Sign in →

Test Code PSTF Protein S Antigen, Plasma

Additional Codes

CNE Order Code: Protein S Ag - P

Reporting Name

Protein S Ag, P

Useful For

Investigation of patients with a history of thrombosis

Profile Information

Test ID Reporting Name Available Separately Always Performed
PSF Protein S Ag, Free, P No Yes

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
PST Protein S Ag, Total, P No No

Testing Algorithm

If free protein S antigen is decreased, then total plasma protein S antigen will be performed at an additional charge.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Plasma Na Cit


Specimen Required


Specimen Type: Platelet-poor plasma

Patient Preparation:

1. Patient should not be receiving anticoagulant treatment (eg, warfarin, heparin). Warfarin will lower protein S. If not possible for medical reasons, note on request.

 a. If medically feasible, for 4 to 6 hours before specimen collection, do not administer intravenous heparin.

 b. If medically feasible, for 10 to 14 days before specimen collection, do not administer subcutaneous heparin or warfarin.

2. Patient should not be receiving fibrinolytic agents (streptokinase, urokinase, tissue plasminogen activator [tPA]).

3. It is recommended that specimens be collected pretransfusion. If patient has been transfused, a specimen should not be collected for 48 hours.

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

Submission Container/Tube: Plastic vials (Polypropylene preferred)

Specimen Volume: 1 mL Platelet-poor plasma in 2 plastic vials, each containing 0.5 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 0.5 mL of plasma into 2 plastic vials, leaving 0.25 mL in the bottom of centrifuged vial.

4. Immediately freeze plasma (no longer than 4 hours after collection) at -20° C or, ideally at -40° C or below.

5. Send specimens in the same shipping container.

Additional Information: A double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.


Specimen Minimum Volume

Platelet-poor plasma: 0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma Na Cit Frozen 14 days

Reference Values

TOTAL

Males: 80-160%

Females:

<50 years: 70-160%

≥50 years: 80-160%

 

FREE

Males: 65-160%

Females:

<50 years: 50-160%

≥50 years: 65-160%

 

Normal, full-term infants or healthy premature infants may have decreased levels of total protein S (15-50%); but because of low levels of C4b-binding protein, free protein S may be normal or near the normal adult level (≥50%). Total protein S reaches adult levels by 90 to 180 days postnatal.*

 

*See Pediatric Hemostasis References section in Coagulation Guidelines for Specimen Handling and Processing

Day(s) Performed

Monday through Friday

CPT Code Information

85306-Free

85305-Total (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PSTF Protein S Ag, P 87557-5

 

Result ID Test Result Name Result LOINC Value
PSF Protein S Ag, Free, P 27821-8

Interpretation

Protein S values vary widely in the normal population and are age- and sex-dependent.

 

Table. Types of Heterozygous Protein S Deficiency

Type

Protein S antigen free

Protein S antigen total

Protein S activity

I

Low

Low

Low

II

Normal

Normal

Low

III

Low

Normal

Low

 

Protein S and C4b-binding protein (C4bBP) are coordinately regulated, and an increased total protein S antigen and low free protein S antigen most commonly reflect acute or chronic inflammation or illness with an associated increase in plasma C4bBP.

 

For patients in whom hereditary protein S deficiency is strongly suspected and the free plasma protein S antigen level is normal, consideration should be given to testing of free protein S activity, S_FX / Protein S Activity, Plasma, for detecting type II protein S deficiency (which is rare).

 

An increased total protein S antigen is of uncertain clinical significance because free protein S antigen levels are usually normal, in such situations. However, the total protein S antigen level may be helpful in distinguishing acquired versus congenital protein S deficiency. High normal or increased total protein S antigen and reduced free protein S antigen suggests acquired protein S deficiency, as may be seen in pregnancy or inflammation. In contrast, low normal or decreased total protein S antigen and reduced free protein S antigen suggests vitamin K deficiency or a warfarin (Coumadin) effect but also could reflect congenital protein S deficiency (type I or III).

 

Vitamin K deficiency, oral anticoagulant therapy, presence of liver disease, or disseminated intravascular coagulation/intravascular coagulation and fibrinolysis are common acquired causes of protein S deficiency, which is of uncertain significance when such conditions are present. Concomitant assay of coagulation factor II activity may be helpful in differentiating congenital protein S deficiency from oral anticoagulation effects, but supportive data are currently suboptimal.

 

Differentiation of congenital and acquired protein S deficiency requires clinical correlation and may require repeated laboratory study of the patient and selected family members in some instances. DNA-based testing may be helpful; see GNPRS / Protein S Deficiency, PROS1 Gene, Next-Generation Sequencing, Varies.

Report Available

1 to 3 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Method Name

PSF, PST: Latex Immunoassay (LIA)