Interferences
Protein S, free: Warfarin (Coumadin)
Protein S, activity:
Clot based assay results may be falsely elevated due to interferences from several anticoagulants (High level Heparin, direct oral anticoagulants, direct thrombin inhibitors). Warfarin will lead to falsely decreased results.
Warfarin (Coumadin) therapy should be discontinued two weeks prior and heparin therapy two days prior to sample collection.
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.
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
Protein S, free – Immuno-turbidometric
Protein S, activity - Clotting assay
Protein S, free (Antigenic):
Female: 50-134%
Male: 70-148%
Protein S, activity:
Female: 50 - 120%
Male: 60 - 120%
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 |
Decreased |
Decreased |
Decreased |
Type II |
Normal |
Normal |
Decreased |
Type III |
Decreased |
Normal |
Decreased |
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.
Reference:
Quality in Laboratory Hemostasis and Thrombosis. Kitchen, Steve, Olson, John D., and Preston, F. Eric. 2009 Blackwell Publishing Ltd, Sussex, UK. pg. 152.