Liver Function Tests

Question 1

What enzymes are tested for in a liver function test?

Answer 1

(ALT/AST) - serum transaminases
(ALP) - Alkaline Phosphatase
(GGT) - gamma glutamyl transpeptidase

Question 2

What are the substances which are indications of the intrinsic synthetic function?

Answer 2

albumin
prothrombin time/INR
bilirubin

Question 3

What are transamines?

Answer 3

Hepatic enzymes that are usually intracellular, but are released from hepatocytes in context of hepatocellular injury.

Question 4

What reaction do transamonases catalyse?

Answer 4

y-amino group transfer e.g. aspartate or alanine to ketoglutarate

Question 5

Give an example of an ALT and it’s properties

Answer 5

alanineamino transferase

• more sensitive than AST
• predominantly cytosol-located
• found mainly in the liver
• half life 47hrs

Question 6

Give an example of an AST and its properties

Answer 6

aspartate aminotransferase

• in cytosol and mitochondria
• found in Liver, Heart, Pancreas, Skeletal muscle, Brain, Lungs, RBCs, WBCs
• Half Life Circa 17hrs

Question 7

What can be learned from aminotransferase levels?

Answer 7

• deranged in most aetiologies
• increase in hepatocellular pathologies
• sometimes levels effect level of damage
• obstructive jaundice usually less than 500U/L

Question 8

What are alkaline phosphatases?

Answer 8

Enzymes that catalyzes the hydrolyses of a number of organic phosphate esters.
Half-life about 1 week; therefore often lag to rise and slow precipitation in resolution of pathology.

Question 9

What is the indication of biliary cholestasis (decrease in bile flow due to obstruction or decreased secretion)?

Answer 9

High ALP

high alkaline phophatase

Question 10

Where does alkaline phosphatase ALP originate from?

Answer 10

epithelial cells of the biliary tree ducts
bone 
placenta
intestine
kidney

Question 11

What is gamma glutamyl transpeptidase?

Answer 11

Enzyme involved in gluthionine metabolism, transfer of amino acids across cellular membranes and leukotriene metabolism

Question 12

Why are GGTs useful when compared to ALPs?

Answer 12

they help determine whether the elevated ALPs are due to bone or liver damage

Question 13

Where do GGTs originate?

Answer 13

liver
kidneys
bile duct
pancreas
gallbladder
spleen
heart
brain
seminal vesicle
Not bone.

Question 14

What is GGT used as a marker for?

Answer 14

liver or cholestatic disease

Question 15

What can induce GGT elevation?

Answer 15

drugs particularly anticonvulsants and TCAs and Paracetamol. 
Diabetes mellitus
pancreatic disease
COPD
renal disease
alcohol consumption

Question 16

What is the normal process for bilirubin?

Answer 16

Predominantly a breakdown product of Heme
Transported to liver bound to albumin
Uptake into the hepatocytes
Undergoes conjugation
Excreted via urine/faeces (Urobilinogen/Stercobilinogen)

Question 17

What are 2 forms that bilirubin can be found in in blood tests?

Answer 17

conjugated and unconjugated

Question 18

What clotting factors is the liver responsible for the synthesis of?

Answer 18

Factors 1,2,5,7,9,12,13

1 (fibrinogen) and 2 (prothrombin)

Question 19

What does the PT measure?

Answer 19

conversion time from prothrombin to thrombin

Question 20

What is elevated PT an indication of?

Answer 20

reduced synthetic functionality
can also be a result of
Drugs (inc Warfarin)
Bile malabsorption causing relative Vit K deficiency
Consumptive coagulopathies
Congenital coagulopathy

Question 21

What is one of the most important aspects of LFT history takings?

Answer 21

what has changed since the difference in measures - any and all medications

Question 22

What LFT indicates hepatocellular injury?

Answer 22

ALT/AST> ALP

raised bilirubin

Question 23

What LFT indicates cholestasis?

Answer 23

ALP>ALT/AST

raised bilirubin

Question 24

What LFT indicates Prolonged Jaundice/Vit K, Malabsorption

& Hepatocellular Dysfunction?

Answer 24

Increased PT/INR

Question 25

What is the problem with the albumin test?

Answer 25

It is a difficult measure of liver function when used in isolation

Question 26

What is the normal AST:ALT ratio?

Answer 26

0. 8, >2 suggests alcohol | - can give a picture of the hepatocellular picture

Question 27

What diseases can cause a strange AST:ALT ratio so need to be ruled out?

Answer 27

``` Coeliac Disease Muscle disorders (Myositis, Rhabdomyolysis) Creatine Kinase (CK) Adrenal Insufficiency Anorexia Nervosa Thyroid Disorders ```

Question 28

What causes an increase in unconjugated bilirubin?

Answer 28

Increased bilirubin production Impaired hepatic bilirubin uptake Impaired bilirubin conjugation

Question 29

What can cause increased bilirubin production?

Answer 29

Extra/intravascular haemolysis | Extravasation of blood into tissues

Question 30

What can cause impaired hepatic bilirubin uptake?

Answer 30

Heart Failure Portosystemic Shunts Drugs; Rifampicin, Probenecid

Question 31

What can cause impaired bilirubin conjugation?

Answer 31

Gilbert’s/CN Type II Hyperthyroidism Advanced Liver Disease

Question 32

What can cause an increase in conjugated bilirubin?

Answer 32

Extrahepatic Cholestasis (Biliary Obstruction) Intrahepatic Cholestasis Drugs

Question 33

What drugs can cause an increase in conjugated bilirubin?

Answer 33

Alkylated Steroids | Chlorpromazine, herbs, Rifampicin

Question 34

What can cause Extrahepatic Cholestasis (Biliary Obstruction)?

Answer 34

``` Cholelithiasis Primary Sclerosisng Cholangitis Cholangiocarcinoma Head of Pancreatic Tumour Acute/Chronic Pancreatitis ```

Question 35

What can cause Intrahepatic Cholestasis?

Answer 35

``` Sepsis/Hypoperfusion states Cirrhosis Infiltrative Diseases TPN Acute Hepatitis ```