Liver blood test results can help health-care professionals diagnose liver disease and monitor response to treatment. The test is done on blood that is taken from a vein and is sometimes referred to as a liver panel or liver function test. A number of proteins and enzymes can be measured to get a good picture of what is happening in the liver.
The liver is a vital organ in the body, fulfilling many functions. These include storage of glycogen, metabolism of drugs, and production of some proteins necessary for clotting. It is also involved in the digestive process by producing bile that is needed to break down some fats and proteins. The liver also breaks down and excretes toxins. Liver blood test results can help diagnose if there are problems in the liver and where they are.
Liver blood test results usually include values for six different enzymes, proteins or chemicals, but some labs include an additional three on the liver panel. These are not always necessary, depending on the suspected condition, and may be ordered only after the initial screening. The same blood sample can be used to obtain all the liver blood test results.
Alanine transaminase (ALT) is an enzyme that is found largely in the liver. A raised ALT may indicate liver damage such as viral hepatitis or drug-induced hepatitis. Raised levels of alkaline phosphatase (ALP), also an enzyme found mainly in the liver close to the bile ducts, may indicate blocked bile ducts.
While raised levels of aspartate aminotransferase (AST) may point to liver problems, it is made by various other tissues, including the heart when damaged, so it is less specific than the ALT. Albumin is a protein produced by the liver so measuring this gives an indication of whether the liver is functioning optimally or not. Total protein is a measure of all the proteins produced by the liver, including albumin.
Bilirubin is a chemical that gives the bile its yellow color and is responsible for the yellow tinge to the skin and eyes that comes with jaundice. It is divided into conjugated and unconjugated bilirubin, and raised levels of these may indicate different things. If unconjugated bilirubin is high, it may indicate that red blood cells are being broken down too much, such as in hemolytic anemia. Raised conjugated bilirubin may indicate a blockage in the liver or a pancreatic tumor. Excessive drinking may also cause this.
The other three liver blood test results, namely gamma-glutamyl transferase (GGT), lactic acid dehydrogenase (LDH) and prothrombin time (PT) may be used to diagnose conditions more specifically. GGT is often raised in heavy drinkers and is quite specific to the liver. Prothrombin time measures the clotting time of the blood. Because the liver is involved in the production of many of the clotting factors, measuring PT may help to diagnose potential problems in the liver.
