Protein S, free

Alphabetical Test listing

Protein S, free-5750

Protein S, free
Protein S, functional & free
Protein S, activity
Protein S, free

Warfarin (Coumadin)


Warfarin (Coumadin) therapy should be discontinued two weeks prior and heparin therapy two days prior to sample collection.

Sodium citrate (Na cit) plasma

 Lt blue Sodium citrate (Na Cit) - 2.7mL

If the patient has a hematocrit >55, a specially prepared Lt blue Sodium citrate (NaCit) tube must be used in place of the standard Lt blue Sodium citrate (NaCit) tube.

Hematocrit-Anticoagulant adjustments

1.5 mL
  • Do not draw from an arm with a heparin lock or heparinized catheter
  • Do not over or under fill tube as the ratio of anticoagulant to whole blood is critical

Coag – tube fill guidelines

  • Immediately following collection, mix sample thoroughly by gently inverting 8 - 10 times to prevent clotting

Microcentrifuge vial/tube in a Snap cap conical vial/tube and cap (Beaker sites)



Coagulation specimen transport vial/tube  (all other sites)



Frozen (strict)

Refrigerated - NO

  • Greiner tubes are not acceptable
  • Improper labeling (unlabeled or mislabeled)
  • Improper anticoagulant
  • Improperly filled tube
  • Hemolysis
  • Clotted specimen
  • Delay in transport
  • Improper storage/transport temperature
  • Patient on heparin > 1.0 IU/mL
AHL - Coagulation/Special Coagulation: V
Varies: 1 - 2 times/wk
Available STAT
3 - 5 days

Protein S, free – Immuno-turbidometric


Protein S, free (Antigenic):

Female: 55-124%

Male: 74-126%


Guidance for the evaluation and treatment of hereditary and acquired thrombophilia

Types of Heterozygous Protein S deficiency


Protein S, free Ag

Protein S, total

Protein S, activity

Type I




Type II




Type III





The three subtypes of heritable protein S deficiencies include both qualitative and quantitative defects. Type I is a quantitative defect resulting in decreased plasma antigen levels of both free and total protein S antigen. Type II is a qualitative defect with decreased protein S activity and normal levels of free and total protein S antigen. Type III is characterized by decreased free protein S antigen and protein S activity with normal levels of total protein S antigen. Type I and III protein S deficiency are much more common than type II (dysfunctional) protein S deficiency.

Acquired free protein S deficiency may be seen in certain inflammatory conditions and will most often have decreased levels of free protein S antigen and protein S activity, but normal to elevated total protein S antigen. The hemostatic implications for patients with acquired protein S deficiency are of unclear clinical significance.


Quality in Laboratory Hemostasis and Thrombosis. Kitchen, Steve, Olson, John D., and Preston, F. Eric. 2009 Blackwell Publishing Ltd, Sussex, UK. pg. 152.

85306 - Protein S, free antigenic