Protein S Free, Antigen
Also known as: PRO S FREE
Use
The Protein S Free, Antigen test is used for detecting protein S deficiency. Protein S deficiency is a condition often associated with an increased risk of thrombosis due to impaired regulation of blood coagulation. Protein S is a vitamin K-dependent plasma glycoprotein that functions as a cofactor to activated protein C in the degradation of factors Va and VIIIa, which prevents excessive clot formation. This test is particularly significant for individuals suspected of having hereditary thrombophilia, along with assessing the impact of anticoagulants on coagulation testing. It is crucial not to conduct the test if the individual has been on warfarin therapy within the previous 2-4 weeks as warfarin affects protein S levels.
Special Instructions
The test should not be ordered if the individual has been on warfarin therapy in the previous 2-4 weeks due to the potential for decreased protein S values. Patients should ideally discontinue warfarin therapy at least two weeks before the test to ensure accurate results. This test requires critical frozen transport and separate specimens must be submitted when multiple tests are ordered.
Limitations
Decreased levels of free protein S can also be associated with other conditions such as disseminated intravascular coagulation (DIC), liver disease, pregnancy, and inflammatory syndromes. The test values may be affected by recent warfarin therapy, hence warfarin must be discontinued two weeks before testing to avoid false-low results.
FDA ApprovedNew York Approved
Methodology
Immunoassay (Microlatex Particle-Mediated Immunoassay)
Biomarkers
LOINC Codes
- 27821-8
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1.5 mL
Minimum Volume
1 mL
Container
ARUP standard transport tube
Collection Instructions
Transfer 1.5 mL platelet-poor plasma to an ARUP standard transport tube. (Min: 1 mL). Collect using Lt. blue (sodium citrate).
Patient Preparation
Patients should be off warfarin therapy for two weeks prior to testing to avoid decreased protein S values.
Storage Instructions
CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.
Causes for Rejection
Serum, EDTA plasma, clotted or hemolyzed specimens are unacceptable.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 4 hours |
| Refrigerated | Unacceptable |
| Frozen | 3 months |