Protein C Assay FAQs

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Comparative Coagulation

Protein C Assay FAQs

Protein C Sample Submission FAQs

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Protein C Testing and Interpretation FAQs

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What sample is required for Protein C testing?

Separated citrate plasma (plasma from a blue top tube) is the only valid sample. DO NOT SUBMIT SERUM. Ship at least 0.5 mL of plasma in an insulated box with cold packs for overnight delivery.  See for detailed sampling instructions.

Does the patient have to be fasted?

No, fasting is not required for Protein C testing. However, marked lipemia and hemolysis can interfere with assay endpoint detection. It is best to draw a new sample if your separated plasma is severely hemolyzed (i.e. bright red plasma).

What is the turnaround time and cost for Protein C testing?

Protein C assays are performed daily and results reported within 24 hours of sample receipt. Refer to the AHDC test/fee list for current pricing.

What is the shipping address for Protein C testing?

Comparative Coagulation Section/AHDC
College of Veterinary Medicine, Cornell University
240 Farrier Road
Ithaca , NY 14853

Comparative Coagulation Section/AHDC
College of Veterinary Medicine, Cornell University
PO Box 5786
Ithaca , NY 14852-5786

How can I use the Protein C assay to diagnose dogs with portosystemic shunts?

Protein C deficiency is a marker of portosystemic shunting. While clinical signs, breeds at risk, and bile acid elevation are common to portosystemic shunting and microvascular dysplasia, Protein C deficiency develops primarily in dogs with congenital portosystemic shunts. Including Protein C in the diagnostic workup helps identify patients for imaging studies and ultimately shunt repair.

What is the best Protein C cutoff for differentiating shunts from microvascular dysplasia?

Based on the Cornell University caseload, Protein C values below 70% are found in dogs with shunts whereas dogs with MVD typically have values above 70%. The combined findings of Protein C < 70%, low cholesterol, and low MCV (mean corpuscular volume) further support the presence of a shunt.

Are there other diseases that cause Protein C deficiency?

Yes. Protein C deficiency develops in patients with hepatic synthetic compromise, vitamin K deficiency from any cause, and some DIC and sepsis cases.  Liver failure causes severe Protein C deficiency (< 50%) and levels may fall early after exposure to hepatotoxins.

Where can I learn more about Protein C?

See the Coagulation Lab’s Protein C web page for more on Protein C’s role in disease and health, assay methodology, a veterinary bibliography, and external links.