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Protein S Activity
Test Code1779X
CPT Codes
85306
Preferred Specimen
1 mL frozen plasma collected in 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL
Instructions
Centrifuge light blue-top tube for 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcL). Freeze immediately and ship on dry ice.
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen -20° C: 30 days
Frozen -70° C: 1 year
Refrigerated: Unacceptable
Frozen -20° C: 30 days
Frozen -70° C: 1 year
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolysis • Received thawed • Received room temperature • Received refrigerated
Methodology
Clot Detection
Setup Schedule
Set up: Mon-Sat; Report available: 1-3 days
Limitations
Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: decrease; Heparin (UFH or LMWH): may falsely increase at values approximately greater than 1.0 IU/mL; Dabigatran or Argatroban (Thrombin Inhibitors): may falsely increase; Rivaroxaban or Apixaban (Factor Xa Inhibitors): may falsely increase.
Clinical Significance
The congenital or acquired deficiency of Protein S increases the risk for thromboembolism, owing to a decrease of blood anticoagulant potential. It results in recurring thrombotic episodes. A decrease of Protein S leads to a greater risk of thromboembolism.
