Protein S Activity, Plasma
Use
The test is useful for second-order testing for diagnosis of congenital or acquired protein S deficiency, serving as an adjunct to initial testing based on the results of protein S antigen assay. It is also used for evaluating patients with a history of venous thromboembolism. Protein S is a vital part of the plasma anticoagulant system that acts as a necessary cofactor to activated protein C in the proteolytic inactivation of procoagulant factors Va and VIIIa.
Special Instructions
Patients must not be receiving Coumadin as it may interfere with protein S activity results. Specimen collection should follow specific guidelines including immediate freezing of the plasma below -40 degrees C no later than 4 hours after collection. If not ordered electronically, a printed Coagulation Test Request form (T753) must be sent with the specimen.
Limitations
Direct-acting oral anticoagulants and other interfering substances may cause protein S activity to appear spuriously normal or elevated. Acute or chronic inflammation, and other patient conditions can decrease protein S activity. It is preferable not to test for protein S deficiency during acute illness, pregnancy, or postpartum, and testing should be delayed for at least 30 days after stopping warfarin therapy.
FDA ApprovedNew York Approved
Methodology
Automated Analyzer (Coagulation)
Biomarkers
LOINC Codes
- 27822-6
- 27822-6
Result Turnaround Time
1-4 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
0.5 mL
Container
Plastic vial
Collection Instructions
Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again. Aliquot plasma into a plastic vial leaving 0.25 mL in the bottom of the centrifuged vial. Freeze specimen immediately (no longer than 4 hours after collection) below -40 degrees C.
Patient Preparation
Patient must not be receiving Coumadin.
Causes for Rejection
Gross hemolysis, gross lipemia, or gross icterus
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 14 days |