The Significance of Liver Function Test Results

ALP: alkaline phosphatae:
-in a child, ALP 2x adult URL (growing bones)
-in a teenager, ALP 3x adult URL (growing bones)
-older people have increased URL (osteoporesis/osteolytic mechanisms)
-Pregnant women have higher ALP due to placental production
-in normal non-pregnant people: main sources of ALP: liver and bone
-Significance of raised ALP: can’t tell if its bone or liver, best to tie in with clinical symptoms and other tests
- Raised GGT and ALP with hyperbilirubinaemia shows biliary blockage
- In the case of liver, ALP is present in the biliary epithelium

GGT: gamma glutamyltransferase
- GGT is higher in men as prostate and testes also secretes GGT
- Raised GGT and ALP = likely cholestatic condition (i.e. GGT's function is to investigate cause of raised ALP as that of biliary or extrabiliary =)
- Raised GGT = acute or chronic alcohol toxicity
- GGT as monitoring marker for long term alcohol abstinence: a month of abstinence = GGT returns to normal. This may be complicated by other liver pathologies yielding false positives.

AST and ALT:
- ALT is more specific for liver
- AST is also found in cardiac and skeletal muscles, and RBCs
- AMI and skeletal muscle diseases may result in raised AST
- elevated LDH also shows liver damage. however LDH, if you can recall, is one of the first marker enzymes for AMI

5NT: 5' nucleotidase
- the use of 5' nucleotidase is similar to that of GGT
- they serve to investigate the cause of raised ALP as that of biliary or extrabiliary

Advanced Stuff:
Discussion of AST/ALT ratio

Scenario 1: AST/ALT ratio >2, ALT
- AST/ALT ratio >2 is characteristically seen in people with alcoholic liver disease
- this relative low ALT is due to deficiency in pyridoxine 5 phosphate (P5P)
- in addition: raised GGT, MCV and Platelet count

Scenario 2: AST/ALT ratio >2, ALT > 500IU/L
- it suggests a diagnosis other than alcoholic liver disease

Scenario 3: AST/ALT <1.o
- viral hepatitis, especially hepatitis C
- the AST/ALT ratio may subsequently rise due to cirrhotic changes