Protein C, Functional
Also known as: Functional Protein C, Protein C Activity (Chromogenic)
Use
Confirmation and characterization of protein C deficiency
Special Instructions
If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions. The patient should ideally not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.
Limitations
Individuals with heterozygous protein C (PC) deficiency may have low normal PC levels. Treatment with warfarin decreases the levels of vitamin K-dependent factors including PC, and levels start to drop after six hours of warfarin treatment, not returning to pretreatment levels until generally two weeks after cessation of therapy. Elevated factor VIII levels can normalize the aPTT and effectively reduce PC levels. PC levels may be falsely low in patients with the factor VLeiden mutation. Additionally, PC levels can become depleted due to coagulation activation, limiting testing utility during the immediate convalescent period after a thrombotic event. This test should not be used for patients on thrombin inhibitors such as hirudin and argatroban.
Methodology
Immunoassay (Chromogenic)
Biomarkers
LOINC Codes
- 27818-4
- 27818-4
Result Turnaround Time
2-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
Not provided
Container
Blue-top (sodium citrate) tube
Collection Instructions
Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio. The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood.
Patient Preparation
Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing. Do not draw from an arm with a heparin lock or heparinized catheter.
Storage Instructions
Freeze.
Causes for Rejection
Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 28 days |
Other tests from different labs that may be relevant