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Protein C Activity Assay

Protein C is a plasma anticoagulant factor required for maintenance of hemostatic balance. Protein C is synthesized in the liver and measurement of protein C activity aids in the diagnosis of thrombotic disorders and liver disease.

Protein C as a Biomarker of Liver Function

Recent studies indicate that protein C deficiency is a marker of liver disease in dogs. Protein C deficiency develops in dogs with hepatic synthetic failure and in portosystemic shunting disorders.

The protein C activity assay is especially useful as a non-invasive measure of portal blood flow. Dogs with congenital portosystemic vascular anomalies (PSVA) typically have low protein C activity, with values < 70% of normal. Although clinical signs and chemistry profiles of dogs with PSVA and microvascular dysplasia are similar, the finding of low protein C activity supports a diagnosis of PSVA. Furthermore, protein C activities can be monitored after shunt ligation to assess restoration of portal blood flow.

Sample Requirements

Submit 0.5 to 1.0 mL of citrate plasma, shipped overnight on a cold pack

Test Turnaround and Costs

Same-day reporting: the test is run daily (M-F) with results faxed out as soon as the assay is complete

Protein C Activity assay fee

Test Principle

Test plasma is treated with a venom-derived activator, and the amount of functional protein C produced is measured in a chromogenic assay system. Results are reported as % protein C activity compared to a same-species standard. Protein C activity assays are routinely offered for dogs, cats, and horses. Please call for information on other species.


  • Toulza O, Center SA, Brooks MB, Warner K, Deal W. Protein C deficiency in dogs with liver disease. Proceedings of the 22 nd Annual ACVIM Forum, Minneapolis, MN 2004; p. 866-867.
  • de Laforcade AM, Shaw SP, Freeman LM, Brooks MB, Rozanski EA, Rush JE. Coagulation parameters in dogs with naturally occurring sepsis. J Vet Intern Med 2003;17:674-679.
  • Mack CL, Superina RA, Whitington PF. Surgical restoration of portal flow corrects procoagulant and anticoagulant deficiencies associated with extrahepatic portal vein thrombosis. J Pediatr 2003;142:197-199.
  • Kottke-Marchant K, Comp P. Laboratory issues in diagnosing abnormalities of protein C, thrombomodulin, and endothelial cell protein C receptor. Arch Pathol Lab Med. 2002; 126:1337-48