Laboratory Medicine Program

Protein S Free (Antigen)
(Free Protein S Antigen, PS)

Clinical Decription:
Protein S (PS) is a vitamin K dependent plasma protein, produced in the liver that serves as a cofactor for the anticoagulant activity of activated protein C in the degradation of factors Va and VIIIa. PS in its bound form to C4Bp is inactive. Congenital and acquired deficiencies of free PS are associated with a hypercoagulable state. Hereditary heterozygote PS levels are approximately 50%. Acquired PS is seen in liver disease, disseminated intravascular coagulation (DIC), estrogen therapy, pregnancy, vitamin K deficiency or antagonism.

Method: Latex immunoturbidimetric Assay; Siemens Sysmex CS-5100

Component Tests Used: n/a

Reference Ranges Used:
Male > 0.68 IU/mL | Female > 0.60 IU/mL

Specimen Type: Citrated plasma
Collected In: 3.2% Sodium Citrate
Volume: 1.0 mL (minimum: 1.0 mL)

Shipping: Send frozen on dry ice.

Special Instructions: Patient should be fasting, if possible. Anticoagulants should be held for a requisite amount of time prior to testing to ensure no anticoagulant effect on the plasma. The specimen must be double-centrifuged to obtain a platelet-poor plasma specimen (Plt <10x10E9/L): 1. Immediately centrifuge specimen at 1500xG for 10 minutes. 2. Separate the plasma from the platelet/buffy coat and transfer into a clean plastic tube. 3. Centrifuge the separated plasma at 1500xG for 10 minutes. 4. Transfer 1.0 to 2.0 mL of the double-centrifuged plasma into a clean plastic tube, leaving approx. 200 uL for discard. 5. Freeze plasma aliquot immediately for storage. Maintain frozen for shipping and handling.

Testing Schedule(s): Weekly.

Turnaround Time: 10 Business days

For more information, call 416.340.5227 or 1.866.865.5227