Ordering Recommendation

Acceptable test to detect and subtype protein C deficiency. Do not order if individual has been on warfarin therapy in the previous 2-4 weeks.

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Lt. blue (sodium citrate). Refer to Specimen Handling at aruplab.com for hemostasis/thrombosis specimen handling guidelines.

Specimen Preparation

Transfer 2 mL platelet-poor plasma to an ARUP Standard Transport Tube. (Min: 1 mL)

Storage/Transport Temperature

CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.

Unacceptable Conditions

Serum. EDTA plasma, clotted or hemolyzed specimens.


Ambient: 4 hours; Refrigerated: Unacceptable; Frozen at -20°C: 3 months, at -70°C: 6 months


Electromagnetic Mechanical Clot Detection/Enzyme-Linked Immunosorbent Assay




1-5 days

Reference Interval

By report

Interpretive Data

Patients on warfarin may have decreased protein C values. Patients should be off warfarin therapy for two weeks for accurate measurement of protein C levels. Artificially increased functional protein C values may be due to heparin therapy or the presence of direct thrombin inhibitors or factor Xa inhibitors.

Compliance Category



If Protein C functional is decreased, then Protein C, Total Antigen, will be added. Additional charges apply.

Hotline History


CPT Codes

85303; if reflexed, add 85302


Component Test Code* Component Chart Name LOINC
0030113 Protein C Functional 27819-2
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • Protein C Profile
  • Protein C, functional and total
Protein C, Functional with Reflex to Protein C, Total Antigen