From the Guidelines
Testing Gamma-Glutamyl Transferase (GGT) is highly valuable in patients with elevated Liver Function Tests (LFTs) as it helps distinguish between hepatic and non-hepatic causes of alkaline phosphatase (ALP) elevation. When a patient presents with elevated LFTs, particularly ALP, measuring GGT can confirm whether the elevation originates from the liver or from other sources such as bone or placenta. GGT is specifically found in liver cell membranes and biliary epithelial cells, making it a sensitive marker of hepatobiliary disease, as noted in the 2023 study by the American College of Radiology 1.
Some key points to consider when evaluating the utility of GGT testing in patients with elevated LFTs include:
- GGT can indicate whether pathologically elevated ALP is of hepatic or nonhepatic origin, as it is not found in bone, unlike ALP 1.
- Concomitantly elevated GGT can help confirm that an elevated ALP originates from the liver and indicates cholestasis, guiding further diagnostic steps such as imaging of the biliary tree 1.
- GGT elevation can detect subtle liver damage before other LFTs become abnormal and can help monitor medication-induced liver injury, especially with certain drugs 1.
- The test is simple to perform, widely available, and relatively inexpensive, making it a practical addition to the standard liver panel when investigating abnormal LFTs.
In the context of alcoholic liver disease, GGT is often disproportionately elevated compared to other liver enzymes due to alcohol's enzyme-inducing effects, as discussed in the 2012 EASL clinical practical guidelines for the management of alcoholic liver disease 1. However, the most recent and highest quality evidence from 2023 emphasizes the role of GGT in distinguishing between hepatic and non-hepatic causes of ALP elevation, making it a crucial test in the evaluation of elevated LFTs 1.
From the Research
Utility of Testing GGT in Patients with Elevated LFTs
- The utility of testing Gamma-Glutamyl Transferase (GGT) in patients with elevated Liver Function Tests (LFTs) is to help identify the underlying cause of liver disease 2.
- GGT is often used in conjunction with other liver enzymes, such as alkaline phosphatase (AP), to distinguish between hepatocellular and cholestatic patterns of liver injury 2, 3.
- Elevated GGT levels can indicate cholestasis, alcohol-induced liver disease, or other conditions that affect the biliary system 2, 4.
- However, GGT is not liver-specific and can be elevated in other conditions, such as pancreatic disease or renal disease 2.
Interpretation of GGT Results
- The interpretation of GGT results should be done in conjunction with other liver enzymes and clinical presentation 5, 3.
- A hepatocellular pattern of liver injury is characterized by elevated transaminases (AST and ALT), while a cholestatic pattern is characterized by elevated AP and GGT 2, 3.
- The magnitude of GGT elevation can also provide clues to the underlying diagnosis, with mild elevations often seen in asymptomatic patients and more severe elevations indicating more significant liver disease 6, 4.
Clinical Application
- Testing GGT can help clinicians to narrow down the differential diagnosis and guide further evaluation and management of patients with elevated LFTs 5, 3.
- The American College of Gastroenterology recommends that clinicians assess abnormal liver chemistries, including GGT, to guide the evaluation of patients with liver disease 3.
- Accurate interpretation of GGT results, in conjunction with other liver enzymes and clinical presentation, can help clinicians to provide prompt and appropriate treatment, which can improve patient outcomes 4.