Liver function tests are done to diagnose liver diseases. It includes the measurement of different liver enzymes, proteins, billurubin and other chemicals produced by liver. Some of the important liver function tests and why they are important are discussed in this article.
Importance of liver function tests
Liver function tests (LFT) are done to detect any infection, inflammation or damage to the liver cells. Increased levels of LFT indicate abnormality of the liver.
- Liver function tests are done to measure the level of enzymes which are raised in some liver diseases.
- Liver function tests also help to evaluate if the liver is infected by viruses such as hepatitis.
- Liver function tests help to determine the prognosis of a disease such as alcoholic hepatitis, its further management and treatment.
- Liver function tests are also done to check the side effects of recently started medication.
- Increased level of particular enzymes indicate a specific disorder. Thus LFT also helps to evaluate specific diagnosis of the disease and its treatment.
Types of Liver Function Tests
There is a group of blood tests done to determine any damage or disease of the liver. These function tests help to determine the increased or decreased levels of certain enzymes, proteins and other chemicals. Some of the important liver function tests are discussed below:-
- Alanine aninotransferase (ALT): This is an enzyme produced by the liver cells. When liver cells are inflamed or damaged due to some disease this enzyme is released into the blood serum. Elevated levels of ALT in the blood indicate the presence of some liver infection or inflammation.
- Bilirubin: Bilirubin is produced by the breakdown of aged red blood cells (RBC) in the body. It is normally excreted from the body, but when the liver is diseasedthe level of bilirubin in the blood increases, which causes yellow discoloration of the skin and conjunctiva.
- Alkaline Phosphatase: This is another enzyme associated with liver disease. It is not a specific enzyme as it is also related with kidney or intestinal damage. But, if other liver function tests are abnormal, it may also be associated with liver damage or inflammation.
- Albumin: Albumin is the major protein manufactured by the liver. It is a reliable test to diagnose liver diseases. Albumin is decreased in diseases such as cirrhosis of the liver.
- Prothrombin time (PT): Liver manufactures many proteins which help in the manufacture of Vitamin K thus helping in the clotting of the blood. Prolonged prothrombin time indicates the presence of liver disease. It is not a specific test to diagnose liver disease. It is done along with other LFT.
Liver function test are helpful in determining the extent of liver disease or damage caused by the disease. But along with these test it is also necessary to take complete physical and medical histories of the patient.
Sherwood P, Lyburn I, Brown S, et al: How are abnormal results for liver function tests dealt with in primary care? Audit of yield and impact. BMJ. 2001 Feb 3;322(7281):276-8. [abstract]
Limdi JK, Hyde GM; Evaluation of abnormal liver function tests. Postgrad Med J. 2003 Jun;79(932):307-12. [abstract]
Giannini EG, Testa R, Savarino V; Liver enzyme alteration: a guide for clinicians. CMAJ. 2005 Feb 1;172(3):367-79. [abstract]
Walsh K, Alexander G; Alcoholic liver disease. Postgrad Med J. 2000 May;76(895):280-6. [abstract]