Laboratory Assessment of Liver Function

Describe the laboratory assessment of liver function

Synthetic Function

Measures of synthetic function include:

• Albumin
  Main plasma protein.
  • Normal range 28-58g.L^-1
  • Half-life ~20 days
  • Important in:
    • Maintenance of plasma oncotic pressure
    • Binding
      • Calcium
      • Drugs
  • Decreased in liver dysfunction and malnutrition

• Coagulation Assays
  Clotting factors are produced by the liver. Hepatic impairment may result in reduced production and abnormality of clotting assays, although functional clotting function may be normal (as pro-coagulant proteins are affected to a similar extent).
  • INR
    Test of the extrinsic pathway.
  • APTT
    Test of intrinsic pathway.

Metabolic Function

Transaminases are released when liver parenchyma is damaged, and are used to evaluate metabolic function:

• ALT
  Normal range < 54 U.L^-1.
• AST
  Normal range < 35 U.L^-1.

Obstructive Tests

• ALP (Alkaline Phosphatase)
  Enzyme involved in dephosphorylation of many compounds. ALP is found in all cells, but particularly in the liver, bile duct, bone, kidney, and placenta.
  • Normal range is 30-120 U.L^-1
• GGT
  Enzyme found in biliary duct.
  • Normal range:
    • Males: 11-50 U.L^-1
    • Females: 7-30 U.L^-1
• Bilirubin
  Byproduct of haemoglobin metabolism. May be measured as total, or as conjugated and unconjugated bilirubin.

References

1. Diaz, A. Outline the clinical laboratory assessment of liver function. Primary SAQs.