Liver Function Tests Flashcards
What is measured in LFTs? (5)
- Albumin (synthesised)
- Bilirubin (indicates cholestasis)
- Aminotransferase enzymes (AST, ALT)
- Gamma-glutamyltransferase (GGT)
- Alkaline phosphatase (ALP)
What does ALT stand for?
Where is it found?
Alanine aminotransferase
- present in liver, heart, skeletal muscles
- highest concentration in liver
What is the normal range for ALT?
5 - 55iu/L
How does the assay for measuring ALT work?
L-Alanine + ketoglutarate –> glutamine + pyruvate
Pyruvate + NAD+ –> lactate + NADH (lactate dehydrogenase)
Conversion to pyruvate is proportional to ALT present
Conversion to lactate gives further sensitivity to the assay
What does AST stand for?
Where is it found?
Aspartate aminotransferase
- liver and heart (less specific than ALT)
What is the normal range for AST?
5 - 43 iu/L
What conditions will cause both ALT and AST to rise?
Liver damage and inflammation Viral/acute immune hepatitis Excessive alcohol intake Liver tumour Fatty liver Heart failure
What does ALP stand for?
Where is it found?
Alkaline phosphatase
- found in liver, bone and placenta
- if patient has no bone disease/pregnancy, can indicate biliary tract problems
Can ALP be used alone to diagnosis liver disease?
No, must use separation techniques to identify ALP originating from the liver
Elevated ALP with GGT would indicate liver problems (cholestatic enzymes)
What is the normal range for ALP?
30 - 115iu/L
How does the assay for ALP work?
p-nitrophenyl phosphate –> p-nitrophenol + phosphate
Positive result: Yellow in alkaline solution
What does GGT stand for?
Gamma-glutamyltransferase
- compared to ALP to distinguish liver disease from other
How does the assay for GGT work?
L-y glutamy- + Gly-Gly-3-Carboxy-4-nitroanilide
–> Glu-Gly-Gly + 3-carboxy-4-nitroaniline
Positive result: yellow colour formed (absorbed at 405nm)
What causes ALP and GGT levels to rise?
Liver tumours Fatty liver Excessive alcohol Scarring of liver Liver inflammation from herbs/medications Gallstones
