Protein S Activity

1779

1 mL frozen platelet-poor plasma collected in 3.2% sodium citrate (light blue-top) tube

0.5 mL

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.

Plastic vial

Frozen

Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days

Hemolysis

Set up: Tues-Sat; Report available: 1-3 days

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.

Protein S (PS) deficiency may be congenital or acquired and is associated with venous thrombosis. Acquired PS deficiency may occur with vitamin K antagonists/deficiency, liver disease, malignancy, consumptive DIC, surgery, trauma, and hepatic immaturity of the newborn. In addition, PS deficiency is physiologic in pregnancy.

Anticoagulant interference: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Vitamin K Antagonists (eg. warfarin):
decrease; Heparin (UFH or LMWH): no effect to falsely increased activity levels at higher levels; Dabigatran or Argatroban (Direct Thrombin Inhibitors): may falsely
increase activity; Rivaroxaban, Apixaban, Edoxaban (Factor Xa Inhibitors): may falsely increase activity.