The liver performs some of the important functions of the body including the production of bile juice, storing sugars, vitamins, and minerals, regulating blood clotting and purifying the blood from harmful substances including drugs or alcohol. Certain enzymes produced by the liver help in the breakdown of proteins into energy. These enzymes are:
- Alanine Transaminase (ALT)
- Aspartate Transaminase (AST)
- Alkaline Phosphatase (ALP)
- Gamma-Glutamyl transferase (GGT)
Certain liver diseases or disorders cause the abnormal release of the above enzymes in the blood. A liver blood test or liver function test is used to investigate the elevated release of enzymes, proteins or bile juice in the blood.
Indications for a Liver Blood Test
A liver blood test is indicated for:
- Hepatitis B and C
- Liver cirrhosis
- Gallbladder disease
- Fatty liver disease
- Monitoring certain medications
- Autoimmune or toxic hepatitis
- Liver cancer
- Wilson’s disease
- Liver infection
Preparation for Liver Blood Test
Talk to your doctor regarding the medications you should avoid a few days before the test. Drink plenty of water on the day prior to the test. Any special instructions will be provided by your doctor.
Procedure for a Liver Blood Test
- A tourniquet is wrapped above your elbow by your phlebotomist (a person specifically trained to collect blood).
- The pressure causes an increased volume of blood in the veins.
- The site of injection is cleaned by an antiseptic.
- A sterilised needle is inserted to collect the amount of blood required for the test.
- The blood is collected and stored in glass vials.
- A cotton ball is pressed at the site of injection after the needle is withdrawn.
- The sample is tested for elevated liver enzymes.
Results of a Liver Blood Test
Elevated ALT and AST: Indicates damage to liver tissue due to liver infection (hepatitis B and C), liver cirrhosis, fatty liver disease, and alcohol-related disease.
Elevated ALP and GGT: Indicates obstructive liver disease, fatty liver disease, and excess alcohol intake.