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Test Code LAB5503 Protein S Antigen, Plasma

Important Note

Mayo's test code: PSTF

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Reporting Name

Protein S Ag, P

Specimen Type

Plasma Na Cit


Specimen Required


Specimen Type: Platelet-poor plasma

Patient Preparation: Patient must not be receiving heparin or Coumadin. If the patient is being treated with Coumadin, this should be noted. Coumadin will lower protein S.

 

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

Submission Container/Tube: Plastic vials

Specimen Volume: 1 mL 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. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally  -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.


Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Specimen Stability Information

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

Specimen Minimum Volume

0.5 mL

Day(s) Performed

Monday through Friday

Specimen Retention Time

7 days

Report Available

1 to 3 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 newborn 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

Reflex Tests

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

Useful For

Investigation of patients with a history of thrombosis

Testing Algorithm

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

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

Profile Information

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

Supportive Data

A retrospective review of Mayo Special Coagulation Laboratory data found that of 584 patients tested sequentially, only 4 patients demonstrated a pattern of normal free protein S antigen with decreased total protein S antigen. Three of these patients were receiving oral anticoagulant therapy and 1 had liver disease. There were 8 patients with probable congenital protein S deficiency. Of this group, all had significantly reduced levels of free protein S antigen and normal or mildly reduced levels of total protein S antigen. We conclude that omission of routine measurement of total protein S antigen and substituting measurement of free protein S antigen with reflexive testing of total protein S antigen only for decreased free protein S antigen would not decrease clinical sensitivity of this assay system for detecting hereditary protein S deficiency.