Tests Flashcards
1
Q
Are hepatic enzymes usually intracellular or extracellular?
A
Intracellular
2
Q
Describe alanine aminotransferase
A
- more sensitive than AST
- predominantly cytosol-located
- predominantly liver
- short half-life circa 47 hrs
3
Q
Describe aspartate aminotransferase
A
- in cytosol and mitochondria
- present in liver, heart, pancreas, skeletal muscle, brain, lungs, RBCs, WBCs
- half life circa 17hrs
4
Q
Describe the use of aminotransferases
A
- often become deranged in all aetiologies
- marked increase in hepatocellular pathologies
- levels may or may not reflect extent of damage
- DO NOT correlate with outcomes
- usually less than 500 U/L in obstructive jaundice
- except acute phase of biliary obstruction with passage of ston into the BCD, this process may coincide with ALT values >1-2,000 U/L
- this is often a very transient phenomenon and indices revert back to that of more cholestatic picture
5
Q
Describe alkaline phosphatase
A
- enzyme that catalyses the hydrolyses of a number of organic phosphate esters
- half life around 1 week therefore often lag to rise and slow precipitation in resolution of pathology
- origin; biliary (epithelial cells of ducts) cholestasis enhances synthesis and release of ALP, bone, placenta, intestine (blood groups BandO particularly following fatty meals), kidney
6
Q
Describe bilirubin
A
- predominantly a breakdown product of heme
- transported to liver bound to albumin
- uptake into the hepatocytes
- undergoes conjugation
- excreted via urine / faeces (urobilinogen / stercobilinogen)
- isolated hyperbilirubinaemia, conjugated vs unconjugated
7
Q
Prothrombin time measures what?
A
- measure the conversion time from PT > thrombin
- reflects a vital component of the liver
8
Q
Elevated PT may reflect what?
A
Reduced synthetic functionality
9
Q
Name other causes of PT prolongation
A
- drugs (inc warfarin)
- bile malabsorption causing relative vit K deficiency
- consumptive coagulopathies
- congenital coagulopathy
