Protein S Antigen, Free


Abbrev Code:PSF   
Order Code:LAB492Order Name:Protein S Antigen Free
Synonyms:Free Protein S
Methodology:Latex immunoassay/Immuno-turbidmetric assay
CPT Codes: 85306 x1, 85306 x1
Turnaround Time:Turnaround time is 4 days, testing performed 2 days per week. With pre-notification, STATs are done within 1 hour after receipt in the testing laboratory.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens


Collection Instructions

Specimen:Blood
Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube.
Minimum\Peds Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube.
Container:Blue Na Citrate, 3.2% - fill to fill line on tube
Collection Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Causes for Rejection:Underfilled tubes, overfilled tubes, clotted specimens, not received or processed and frozen within 4 hours of collection or, specimen thawed during transit.


Processing and Shipping

Specimen Processing:
  • Process for Platelet Poor Plasma within 4 hours of collection.
  • Aliquot plasma, place clear tape around label, and freeze at -20C or on dry ice within 4 hours of collection.
  • If multiple tests are collected on 1 blue top, split each blue top into 2 aliquots. Minimum 0.5 mL per tube.
  • A maximum of 6 aliquots are needed per collection.
     
See link to Specimen Collection and Processing for Coagulation Specimens.
Shipping Instructions:
  • Ensure specimen is frozen before shipping.
  • Ship on dry ice, sample must remain frozen during shipping.
     
See link to Specimen Collection and Processing for Coagulation Specimens.
Test Performed at or Referral Lab UM Special Coag (K)  (UMMC East Bank)


Interpretive

Critical Range:Less than 20% (for 5 days and older).
Reference Range:

 

Protein S Free LIA

Newborn

33-67%

1 – 4 d

24-48%

5 – 29 d

36-64%

30 – 89 d

48-78%

90 d – 10 y

60-135%

11 y – adult, Male

70-148%

11 y – adult, Female

55-125%

 

 

Use:Protein S is a Vitamin K dependent plasma glycoprotein that serves as the cofactor for the anticoagulant function of activated Protein C inactivating activated Factors 5 and 8. Since it is Vitamin K dependent, it is decreased in warfarin therapy or Vitamin K deficiency. Protein S deficiency is a risk factor for thromboembolism. Severe deficiency may cause purpura fulminans. Protein S circulates in plasma in two forms: 40% is free Protein S, 60% is bound to C4B binding protein. Only the Free has cofactor activity for Protein C, therefore, it is the preferred method for measuring Protein S.


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