Last Updated October 11th, 2019
What is Gamma-Glutamyl Transferase (GGT)?
Gamma-glutamyltransferase is an enzyme found in the cell membranes of various tissues. It plays an important role in the metabolism of glutathione-a powerful antioxidant present in the cells of the body.
Gamma-glutamyltransferase was first identified in the kidney tissues. It is also present in tissues of many other organs including liver, spleen, heart, brain, seminal vesicles, etc. Though the highest concentration of GGT is seen in kidneys, it is of great importance in detecting the level of activity of liver cells. GGT is a serum marker widely used to determine the functioning of liver cells, especially in disorders involving alcohol abuse.
What is measured by a GGT Test?
The gamma-glutamyltransferase test is a blood test that measures the levels of GGT in your blood. Elevated levels of GGT in blood may indicate liver injury. The normal values of GGT range from 0 to 30 IU/L.
Why has my doctor ordered GGT Test for me?
A GGT test is usually performed as a part of other liver function tests including alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase, bilirubin, albumin and prothrombin time.
Your physician may prescribe a GGT test for you in the following cases-
– You are showing signs of a liver disorder-namely jaundice, dark urine/white stools, chronic fatigue, nausea, vomiting, loss of appetite, chronic itching, abdominal pain.
– You are consuming excessive amounts of alcohol
– You have a family history of liver diseases
– You are taking medications which are hepatotoxic (this is common when a person is prescribed anti-tubercular drugs most of which are harmful to the liver)
What are the causes of elevated gamma-glutamyl transferase?
– Hepato-biliary disorders
– Exposure to hepatotoxins
– Congestive cardiac failure and myocardial infarction
– Renal failure
How common is NAFLD or Non-Alcoholic Fatty Liver Disease in India?
NAFLD is counted as the most common cause of chronic liver disease in the world. In India, NALFD is found in 9-32% of the general population. Obese and/or diabetic patients are more likely to suffer from this disease.
How should I prepare for a GGT Test? What are the precautions that I need to undertake?
No, specific preparation is required. You need to discuss with the physician your medical history. As the GGT test is a blood test and involves the standard techniques of venipuncture, you need to inform your physician if you are
– On any blood thinners
– Suffering from any coagulopathy
– Allergic to any drug.
Do I need to fast overnight?
Yes. Your physician will advise you to fast for 8 hours prior to the test. He may also ask you to abstain from consuming alcohol for at least 24 hours before the test. This is debatable though, as GGT levels return to normal only after at least a month of abstinence from alcohol. Smoking is not desirable before a GGT test as it raises GGT levels in the blood.
Can I undergo GGT Test if I am pregnant?
It is perfectly safe to undergo the GGT test in pregnancy. In fact, elevated GGT levels are an independent risk factor for gestational diabetes mellitus in high-risk pregnant women.
Can children undergo GGT Test?
Yes, though it is to be kept in mind that the normal GGT values are raised in infants; up to 6-7 times the upper limit of the adult reference range (GGT levels reach the adult value by 7 months of age).
How is the actual GGT Test performed?
– A GGT test is rarely performed as a stand-alone test. It is normally a part of the “liver function tests”. It is a blood test carried out on an outpatient basis unless the patient is already admitted to a hospital.
– The technician will apply a tourniquet proximally to the site chosen for venipuncture. This makes the veins more prominent, allowing easier access.
– The area is cleaned with a disinfectant. A sterile needle is used to puncture the vein and draw about 5 ml of blood.
– The pressure is applied to the vein with sterile gauze after the needle is withdrawn. The tourniquet is released. The blood sample is collected in a vial.
– The entire procedure is over in a few minutes. In obese patients, patients belonging to the geriatric age group and very young children, venous access is sometimes difficult, leading to more than one prick.
How long does it take for the result of a GGT test to be out?
The findings of a GGT test are available in a few hours.
What are the risks involved?
As is the case with any procedure involving venipuncture- bleeding, bruising and infection at the site of vascular invasion may be encountered. You may also experience mild nausea and dizziness at the sight of blood.
What are the advantages and limitations of the GGT Test?
|In isolated cases of an increase in alkaline phosphatase enzyme, GGT levels help in determining if the source is bone or the hepatobiliary system.|| |
Though GGT is a very sensitive test for liver injury, it is not very specific. Elevated GGT levels are seen in many disorders of non-hepatic origin.
|An elevated GGT in the presence of an AST/ALT ratio of 2:1 is highly indicative of alcoholic liver disease (ALD).||In patients suffering from hepatitis of infectious origin, the elevation in GGT levels is mild. (2 to 5 times).|
|In cases of obstructive jaundice, the increase in GGT levels occurs early and is more pronounced. The same is the case with metastatic cancers.||An elevated GGT level does not lead to the diagnosis of a specific disorder. It only indicates liver damage. Follow-up tests are required most of the time.|
As mentioned above, there are many medical conditions which lead to a rise in serum gamma-glutamyl transferase. Your physician will corelate the findings of this test with your clinical history and physical examination and reach at a conclusion. He may order further tests if the diagnosis is inconclusive.
What is the cost of performing a GGT test in India?
The cost of performing a blood test to determine GGT levels is around Rs 250 in India.
What are the other tests used to measure liver function?
The liver function tests commonly used to evaluate liver damage are as follows:
Name of the Liver enzyme/Test
|Serum Albumin||3.5 to 5.0 grams per deciliter (g/dL)|
|Serum Bilirubin|| |
0.1 to 1.2 milligrams per deciliter (mg/dL)
|Alanine transaminase (ALT)||7 to 55 units per liter (U/L)|
|Aspartate transaminase (AST)||8 to 48 U/L.|
|Alkaline phosphatase||40 to 129 U/L|
|Lactate dehydrogenase||122 to 222 U/L.|
|Prothrombin time||9.4 to 12.5 seconds|
|International normalized ratio (INR)||2.0 to 3.0|
Apart from the routine liver function tests displayed above, there are a few advanced tests currently limited to research centers. These quantitative tests include-indocyanine green clearance, antipyrine clearance, and galactose elimination capacity. These expensive tests have a long way to go before they can garner the support from the general physician.
What is the future of the GGT Test?
Gamma-glutamyltransferase, as a serum marker, has a utility which extends much beyond predicting the presence and extent of liver damage. Elevated GGT levels act as an early disease marker and can predict an increased risk to-
– Cardiac diseases
– Metabolic syndromes
– Gestational diabetes
– Damage due to environmental toxins
How can I keep my liver healthy?
The liver, the second largest organ in your body performs many complex functions that are vital for your survival. These include eliminating toxins from your body, metabolizing drugs, manufacturing proteins, maintaining optimum cholesterol levels and making bile.
The least you can do is to ensure that your liver remains hale and hearty. A few practices, if adhered to life-long can go a long way in keeping your liver in prime shape.
–Avoid alcohol– There is no safe limit of alcohol intake as far as the liver injury is concerned. Females are more prone to alcohol-induced liver damage.
– Wash your hands before having a meal– Hepatitis A and E are transmitted via contaminated food and water.
– Practice safe sex– Hepatitis B, C, and D are diseases transmitted by blood and body fluids.
– Do not indulge in drugs– Intravenous drug use can lead to Hepatitis B, C, and D.
– Get vaccinated against Hepatitis A and B.
– Maintain an active lifestyle. Obesity damages your liver in more ways than one.
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