γ-Glutamyl Transferase (GGT)
Also known as: Gamma-Glutamyl Transferase, Glutamyl Transpeptidase
Use
A biliary enzyme that is especially useful in the diagnosis of obstructive jaundice, intrahepatic cholestasis, and pancreatitis.1 GT is more responsive to biliary obstruction than are aspartate aminotransferase (AST) (SGOT) and alanine aminotransferase (ALT) (SGPT).
Special Instructions
Patients should fast for eight hours prior to specimen collection to avoid false elevations, particularly if on phenytoin or phenobarbital therapy. Alternate tests like leucine aminopeptidase (LAP) or 5' nucleotidase are recommended under such circumstances.
Limitations
GGT levels can be artificially altered by external factors like acetaminophen toxicity which causes an in vivo increase. While GGT can signify liver involvement in metastases, its absence does not entirely rule out liver disease. GGT is not consistently elevated in cases with lymphoma without liver involvement. Additionally, GGT may not indicate metastasis uniformly, as seen in some colorectal carcinoma cases where only 81% of progressive diseases showed abnormal GGT levels.
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 2324-2
- 2324-2
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.7 mL
Container
Red-top tube, gel-barrier tube, or green-top (lithium heparin) tube.
Collection Instructions
Separate serum or plasma from cells within 45 minutes of collection.
Patient Preparation
The patient should fast for eight 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.
Storage Instructions
Maintain specimen at room temperature.
Causes for Rejection
Gross hemolysis; improper labeling; gross lipemia
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |