Transaminases versus alkaline phosphatase and gamma GT
Expansion
Hepatitic pattern, with ALT and AST predominantly raised
- Over 1000: ischaemic hepatitis (“shock liver”), paracetamol overdose, acute viral hepatitis. Autoimmune hepatitis occasionally
- Moderate rise: alcohol, non-alcoholic fatty liver, drugs, chronic viral hepatitis, autoimmune, haemochromatosis, Wilson’s disease, coeliac disease
- AST to ALT ratio over 2: suggests alcoholic liver disease
- ALT above AST: suggests non-alcoholic fatty liver or viral hepatitis
- A falling ALT with a rising bilirubin and INR in acute liver failure indicates loss of hepatocyte mass, not recovery
Cholestatic pattern, with alkaline phosphatase and gamma GT predominantly raised
- Extrahepatic: gallstones, pancreatic or cholangiocarcinoma, stricture
- Intrahepatic: primary biliary cholangitis, primary sclerosing cholangitis, drugs (flucloxacillin, co-amoxiclav, steroids), infiltration, pregnancy, sepsis
Isolated raised alkaline phosphatase: check the gamma GT. If normal, the source is bone (Paget’s disease, metastases, osteomalacia, healing fracture, growth), placenta in pregnancy, or intestine.
Isolated raised gamma GT: alcohol, enzyme inducing drugs, fatty liver. It is sensitive but non-specific, and its main value is confirming that a raised alkaline phosphatase is hepatic.
True liver function is measured by albumin, prothrombin time and bilirubin, not by the enzymes, which reflect damage rather than function. A prolonged prothrombin time that does not correct with vitamin K indicates synthetic failure.