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Protein S Activity
Test CodePROTS
Alias/See Also
Protein S Functional
CPT Codes
85306
Preferred Specimen
Citrate BLUE (BLU)
Instructions
Collect whole blood in 3.2% buffered sodium citrate (9:1 blood to sodium citrate). Venipuncture must be atraumatic.
Specimen Stability
- Centrifuge at 4,500 RPM (high) for 10 minutes. Plasma platelet count should be less than 10,000. Test within 4 hours of collection.
- If testing is to be delayed more than 4 hours after collection, immediately separate plasma into a clean, polystyrene tube, cap and store below -20°C up to two weeks or -70°C up to 6 months.
- In patients with hematocrit values greater than 55%, the citrate concentration must be adjusted so that a proper plasma/anticoagulant volume is maintained.
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Reject hemolyzed, clotted, overfilled tubes or short draw (<90%) samples.
Methodology
Diagnostic Stago
Reference Range
1 day to 6 years: 12-93%
> 6 years: 54-131%
> 6 years: 54-131%
Clinical Significance
Protein S is a plasma vitamin-K-dependent protein that is synthesized in the liver as an inactive precursor. Protein S acts as the cofactor of activated protein C. In the presence of calcium this complex binds strongly to the phospholipid surfaces and thus regulates the coagulation process, inhibiting thrombin-stimulated factors V and VIII.
Protein S greatly potentiates protein C anticoagulant function, probably by increasing protein C affinity for phospholipid membranes.
In normal plasma, about 60% of Protein S is in complex with C4B binding Protein while the other 40% is in the free form. Only free Protein S has functional cofactor activity.
Protein S deficiency may be hereditary or acquired. Acquired deficiency may be observed during pregnancy, oral anticoagulant therapy, oral contraceptive use, in liver disease, in newborn infants as well as in other clinical
Protein S greatly potentiates protein C anticoagulant function, probably by increasing protein C affinity for phospholipid membranes.
In normal plasma, about 60% of Protein S is in complex with C4B binding Protein while the other 40% is in the free form. Only free Protein S has functional cofactor activity.
Protein S deficiency may be hereditary or acquired. Acquired deficiency may be observed during pregnancy, oral anticoagulant therapy, oral contraceptive use, in liver disease, in newborn infants as well as in other clinical
Performing Laboratory
CRMC Laboratory
