Blood test primer: The LFT

Question 1

What is the LFT?

Answer 1

Liver function test

Question 2

What is measured in an LFT panel for liver damage?

Answer 2

ALT
AST
ALP
GGT

Question 3

What is measured in an LFT for Liver function?

Answer 3

Bilirubin
Albumin
Blood clotting

Question 4

What is ALT & AST?

Answer 4

Alanine aminotransferase
Aspartate aminotransferase
enzymes released from liver cells

Question 5

What is ALP & GGT?

Answer 5

Alkaline phosphate
Gamma- glutamyl transferase
from bile duct lining cells

Question 6

What does liver cell (hepatocyte) damage release?

Answer 6

ALT
AST

Question 7

What does bile duct (cholangiocyte) damage release?

Answer 7

ALP
GGT

Question 8

What does Haem get transfered into?

Answer 8

Haem transfered by spleen into bilirubin
Old blood cells are processed by the spleen
Unconjugated bilirubin is released which enters hepatocytes via OATP1B1 in the liver where it is transfered into conjugated bilirubin by UGT1A1 enzyme. Conjugated bilirubin then released by AT into Bile Caniliculus

Question 9

What is UGT1A1?

Answer 9

Enzyme involved in conjugating bilirubin
can be mutated

Question 10

What do increases in bilirubin on blood tests show?

Answer 10

Failure in any of the steps to metabolise bilirubin

Question 11

What does decision making depend on?

Answer 11

pattern, duration & severity of abnormality

Question 12

What patterns are there for a HEPATOCELLULAR LFT?

Answer 12

ALT increased
AST increased
ALP & GGT normal/ near normal

Question 13

What pattens are there for a CHOLESTATIC OR OBSTRUCTIVE LFT?

Answer 13

ALT & AST normal
ALP & GGT increased

Question 14

What are acute causes of Hepatocellular?

Answer 14

Viral hepititis
Drugs particularly paracetamol
Ischaemia

Question 15

What are chronic causes of Hepatocellular?

Answer 15

Viral hepatitis
Drugs
Fatty liver (alcohol, overweight)
Autoimmune hepititis

Question 16

What are the acute causes of Cholestatic?

Answer 16

Pancreatic or billary cancer
Gallstone disease

Question 17

What are chronic causes of Cholestatic?

Answer 17

Gallstone disease
Primary biliary cholangitis
Primary sclerosing cholangitis
Drugs

Question 18

What else is the liver responsible for?

Answer 18

Making some clotting factors. If liver not functioning correctly INR= abnormal

Question 19

Is LFT a good measure of severity?

Answer 19

The degree of abnormality in damage markers is a poor guide to severity
Bilirubin & Albumin can take time to change following injury
INR is sensitive to liver disease

Question 20

What are the 5 critical functions of the liver?

Answer 20

• Protein synthesis
• Drug metabolism
• Glucose metabolism (converts glucose- glycogen, glyconeogenesis)
• Ammonia metabolism
• Bile formation

Question 21

What is the impact on protein synthesis following acute liver injury?

Answer 21

Failure to produce clotting proteins

Question 22

What is the impact on drug metabolism following acute liver injury?

Answer 22

Bilirubin not processed, jaundice (levels of bilirubin increase)

Question 23

What is the impact on Glucose metabolism following acute liver injury?

Answer 23

No gluconeogenesis, hypoglycaemia (blood sugar drop)

Question 23

What is the impact on Ammonia metabolism following acute liver injury?

Answer 23

Ammonia accumulates, confusion

Question 24

What happens when there are toxic doses of paracetamol?

Answer 24

Build up of NAPQI= highly toxic= liver injury
The other pathways normally used are going as fast as they can so other pathway has to be used which is highly toxic pathway

Question 25

What is the treatment for toxic paracetamol dose?

Answer 25

Glutathione, processes NAPQI into non-toxic metabolite

Question 26

Where does Glutathione come from?

Answer 26

N- acetyl cysteine

Question 27

What is the normal bilirubin value?

Answer 27

normal <19

Question 28

What is the normal ALT value

Answer 28

normal <40

Question 29

What is the normal ALP value?

Answer 29

normal<110

Question 30

What is the normal INR value?

Answer 30

normal 0.9-1.2