_ Liver function tests done individually do not give the physician very much information, but used in combination with a careful history, physical examination and imaging studies, they contribute to making an accurate diagnosis of specific liver disorders. Different tests will show abnormalities in response to liver inflammation; liver injury due to drugs, alcohol, toxins or viruses; liver malfunction due to blockage of the flow of bile; and liver cancers.
An LFT, sometimes called a liver panel, is how doctors determine if liver disease is present and provides an indication of how well the liver is functioning. Once liver disease is detected, a liver panel becomes the primary diagnostic tool that doctors use to monitor disease progression. An LFT is a test for specific components in a patient's blood sample. There is generally no preparation required for this test, but you may be instructed to fast for a period of time before your blood is drawn. Some medications may impact specific measurements so ask your doctor if you take any of the meds listed for some of the tests listed below. Always following any instructions given.
1) Enzymes: Proteins that help cells do their work. When cells are injured, enzymes can leak into the blood at higher-than-normal levels. Some common enzymes used to detect liver disease are:
Alanine Aminotransferase (ALT): An enzyme found mainly in the liver; the best test for detecting hepatitis. Normal range is 0-40
Alkaline Phosphatase (ALP): An enzyme related to the bile ducts that often increases when the bile ducts are blocked. Normal range is 25-150
Aspartate Aminotransferase (AST): An enzyme found in the liver and a few other places, particularly the heart and other muscles. Normal range is 0-40
Gamma-Glutamyl Transferase (GGT):An enzyme found mainly in the liver; very sensitive to changes in liver function. Normal range is 0 -51 Drugs that may cause increased GGT levels include alcohol, phenytoin, and phenobarbital. Drugs that may cause decreased levels include oral contraceptives.
Please see the AST/ALT Story page for more information about these 2 enzymes.
2) Bilirubin: A waste product made from old or damaged blood cells. A yellow compound that causes jaundice and dark urine when present in increased amounts. Two different tests of bilirubin are often used together:
Total Bilirubin:Measures all the bilirubin in the blood. Normal range is 0.1-1.2
Direct Bilirubin: Measures a form conjugated (combined with another compound) in the liver. Normal range is < 0.3
Drugs that may cause increased blood levels of total bilirubin include anabolic steroids, antibiotics, antimalarials, ascorbic acid, Diabinese, codeine, diuretics, epinephrine, oral contraceptives and vitamin A.
3) Protein: A main function of the liver is to make protein. Two important liver protein tests are:
Albumin: A measure of the main protein made by the liver and indicates how well the liver is making this protein. Normal range is 3.5-5.5
Total Protein: A measure of albumin and all other proteins in blood, including antibodies made to help fight off infections (antibodies are not made in the liver):Normal range is 1.5-4.5