Blood biochemistry: gamma glutamyltransferase

Blood biochemistry: gamma glutamyltransferase
(gGT, Gamma glutamyltranspeptidase, GTP)

Overview

Membrane-associated enzyme.
Highest levels in renal tubular epithelial cells, canalicular surfaces of hepatocytes and bile duct epithelium - also present in pancreas and small intestine.
Hepatobiliary system is main source of serum GGT in health and disease.

Uses

In combination

Cholestasis.

Liver damage.

Sampling

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Source of test material

Standard venipuncture .
Romanowsky-type stains most commonly used for cytologic evaluation.

Quantity of test material

2 ml serum or plasma. Check with laboratory regarding minimum recommended volume for single test or in combination with other tests.

Quality control

Timing of test

Fast animal for 8-12 h before sampling to prevent sample lipemia.

Sample storage

Refrigerate prior to despatch.

Sample transport

Standard postal times adequate.
Package according to mailing regulations .
Avoid excessive temperatures.
If possible, separate serum/plasma prior to despatch.

Test(s)

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Methodologies

Vary between laboratories.

Availability

Widely available.

Validity

Sensitivity

Lower sensitivity than ALP in detection of liver disease, but greater specificity.

Specificity

Lower sensitivity than ALP in detection of liver disease, but greater specificity.

Technique (intrinsic) limitations

Test results most significant in conjunction with other laboratory results and clinical findings.
Canine colostrum contains large amounts of GGT; with colostral absorption in neonates see marked increases in GGT levels (<1000X).

Result data

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Normal (reference) values

US

Example of reference interval: 1.2-6.9 u/l.
Reference interval may vary with method/laboratory.

Abnormal values

Increased [GGT]

Liver damage (especially chronic, eg cirrhosis ):
- Rise in GGT often lags 2-3 days behind ALT and ALT increases.
Cholestasis.

Errors and Artifacts

Drug induced increase

Increase less dramatic than increase in ALP :
- Glucocorticoids.
- Phenytoin .
- Barbiturates .

Sources

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Publications

Refereed papers

Center S A, Slater M R, Mainwarren T et al(1992) Diagnostic efficacy of serum alkaline phosphatase and gamma-glutamyltransferase in dogs with histologically confirmed hepatobiliary disease - 270 cases (1980-1990). JAVMA 201 , 1258.

Other sources of information

Ettinger S J & Feldman E C (eds) (2000) Textbook of Veterinary Internal Medicine. 5th edn. Philadelphia: W B Saunders & Co.
Kaneko J J, Harvey J W & Brass M L (eds) (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Boston: Academic Press.
Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine. Clinical Pathology. 3rd edn. Iowa: Iowa University Press.

Vetstream contributor(s)

Dr Kathleen P Freeman DVM MS PhD , Idexx Laboratories, PO Box 4, Wetherby, West Yorkshire LS22 4ZR, UK.

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	Blood biochemistry: alanine aminotransferase (SGPT ALT)
	Blood biochemistry: alkaline phosphatase (ALP)
	Blood biochemistry: aspartate aminotransferase (AST)
	Jugular venipuncture
	Liver: chronic disease
	Liver: cirrhosis
	Phenytoin
	Primidone
	Transportation of diagnostic specimen

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