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Liver Function Tests

From Mediwikis

Requesting

LFTs (Liver Function Tests) are often requested when a patient presents to services, either to look for a cause of their illness or to identify a "baseline" to monitor the effect of toxic drugs and treatment on the liver.

As part of the LFTs you get:

  • AST
This is found inside hepatocytes, cardiac muscle, kidneys, brain, red blood cells
  • ALT
This is found inside hepatocytes
  • Alkaline Phosphatase
This is found in the biliary tree, bones, bowel, kidneys and placental tissue
  • Bilirubin
This is normally conjugated by the liver and excreted in bile
  • Albumin
The liver produces this
  • ɣGT (gamma GT)
This is an inducible enzyme that can be found in patients with e.g. alcohol abuse or those who take enzyme inducing drugs e.g. anticonvulsants

It is also important to check other areas of the liver's synthetic function by testing clotting using:

  • Prothrombin time
  • INR

Some abnormalities

LFT Abnormality Indicates Example
AST Damage to Hepatocytes Hepatitis
ALT Damage to Hepatocytes Hepatitis
Alkaline Phosphatase See Below See Below
Bilirubin Liver disease (many) Hepatitis, cholestasis, if only thing raised think Gilbert's syndrome or Haemolysis

↑ Alkaline Phosphatase indicates damage to mainly either the biliary tree (e.g. caused by gallstones, hepatic metastases) or to bones (e.g. bone metastases) so remember to look at the clinical picture when reviewing results.


The synthetic function of the liver is also reduced in liver disease, especially chronic liver disease or cirrhosis which may lead to a prolonged prothrombin time (as the lack of clotting factors normally produced by the liver means that it takes longer for clots to form) and a reduced albumin.

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