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An Overview of the Gamma-glutamyl Transpeptidase Laboratory Test

written by: angiem1981•edited by: Diana Cooper•updated: 10/31/2009

The GGT blood test can be a great diagnostic tool; however, there are many things patients may not know about the test. Most often associated with liver damage, GGT levels can also provide physicians with other essential knowledge.

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    A GGT blood test, also known as Gamma-glutamyl transferase or Gamma-glutamyl transpeptidase, (GGTP) is a laboratory test used to screen the patient for possible liver damage and/or suspected alcohol abuse. Although the test can detect elevated levels of GGT, it is typically not successful in determining the cause. While increased levels may be an indicator of various damages to the liver, the test itself is not sufficient enough for diagnosing a liver condition. For this reason, it may be common for the physician to order multiple tests such as an ALT, AST, liver panel, and other liver associated screenings.

    GGT is an enzyme that is naturally occurring in the blood. When damage, disease, or disorder occur in the liver, GGT will automatically increase, especially if the injury affects the bile duct. However, an increase in the enzyme is possible when there is no damage to the liver. Other medical conditions may also cause this as can certain drugs or medications will increase GGT in the blood, as well as smoking, and consumption of alcohol. In addition, it is perfectly normal for some individuals to have increased levels of GGT.

    The GGT blood test can be performed quickly and efficiently by drawing blood from the vein. The patient must usually fast prior to the test, as eating can increase GGT levels. In addition, the physician will also specify what medications the patient can or can not take before the test. This can include both prescription and non prescription drugs. It is also a good idea to abstain from alcohol for at least twenty four hours before the GGT blood test.

    Normal values of GGT are anywhere from 3 to 60 IU/L or international units per liter. Those of African American descent and older women may have slightly higher values. Individuals that suffer from congestive heart failure and younger women that utilize birth control contraceptives may also have increased levels. It is important to discuss any health conditions, medications, or possible risk factors with the physician prior to the GGT blood test.

    If results of the GGT blood test are abnormal, the physician may order a second GGT depending on the individual and the circumstances. Decreased levels of GGT are typically not cause for a concern and do not warrant special monitoring. Those with increased levels may undergo further testing to check the level of the other enzymes commonly found in the liver.

    Berk PD, Korenblat KM. Approach to the patient with jaundice or abnormal liver test results. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 150.

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