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Protein S Activity

Protein S Functional

Test Codes

EPIC: LAB5206, Beaker: PSACT, Antrim: 19639

Department

Coagulation

Instructions

• The patient should be off warfarin for at least two weeks prior to specimen collection.
• Specimens with hematocrit values greater than 55% must have anticoagulant adjusted. Specimens must be re-collected using a specified whole blood to sodium citrate ratio. Contact the performing Laboratory for specific instructions.

Specimen Collection Criteria

Collect: A minimum of two (2) Light Blue-top 3.2% Sodium Citrate tube.

TUBES MUST BE FULL.

Physician Office/Draw Specimen Preparation

For optimal results, maintain whole blood specimen at room temperature (20-26°C or 68-78.8°F) prior to transport. Transport whole blood to the Laboratory within 4 hours of collection. If transport within 4 hours is not possible, the following procedure must be followed for accurate results:

1. Centrifuge the capped tubes at 1500 x g for 15 minutes.
2. Transfer plasma with plastic pipette into a plastic polypropylene centrifuge tube, cap and centrifuge an additional 15 minutes at 1500 x g to obtain platelet poor plasma (PPP) which has a platelet count less than 10 bil/L. Plasma with a platelet count of less than 10 bil/L is critical for accurate results.
3. Immediately remove only the top two-thirds of the PPP and transfer into a minimum of two (2) screw cap, 5 ml, 75 x 13 mm, round base, polypropylene transport tubes.
4. Freeze (-20°C/-4°F or below) the PPP immediately.
5. Transport frozen on DRY ICE. Specimen must remain frozen during transport. 

Preparation for Courier Transport

Transport: Whole blood at room temperature (20-25°C or 68-77°F), or plasma obtained through the process listed above, frozen (-20°C/-4°F or below).

Rejection Criteria

• Glass tubes and 3.8% Sodium Citrate tubes.
• Specimens that are clotted or grossly hemolyzed.
• Inappropriate specimen volume.
• Thawed or partially thawed specimens.

In-Lab Processing

Whole blood specimens must be processed as follows upon receipt in the Laboratory: 

1. Centrifuge the capped tubes at 1500 x g for 15 minutes.
2. Transfer plasma with plastic pipette into a plastic polypropylene centrifuge tube, cap and centrifuge an additional 15 minutes at 1500 x g to obtain platelet poor plasma (PPP) which has a platelet count less than 10 bil/L. Plasma with a platelet count of less than 10 bil/L is critical for accurate results.
3. Immediately remove only the top two-thirds of the PPP and transfer into a minimum of two (2) plastic transport tubes.

4. Test or freeze specimen according to lab protocol.

Storage

Specimen Stability for Testing:

Whole Blood
Room Temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Platelet Poor Plasma (PPP)
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): 30 days

Specimen Storage in Department Prior to Disposal:

Frozen (-20°C/-4°F or below): 30 days

Laboratory

Activity testing will be performed at Royal Oak Coagulation Laboratory.
Antigen testing will be sent to Mayo Clinic Laboratories in Rochester, MN. 

Performed

Monday, Thursday.
Results available within 4 days, or within 14 days if Protein S antigen test is required.

Reference Range

Protein S Activity
Females: 50-160%.
Males: 60-160%.

Test Methodology

Protein S Activity
Change in Optical Absorbance (IL ACL TOP Series).

Interpretation

• Heparin levels greater than 1.6 U/mL or low molecular weight heparin levels greater than 2.1 U/mL may cause false high Protein S values. 
• Acquired Protein S deficiency may be caused by pregnancy, estrogen use, nephrotic syndrome, and liver disease. Decreased Protein S levels may also be seen in newborns.
• Factor VIII greater than 250% can greatly decrease the Protein S result.
• If a decreased Protein S activity is obtained and the patient is not on Coumadin, a Protein S antigen (total and free) will also be performed.
• Direct Oral Anticoagulants may cause protein S levels to appear falsely normal or increased to the effect of these drugs on the coagulation cascade. This effect can mask a protein S deficiency.

Clinical Utility

Protein S is a naturally occurring, vitamin K-dependent inhibitor of coagulation. It acts as a cofactor of activated Protein C, thereby decreasing the ability of Factor V and VIII as procoagulants. Protein S deficiency is a cause of inherited thrombosis.

CPT Codes

85306. Add 85305 and 85306 if antigen is performed.

Contacts

Last Updated

10/3/2023