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Test Code SFX Protein S Activity, Plasma


Specimen Required


Specimen Type: Platelet-poor plasma

Patient Preparation: Patient must not be receiving Coumadin.

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing

2. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.

3. Aliquot plasma into a plastic vial leaving 0.25 mL in the bottom of centrifuged vial.

4. Freeze specimen immediately (no longer than 4 hours after collection) below -40° C.


Secondary ID

617792

Useful For

Second-order testing for diagnosis of congenital or acquired protein S deficiency, ie, as an adjunct to initial testing based on results of protein S antigen assay (free protein S antigen, with or without total protein S antigen assay)

 

Evaluating patients with a history of venous thromboembolism

Method Name

Optical Clot-Based

Reporting Name

Protein S Activity, P

Specimen Type

Plasma Na Cit

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen 14 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Clinical Information

Protein S is a vitamin K-dependent plasma glycoprotein synthesized predominantly within the liver. Protein S is also synthesized in endothelial cells and present in platelets. As a part of the plasma anticoagulant system, protein S acts as a necessary cofactor to activated protein C (APC) in the proteolytic inactivation of procoagulant factors Va and VIIIa. About 60% of the total plasma protein S antigen circulates bound to C4b binding protein (C4b-BP), while the remainder circulates as “free” protein S. Only free protein S has anticoagulant activity.

 

Congenital protein S deficiency is an autosomal codominant disorder that is present in 1% to 3% of patients with venous thromboembolism. Heterozygous protein S deficiency carriers have, approximately, a 10-fold increased risk of venous thromboembolism. Other phenotypic expressions of heterozygous congenital protein S deficiency include recurrent miscarriage, complications of pregnancy (preeclampsia, abruptio placentae, intrauterine growth restriction, and stillbirth) and, possibly, arterial thrombosis. Three types of heterozygous congenital protein S deficiency have been described according to the levels of total protein S antigen, free protein S antigen, and protein S (APC cofactor) activity in plasma.

 

 Table. Types of heterozygous protein S deficiency

Type

Free protein S antigen

Total protein S antigen

Protein activity

I

Decreased

Decreased

Decreased

II

Normal

Normal

Decreased

III

Decreased

Normal

Decreased

 

Type I and III protein S deficiency are much more common than type II (dysfunctional) protein S deficiency. Type III protein S deficiency appears to be partly due to variants within the protein S binding region for C4b-BP.

 

Homozygous protein S deficiency is rare but can present as neonatal purpura fulminans, reflecting severe intravascular coagulation and fibrinolysis/disseminated intravascular coagulation (ICF/DIC) caused by the absence or near absence of plasma protein S.

 

Acquired deficiency of protein S is much more common than hereditary protein S deficiency and is generally of unknown hemostatic significance (ie, uncertain thrombosis risk). Among the many causes of acquired protein S deficiency are:

-Vitamin K deficiency

-Oral anticoagulant therapy

-Acute illness (eg, acute thrombosis, recent surgery, or other disorder associated with acute inflammation)

-Liver disease

-ICF/DIC

-Thrombotic thrombocytopenic purpura

-Pregnancy, oral contraceptive, or estrogen therapy

-Nephrotic syndrome

-Sickle cell anemia

Reference Values

Males: 65-150%

Females

<50 years: 50-150%

≥50 years: 65-150%

Newborn infants have normal or near-normal free protein S antigen (≥50%), although total protein S antigen is usually below the adult reference range. There are insufficient data concerning protein S activity in normal neonates, infants, and children; but normal or near-normal activity (≥50%) probably is present by age 3 to 6 months.

Interpretation

In type I and type III congenital deficiency, free protein S antigen is decreased, and protein S functional activity is similarly decreased. In type II congenital (dysfunctional) protein S deficiency, total and free protein S antigen levels are normal, but functional activity is decreased.

 

Patients with acquired free protein S deficiency associated with inflammation-related increase of C4b-binding protein typically have decreased free protein S antigen and protein S activity with normal (or elevated) total protein S antigen. Acquired protein S deficiency is of uncertain clinical hemostatic significance and is associated with a variety of conditions.

 

Elevated protein S levels are of uncertain clinical significance.

Day(s) Performed

Monday through Friday

Report Available

1 to 4 days

Specimen Retention Time

7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

85306

LOINC Code Information

Test ID Test Order Name Order LOINC Value
SFX Protein S Activity, P 27822-6

 

Result ID Test Result Name Result LOINC Value
SFX Protein S Activity, P 27822-6

Forms

If not ordering electronically, complete, print, and send an Coagulation Test Request (T753) with the specimen.