liver function tests LFTs

Question 1

what is ALT/AST

Answer 1

serum transaminases
ie alanine aminotransferases
aspartate aminotransferases

Question 2

ALP

Answer 2

alkaline phosphatases

Question 3

GGT

Answer 3

gamma glutamyl transpepridase

Question 4

what are the indices of intrinsic synthetic function

Answer 4

albumin
prothrombin time (INR)
bilirubin

Question 5

transaminases

Answer 5

they catalyse y-amino group transfers

ie ALT/AST > ketoglutarate

Question 6

ALT characteristics

Answer 6

more sensitive than AST
predominantly cytosol located
predominantly liver
short half-life circa 47 hours

Question 7

AST characteristics

Answer 7

in cytosol and mitochondria
present in liver, heart, pancreas, skeletal muscle, brain , lungs RBCs WBCs

has a half life of about 17 hours

Question 8

aminotransferases

Answer 8

-marked increase in hepatocellular pathologies
-usually less than 500U/L in obstructive jaundice
»except acute phase of biliary obstruction with passage of stone into the CBD - this process may coincide with ALT values >1-2000 U/L

Question 9

alkaline phosphatases

Answer 9

these are enzymes that catalyse the hydrolysis of a number of organisms phosphate esters

• have a half life of about one week therefore often lag to rise and slow precipitation in resolution of pathology

Question 10

what is the origin of alkaline phosphatases

Answer 10

biliary - cholestasis enhances synthesis and release of ALP
bone 
placenta 
intestine 
kidney

Question 11

what is GGT

Answer 11

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

• not found in the bone
• used as a diagnostic marker for liver or cholestatic diseases
• useful in determining whether elevated ALP is of bone or of liver origin
• GGT is inducible
• levels of GGT can be increased with consumption of alcohol

Question 12

what is bilirubin involved in

Answer 12

the breakdown of the product of Heme

Question 13

what is the difference between conjugated and unconjugated hyperbilirubinaemia

Answer 13

conjugated bilirubin = water soluble and secreted into bile

unconjugated bilirubin = waste product of haemoglobin breakdown that is taken up by the liver

Question 14

what is prothrombin time

Answer 14

measure the conversion time from PT > thrombin and thus reflects a vital component of the liver

-an elevated PT may reflect reduced synthetic functionality

**the liver is responsible for synthesis of most clotting factors ie factor I = fibrinogen
factor II = prothrombin
factors V VII IX X XII and XIII

Question 15

what is a normal reference range

Answer 15

!!!!

Question 16

what areas should be converted in history taking

Answer 16

• use exposure to any chemical medication
• accompanying symptoms ( ie pruritus, jaundice, arthralgia, weight loss, exanthema, fever, anorexia )
• parenteral exposures ie IV medications/blood transfusions/intranasal drugs/tattoos/sexual history
• travel history inclusion of timings and exposure risks ie contact
• alcohol exposure
• occupational exposures
• temporal variation

Question 17

in relation to medication in history taking - what should be covered

Answer 17

timings !
has anything changed?
are they on :
antibiotics 
antidepressants
HMG Co A inhibitors 
statins 
sulphonamides
sulphonylureas
NSAIDS 
anti-epileptics 
anti-TBs

over the counter medications?

Question 18

When the ration of of ALT/AST > ALP BiliN/ increases - what does this signify

Answer 18

hepatocullular injury

Question 19

when ALPs are greater then ALT/AST Bili - what does this signify

Answer 19

cholestasis

Question 20

when there is an increase in PT/INR what could the cause be

Answer 20

prolonged jaundice/ vit K malabsorption

hepatocellular dysfunction