ALT/AST

• 🍒Raised ALT/AST levels in the blood occur in heaptocellular injury

• 🍒An AST:ALT ratio greater than 2:1 is classical of Alcoholic liver disease

• 🍒What are the expected changes in LFTs in non-alcoholic fatty liver disease

• 🍒A greater than 10-fold increase in ALT and a less than 3-fold increase in ALP suggests a predominantly hepatocellular injury

• 🍒A less than 10-fold increase in ALT and a more than 3-fold increase in ALP suggests cholestasis

• 🍒Hepatocellular injury is suggested by what changes in ALT and ALP

• 🍒Cholestasis is suggested by what changes in ALT and ALP

https://www.racgp.org.au/getattachment/36d1c5e0-9c1d-43fc-a8a0-b323e3ed8fbe/Liver-function-tests.aspx

ALP/GGT

• ALP is derived from biliary epithelial cells and bones ⇒ marker of cholestasis or bone disease
• GGT is found in hepatocytes and also biliary epithelial cells
• Raised ALP with normal GGT ⇒ bone disease (e.g. Paget’s disease, vitamin D deficiency, bony metastases)
• Raised ALP and GGT ⇒ cholestasis
• Isolated raised GGT ⇒ alcohol excess

Bilirubin

• Waste product of haemoglobin breakdown
• Can be used as a marker of severity in an acute cholestatic pathology
• Metabolised and excreted by liver
• Raised bilirubin causes jaundice
• Raised levels of bilirubin in the blood can be caused by:
  • Excess bilirubin production (pre-hepatic jaundice) ⇒ e.g. haemolysis ⇒ raised bilirubin with normal LFTs
  • A breakdown in bilirubin metabolism (hepatocellular jaundice)
  • A blockage in the bile excretion pathway (cholestatic jaundice)

Albumin

• A non-specific marker of synthetic function
• A fall in albumin can be due to:
  • Decreased production: malnutrition, severe liver disease
  • Increased albumin loss: protein losing enteropathies, nephrotic syndrome
• Albumin has a half-life of 20 days, so it will take time to decrease, even in severe liver disease.
  • Further assessment of the synthetic function of the liver can be gained by ordering a coagulation screen, as the liver is also responsible for the synthesis of clotting factors. ⇒ increased PT and INR

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