What are some of the most common liver tests?
A series of special blood tests can often determine whether or not the liver is inflamed, injured, or functioning properly. These tests can also distinguish between acute and chronic liver disorders and between hepatitis (infection or inflammation of the liver) and cholestasis (disruption in the formation of or obstruction in the flow of bile).
The most commonly performed blood tests include the following:
Function tests
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Serum bilirubin test. This test measures the levels of bilirubin in the blood. Bilirubin is made by the liver and is excreted in the bile. Elevated levels of bilirubin may indicate an obstruction of bile flow or a problem in the processing of bile by the liver.
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Serum albumin test. This test is used to measure the level of albumin (a protein in the blood) and may be useful in the diagnosis of liver disease. Low levels of albumin may indicate the liver is not functioning properly.
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International normalized ratio (INR), formally called prothrombin time (PT) test. This test measures how long it takes for blood to clot. Blood clotting needs vitamin K and a protein that is made by the liver. Prolonged clotting may indicate liver disease or other deficiencies in specific clotting factors.
Liver enzymes
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Serum alkaline phosphatase test. This test is used to measure the level of alkaline phosphatase (an enzyme) in the blood. Alkaline phosphatase is found in many tissues, with the highest concentrations in the liver, biliary tract, and bone. This test may be performed to assess liver functioning and to find liver lesions that may cause biliary obstruction, such as tumors or abscesses.
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Alanine transaminase (ALT) test. This test measures the level of alanine aminotransferase. This is an enzyme found mostly in the liver that is released into the bloodstream after acute liver cell damage. This test may be performed to assess liver function, and/or to evaluate treatment of acute liver disease, such as hepatitis.
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Aspartate transaminase (AST) test. This test measures the level of aspartate transaminase. This is an enzyme that is found in the liver, kidneys, pancreas, heart, skeletal muscle, and red blood cells that is released into the bloodstream after liver or heart problems. This enzyme is released into the bloodstream after acute liver cell damage.
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Gamma-glutamyl transpeptidase test. This test measures the level of gamma-glutamyl transpeptidase. This is an enzyme that is made in the liver, pancreas, and biliary tract. This test is often performed to assess liver function, to provide information about liver diseases, and to detect alcohol ingestion.
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Lactic dehydrogenase test. This test can find tissue damage and may assist in the diagnosis of liver disease. Lactic dehydrogenase is a type of protein (also called an isoenzyme). It is involved in the body's metabolic process. However, this is a very nonspecific liver test. It is rarely used for liver disease assessment.
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5'-nucleotidase test. This test measures the levels of 5'- nucleotidase (an enzyme specific to the liver). The 5'- nucleotidase level is elevated in persons with liver diseases, especially those diseases associated with cholestasis. This is disruption in the formation of, or obstruction in the flow of bile.
Additional diagnostic tests
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Alpha-fetoprotein test. Alpha-fetoprotein (a specific blood protein) is made by fetal tissue and by tumors. This test may be done to predict the risk for primary liver cancer (hepatocellular carcinoma). It is also done to monitor the effectiveness of therapy in certain cancers, such as hepatomas (a type of liver cancer).
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Mitochondrial antibodies test. The presence of these antibodies can indicate primary biliary cirrhosis, chronic active hepatitis, and certain other autoimmune disorders.
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Serum alpha-1 antitrypsin test (A1AT). This test measures the levels of alpha-1 antitrypsin in the blood. This test is performed to help identify a rare form of emphysema in adults and a rare form of liver disease (cirrhosis) in children and adults.
