LFTs

Question 1

Which parts of LFT are used to distinguish between hepatocellular damage and cholestasis?

Answer 1

ALT
AST
ALP
GGT

Question 2

What parts of the LFTs are used to assess livers synthetic function?

Answer 2

Bilirubin
Albumin
PT

Question 3

What are ALT and ALP markers of?

Answer 3

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

Question 4

If ALP is raised, what test levels should also be looked at?

Answer 4

GGT
-raised when there is biliary epithelial damage or obstruction or due to alcohol or drugs
=increases ALP with GGT -> cholestasis

Question 5

When is ALP raised in the absences of GGT?

Answer 5

Any pathology that increases bone breakdown due to ALP being present in bone

I.e. bone mets/vit D deficiency/ bone fractures

Question 6

How can ALT and ALP level increases be used to determine whether there has been a hepatocellular injury or cholestasis?

Answer 6

> 10x ALT + <3x ALP= Hepatocellular

<10x ALT + >3x ALP= cholestasis

Question 7

What level of bilirubin is jaundice likely to become clinically apparent?

Answer 7

> 60umol/L

Question 8

What form of bilirubin alters the colour of urine? Why?

Answer 8

Conjugate= water soluble

Question 9

If hyperbilirubinaemia is present, how can you differentiate between pre-hepatic, hepatic and post-hepatic causes?

Answer 9

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

Question 10

What is the role of albumin and what can a fall in levels indicate?

Answer 10

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

Question 11

What does PT assess and what happens when there is liver disease/dysfunction?

Answer 11

Bloods coagulation tendency via extrinsic pathway

Increases PT due to decreased synthesis of clotting factors

Question 12

What does the ratio of AST/ALT indicate?

Answer 12

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

Question 13

What would be the LFTs in acute hepatocellular damage? What causes acute hepatocellular damage?

Answer 13

ALT ++
ALP + or normal
GGT + or normal
Bilirubin + or ++

Poisoning
Infection (hep B/A)
Liver ischaemia

Question 14

What would be the LFTs in chronic hepatocellular damage? What causes chronic hepatocellular damage?

Answer 14

ALT normal or +
ALP normal or +
GGT normal or +
Bilirubin normal or +

ALD
NAFLD
Chronic infection
Primary biliary cirrhosis

Question 15

What would be the LFTs in cholestasis? What causes cholestasis?

Answer 15

ALT normal or +
ALP ++
GGT ++
Bilirubin ++

Viral hep 
ALD
Primary biliary cholangitis 
Cancer 
Sepsis 
Sickle cell

Question 16

What are the different reference ranges for components of LFT?

Answer 16

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

Question 17

What LFTs would indicate an acute hepatic picture? What are the possible causes of this?

Answer 17

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

Question 18

What LFTs would indicate a chronic hepatic picture? What would cause this?

Answer 18

ALT/AST > 100s (slow but consistent hepatic death)
Decreased albumin
Raised INR

Causes:

• liver cirrhosis
• acute decompensation of chronic disease

Question 19

What LFTs would you see in cholestatic picture?

Answer 19

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

Question 20

What LFTs would suggest an alcoholic picture?

Answer 20

Raised GGT

Raised MCV i.e. macrocytic

Question 21

What acute liver problem does not present with the classical acute liver LFTs?

Answer 21

Acute alcoholic hepatitis

I.e. ALT/AST in 100s not 1000s