Overview

• Membrane associated enzyme.
• Number of isoenzymes produced in a range of tissues (liver, kidney, intestine, placenta).
• Special procedures are necessary to determine isoenzymes.
• Levamisole inhibition or heat activation commonly used to separate hepatic from steroidal isoenzymes as cause of increased activity.
• May see overlap in steroid and hepatic isoenzymes in many types of disease so not always helpful in separating underlying cause.
• Increased plasma levels are derived from liver and bone.
• Good indicator of liver disease and cholestasis - increases before plasma bilirubin.
• Corticosteroids induce a specific isoenzyme from the liver (steroid-induced alkaline phosphatase - SIAP/sALP).

Sampling

Tests

Methodologies

• Method and normal range may vary between laboratories.
• Electrophoretic or other separation method necessary to measure activity of individual isoenzymes, especially SIAP.

Availability

• Widely available.
• Routine test - contact laboratory to confirm availability of SIAP measurement.

Validity

Sensitivity

• Sensitive indicator of cholestasis or hyperadrenocorticism, but not specific.

Technique (intrinsic) limitations

• Test results most significant when interpreted in conjunction with other laboratory results and clinical findings.

Result Data

Further Reading

Publications

Refereed papers

• Recent references from VetMedResource and PubMed.
• Center S A, Slater M R, ManWarren T et al (1992) Diagnostic efficacy of serum alkaline phosphatase and gamma-glutamyltransferase in dogs with histologically confirmed hepatobiliary disease - 277 cases (1980-1990). JAVMA 201, 1258.

Other sources of information

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