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Test Code PTSAFM Protein S Antigen, Plasma

Additional Codes



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 this test result 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

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.

Specimen Type: Platelet-poor plasma

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.
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

0.5 mL

Specimen Stability Information

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

Reference Values


Males: 80-160%


<50 years: 70-160%

≥50 years: 80-160%



Males: 65-160%


<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.

Day(s) Performed

Monday through Friday

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


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

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)

Secondary ID