GAMMA-GLUTAMYL TRANSFERASE (GGT)
Definition
The liver works as the body's filter, removing toxins from the blood, processing nutrients and regulating its metabolism. When the liver is inflamed or damaged, enzymes including gamma-glutamyl transferase (GGT) leak from the liver cells into the bloodstream. As a result, elevated levels of GGT in the bloodstream can indicate the presence of liver disease, which may have been caused by heavy alcoholism, fatty liver disease (alcohol or non-alcohol related), hepatitis, or a combination of other causes.1,2 GGT is used widely to determine liver damage3 and is a sensitive indicator of heavy alcohol intake.4
The GGT test measures the amount of GGT circulating in the blood at the time of the test.
Population
GGT results were obtained for selected persons aged 12 years and over, who agreed to participate in the National Health Measures Survey (NHMS) and provided a blood sample. Fasting was not required for this test.
Methodology
A blood sample was collected from participants and GGT levels were measured at the Douglass Hanly Moir (DHM) laboratory.
There is no consensus on the cut off reference values for defining abnormal GGT levels for the Australian population, as there are currently a number of different methods that can be used to measure GGT. As such, cut off reference values for normal and abnormal results were sourced from DHM laboratory reference ranges.
In the NHMS, the following definitions were used for serum GGT:
Cut off points for GGT for females in the NHMS
|
 | GGT levels for females
(U/L) |
|
| Normal (12-14 years) | ≤30 |
| Abnormal (12-14 years) | >30 |
| Normal (15 years and over) | ≤35 |
| Abnormal (15 years and over) | >35 |
|
Cut off points for GGT for males in the NHMS
|
| GGT levels for males
(U/L) |
|
| Normal (12-14 years) | ≤30 |
| Abnormal (12-14 years) | >30 |
| Normal (15-17 years) | ≤40 |
| Abnormal (15-17 years) | >40 |
| Normal (18 years & over) | ≤50 |
| Abnormal (18 years & over) | >50 |
|
Further test information about the analysis method and machine used to measure GGT levels is available in Excel spreadsheet format in the
Downloads page of this product.
Data items
The data items and related output categories for this topic are available in Excel spreadsheet format from the
Downloads page of this product.
Interpretation
Points to be considered when interpreting data for this topic include the following:
- GGT results do not confirm a specific diagnosis without consultation with a health professional.
- There are a number of different test methods for measuring GGT, which may produce different results. The data from this topic should therefore be used with caution when comparing GGT results from other studies using a different test method or equation.
Comparability with other surveys
The NHMS is the first ABS survey to collect biomedical data on GGT levels.
GGT data has been collected in other non-ABS surveys. However, caution must be taken when interpreting results due to the differences in scope, assay and the instrument used, and any thresholds applied in the final analysis.
ENDNOTES
1 Everhart J and E Wright 2012.
Association of γ-glutamyltransferase (GGT) activity with treatment and clinical outcomes in chronic hepatitis C (HCV). Hepatology: Official Journal of the american Association for the Association for the study of Liver Diseases.
2 Torkadi P, Apte IC and AK Bhute 2013,
Biochemical Evaluation of Patients of Alcoholic Liver Disease and Non-alcoholic Liver Disease. Indian Journal of Clinical Biochemistry.
3 Department of Health and Aging 2011,
Biomedical Component of the Australian Health Survey: Public health objectives, <
http://www.health.gov.au/internet/main/publishing.nsf/Content/health-pubhlth-strateg-food-monitoring.htm/$File/Biomedical%20component%20AHS-public%20health%20objectives.pdf>, Last accessed 13/11/2013.
4 Whitfield JB 2001,
Gamma glutamyl transferase. Critical Reviews in Clinical Laboratory Sciences
. 38:4 pp 263-355.<
http://152.98.160.29/contents/p/staff/JW087.pdf>, Last accessed 13/11/2013.
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