Gamma Glutamyl Transpeptidase (GGT)
| Gamma Glutamyl Transpeptidase (GGT) | | | |
| Number | | 001958 |
| CPT | | 82977 |
| Synonyms | | Gamma GT ; GGT ; GT |
| Specimen | | Serum |
| Volume | | 1 mL |
| Minimum Volume | | 0.5 mL |
| Container | | Red-top tube or gel-barrier tube |
| Collection | | Separate serum from cells within 45 minutes of collection. |
| Storage Instructions | | Maintain specimen at room temperature. |
| Patient Preparation | | The patient should fast for 8 hours prior to collection of the specimen. Since there are false elevations in patients on phenytoin and phenobarbital, such patients would be better served with orders for one of the alternate tests - leucine aminopeptidase (LAP) or 5′ nucleotidase. |
| Causes for Rejection | | Gross hemolysis; improper labeling; gross lipemia |
| Reference Interval | | - Male: 0-65 IU/L
- Female: 0-60 IU/L
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| Use | | A biliary enzyme that is especially useful in the diagnosis of obstructive jaundice, intrahepatic cholestasis, and pancreatitis.1 GGT is more responsive to biliary obstruction than are aspartate aminotransferase (AST) (SGOT) and alanine aminotransferase (ALT) (SGPT). Increased in hepatoma and carcinoma of pancreas. Useful in diagnosis of metastatic carcinoma in the liver. Increasing levels in carcinoma patients relate to tumor progression, and diminishing levels to response to treatment.2 CEA, alkaline phosphatase, and GGT used together are useful markers for hepatic metastasis from breast and colon primaries. GGT is elevated in some instances of seminoma. Useful in diagnosis of chronic alcoholic liver disease, but some heavy drinkers do not have GGT increases. Serial determinations of serum GGT, AST, and ALT levels can distinguish recovering alcoholics who resume drinking from those who remain abstinent.3,4 Increase in body mass is positively correlated with increased GGT levels.5 With MCV of red cells, GGT is useful as a test for alcoholism. GGT is the test for cholestasis during or immediately following pregnancy. Commonly elevated in cirrhosis and hepatitis. The transaminases, AST and ALT rise higher in acute viral hepatitis; these tests with GGT and other parameters are best used together in work-up of liver disease. Increased in systemic lupus erythematosus.2 Very high levels are common in primary biliary cirrhosis. High GGT is found in infants with biliary atresia. It is increased with hyperthyroidism and decreased in those with hypothyroidism.6 GGT is comparable in many ways to two other biliary tests, LAP and 5′ nucleotidase. In some cases, five tests (including alkaline phosphatase and bilirubin) are necessary to evaluate the biliary tract. GGT usually is the most sensitive. In ascitic fluid, very high GGT is said to suggest hepatoma as opposed to cirrhosis or liver metastases. |
| Limitations | | Acetaminophen toxicity has been reported to cause an in vivo increase. The combination of high alkaline phosphatase and normal GGT does not rule out liver disease completely. Activity is not significantly increased in sera of patients with lymphoma (unless there is hepatic involvement by the lymphoma). Baden et al concluded that as a preoperative test for metastasis with colorectal carcinoma, GGT is unsatisfactory.7 As part of a evaluation for carcinoma patients, 19% of GGT results from patients with progressive disease were not abnormal, and 4% of values from patients without evidence of tumor were high.2 |
| Methodology | | Kinetic |
| Additional Information | | GGT is helpful to work up elevated alkaline phosphatase values. GGT is a biliary excretory enzyme which is more specific for hepatic disease than is alkaline phosphatase. It is normal in most instances of renal failure.8 GGT has no origin in bone or placenta, unlike alkaline phosphatase, and age beyond infancy does not influence GGT levels. Activity of GGT is highest in obstructive liver disease. It is commonly elevated in patients with infectious mononucleosis. When GGT and alkaline phosphatase are both high, but one is disproportionately elevated, suspect the possibility of drug-induced cholestasis (including alcoholism if it is GGT which is much higher). GGT, postprandial glucose, and triglyceride bear some correlation in certain groups of patients, including alcoholism and diabetes mellitus. Treatment of hypertriglyceridemia may also lead to decreased GGT. GGT is normal in normal children, adolescents, and in pregnant women. Unlike AST, it is not elevated in skeletal muscle disease. |
| Footnotes | | - Stein TA, Burns GP, and Wise L, “Diagnostic Value of Liver Function Tests in Bile Duct Obstruction,” J Surg Res, 1989, 46(3):226-9.
- Sahm DF, Murray JL, Munson PL, et al, “Gamma-Glutamyltranspeptidase Levels as an Aid in the Management of Human Cancer,” Cancer, 1983, 52(9):1673-8.
- Irwin M, Baird S, Smith TL, et al, “Use of Laboratory Tests to Monitor Heavy Drinking by Alcoholic Men Discharged From a Treatment Program,” Am J Psychiatry, 1988, 145(5):595-9.
- Frimpong NA and Lapp JA, “Effects of Moderate Alcohol Intake in Fixed or Variable Amounts on Concentration of Serum Lipids and Liver Enzymes in Healthy Young Men,” Am J Clin Nutr, 1989, 50(5):987-91.
- Robinson D and Whitehead TP, “Effect of Body Mass and Other Factors on Serum Liver Enzyme Levels in Men Attending for Well Population Screening,” Ann Clin Biochem, 1989, 26(Pt 5):393-400.
- Schaffner F, “Tests Related to the Liver,” Gastroenterology, 1985, 410-26.
- Baden H, Andersen B, Augustenborg G, et al, “Diagnostic Value of Gamma-Glutamyl Transpeptidase and Alkaline Phosphatase in Liver Metastases,” Surg Gynecol Obstet, 1971, 133(5):769-73.
- Lum G and Gambino SR, “Serum Gamma-Glutamyl Transpeptidase Activity as an Indicator of Disease of Liver, Pancreas, or Bone,” Clin Chem, 1972, 18(4):358-62
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