Expansion
Transaminases indicate hepatocellular injury; ALP and GGT indicate cholestasis
Expansion
Hepatocellular pattern (transaminases raised disproportionately)
- ALT is more liver specific than AST
- AST:ALT above 2 suggests alcoholic liver disease; below 1 suggests viral or non-alcoholic fatty liver disease
- Values above 1000 suggest viral hepatitis, ischaemic hepatitis or paracetamol toxicity
Cholestatic pattern (ALP and GGT raised disproportionately)
- Biliary obstruction, primary biliary cholangitis, drugs, infiltration
Distinguishing the source of a raised ALP: it is also produced by bone, placenta and intestine. A concurrently raised GGT confirms a hepatobiliary origin; a normal GGT points to bone (Paget disease, osteomalacia, metastases, growth in children) or pregnancy.
True function, as opposed to injury, is measured by:
- Albumin: long half-life, so it reflects chronic function
- Prothrombin time: short half-life factors, so it is the best acute marker
- Bilirubin
An important caution: transaminase levels do not indicate severity. In fulminant hepatic failure they may fall as hepatocytes are destroyed, while the prothrombin time and encephalopathy worsen.