.e. haemolysis, impaired hepatic uptake, impaired conjugation
Dark urine + normal stools= hepatic cause
Dark urine + pale stools= post-hepatic (obstructive) cause
What is the role of albumin and what can a fall in levels indicate?
Protein which helps to maintain oncotic pressure in blood by binding to water, cations, FA and bilirubin
Liver cirrhosis= decreased production
Inflammation= acute phase response triggered where albumin production decreased
Excessive loss= protein-losing enteropathies or nephrotic syndrome
What does PT assess and what happens when there is liver disease/dysfunction?
Bloods coagulation tendency via extrinsic pathway
Increases PT due to decreased synthesis of clotting factors
What does the ratio of AST/ALT indicate?
Indicates whether LFTs derranged due to chronic liver disease or if it is cirrhosis + acute alcoholic hepatitis
ALT>AST= CLD
AST>ALT= cirrhosis and Acute alcoholic hepatitis
What would be the LFTs in acute hepatocellular damage? What causes acute hepatocellular damage?
ALT ++
ALP + or normal
GGT + or normal
Bilirubin + or ++
Poisoning
Infection (hep B/A)
Liver ischaemia
What would be the LFTs in chronic hepatocellular damage? What causes chronic hepatocellular damage?
ALT normal or +
ALP normal or +
GGT normal or +
Bilirubin normal or +
ALD
NAFLD
Chronic infection
Primary biliary cirrhosis
What would be the LFTs in cholestasis? What causes cholestasis?
ALT normal or +
ALP ++
GGT ++
Bilirubin ++
Viral hep ALD Primary biliary cholangitis Cancer Sepsis Sickle cell
What are the different reference ranges for components of LFT?
ALT= 3-40 IU/L AST= 3-30 IU/L ALP= 30-100 umol/L GGT= 8-60 u/L Bilirubin= 3-17 umol/L Albumin= 35-50 g/L PT= 10-14 secs
What LFTs would indicate an acute hepatic picture? What are the possible causes of this?
ALT/AST >1000
ALP raised
I.e. Liver enzymes significantly raised and biliary enzymes slightly raised
Causes= LAP
Liver ischaemia i.e. shocked liver
Acute viral hepatitis
Paracetamol overdose
What LFTs would indicate a chronic hepatic picture? What would cause this?
ALT/AST > 100s (slow but consistent hepatic death)
Decreased albumin
Raised INR
Causes:
- liver cirrhosis
- acute decompensation of chronic disease
What LFTs would you see in cholestatic picture?
ALP =>1000 i.e 3x upper limit
Raised bilirubin
ALT/AST moderately raised
Raised GGT
Causes:
- biliary disease causes obstruction (PBC/PSC/gallstones)
- cancer of the head of the pancreas
What LFTs would suggest an alcoholic picture?
Raised GGT
Raised MCV i.e. macrocytic
What acute liver problem does not present with the classical acute liver LFTs?
Acute alcoholic hepatitis
I.e. ALT/AST in 100s not 1000s
