Three tests are often used to detect liver disease by measuring the levels of enzymes, bilirubin and protein present in the blood. Common tests include:

Enzymes: Proteins which help cells do their work. If cells are injured enzymes are present in the blood at higher levels than normal.

• Alanine aminotransferase (ALT): Found mainly in the liver and useful for detecting hepatitis. 
• Alkaline phosphatase (ALK Phos): This enzyme is produced in the bile ducts, intestine, kidneys, placenta and bones and is often increased with bile duct disease or bone disorders.
• Aspartate aminotransferase (AST): Found in a variety of tissues including the liver, heart and brain, and is released when any one of these tissues is damaged.
• Gamma glutamyl transferase (GGT): This enzyme is produced in the bile ducts and may be elevated due to any type of liver disease, or by some drugs, including alcohol.
  

Bilirubin: A by-product of the breakdown of red blood cells. It is the yellowish pigment causing jaundice and dark urine. This can be raised in different liver diseases as well as by other causes. There are two tests:

• Total bilirubin which measures all the bilirubin in the blood
• Conjugated bilirubin which measures a form made in the liver

Protein: One of the main functions of the liver is to make protein. Two important liver tests include:

• Albumin measures the main protein made by the liver and tells how well the liver is making this protein. It can be reduced due to liver damage and kidney disease. Levels drop with cirrhosis.
• Globulin measures the levels of globulins which includes antibodies. This may be raised when liver cells are injured.

These tests are often ordered together to determine the state of the liver and whether damage has occurred. These are known collectively as liver function tests or LFTs. 

Another test that provide an important indirect measure of liver function is the International Normalised Ratio (INR) which effectively measures the impact of vitamin K on the clotting tendency of blood. Liver disease can cause vitamin K deficiency.

 Further information about liver function tests and other pathology can be found here:

Lab Tests Online
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Page Created: 28.03.2014
Page Reviewed: 04.09.2015