Liver function tests Flashcards
give 3 examples of enzymes which are shown up in a liver function test?
1) serum transaminase (ALT,AST)
2) alkalin phosphatase
3) gamma gluaamyl transpeptidase
what are 3 indicators of intrinsic synthetic function?
1) albumin
2) prothrombin time/INR
3) billirubin
what are transaminases?
give 3 examples of transaminases.
= hepatic enzymes that are usually intra-cellular, but are released from hepatocytes in context of hepato-cellular injury
1) catalyse gamma-amino group transferase
e. g. aspirate or alanine > keto-gluterate
2) alanine amino-transferase (ALT)
- sensitive
- cytosol located
- predominantly liver
- short half life 47hrs
3) aspirate amino-transferase (AST)
- cytosol & mitochondria
- present in liver, heart, pan, skeletal muscle, brain, liver, lungs, RBCs, WBD
- half lie 17hrs
what are amino-transferases?
what are the levels of Amin-transferases in obstructive jaundice?
- often deranged in all aetiologies
- marked increase in hepato-cellular pathologies
- levels may not reflect extent of damage
- don’t correlate with outcomes
less than 500I/L in obstructive jaunted
- except acute phase of biliary obstruction with passage of stones into CBD
= ALT values >1-2000U/L
what are alkaline phosphatase?
describe alkaline phosphatase half life.
describe the origin of alkaline phosphates.
= enzymes that catalyse the hydrolysis of a number of organic phosphate esters
= 1week
- biliary (epithelial cells of ducts) cholestasis enhances synthesis and release of ALP
- bone
- placenta
- intestine
- kidney
what is bilirubin?
= breakdown product of haem;
- transported to liver bound to albumin
- taken up in hepatocytes
- undergoes conjugation
- excreted via urine/faeces
Isolated hyperbillirubinaemia;
= conjugated v unconjugated
what is liver responsible for?
= synthesis of most clotting factors;
Factor I (fibrinogen)
Factor II (prothrombin)
V, VII, IX, X, XII, XIII
what does prothrombin time measure?
conversion time from PT > thrombin and therefore reflects vital component of liver
what does elevate PT reflect?
what are 4 other causes of prolongation?
reduce synthetic functionality
- drugs (e.g. warfarin)
- bile malabsorption causing Vit K deficiency
- consumptive coagulopathies
- congenital coagulopathy
what 7 specific things should you ask about in a history?
1) exposure to chemicals or medication
2) accompanying symptoms;
- jaundice, weight less, exanthema, fever, anorexia, pruritus, arthralgia
3) parenteral exposure;
- IV, medications/blood transfusions, intranasal drugs, tattoos, sexual history
4) travel history
- times and exposure risks e.g. contact with exotic zoonosis and unusual hobbies
5) alcohol exposure
6) occupational exposures
7) temporal variation
what medications are important risk factors for liver function test abnormalities?
1) anti-biotics
2) anti-depressants
3) HMG Co-A inhibitors
4) sulphonamides/silphonylureas
5) NSAIDS
6) anti-epileptics
7) anti-tuberculous medication
8) OTC
what does a raised PT/NR suggest?
What does ALP>ALT/AST and raised billi show?
what does ALT/AST > ALP and raised billi show?
- prolonged jaundice / Vit K malabsorption
- hepatocellualr dysfunction
- cholestasis
- hepatocellular injury
what specific feature of liver function test it used to show acute hepatocellular problems?
what else needs to be done when considering acute hepatocellular picture?
- AST:ALT ration (normal is 0.8>2 = suggestive of alcohol)
- acute liver screen
= HAV/HBV/HCV/HHEV/HIV - ultrasound liver to include doppler of HA/HV/PV
what are 5 possible mimic/overlap conditions and how would you exclude these?
1) coeliac disease
- tTG-IgA
- consider HLA typing DQ2/8
- gold standard D2 biopsies
= can present insidiously, which biochem reflecting NAFLD +/- IDA/malabsoption
2) muscle disorders (myositis, rhabdo)
- CK
3) adrenal insufficiency
4) anorexia nervosa
5) thyroid disorders
what are 4 possible rare entities?
1) auto-immune hepatitis: ASMA/immunoglobulins
2) Wilson’s’ disease: caeruloplasmin
3) haemochromatosis: ferritin/saturations
4) alpha1 anti-trypsin: levels inc type e.g. PiZZ
