Free Protein S Antigen; Protein S Antigen, Total and Free; Protein S, Free and Total Antigen; S Protein Antigen; Total Protein S Antigen
Test ID
PSTF
General Information
Useful for
Investigation of patients with a history of thrombosis
If this test result is decreased, then total plasma protein S antigen (PST) will be performed at an additional charge
Specimen Type
Citrated Plasma
Specimen Requirements
Light-blue top (3.2% sodium citrate)
Specimen Collection / Processing Instructions
MUST PROCESS WITHIN 4 HOURS OF COLLECTION Platelet poor Coag Citrate Specimen processing: 1. Gently invert tube 2-3 times prior to placing in Centrifuge 2. Centrifuge Citrate whole blood at 4500 rpm for 10 minutes 3. Carefully pipette plasma, avoiding the platelet/buffy coat into a plastic vial 4. Centrifuge plasma at 4500 rpm for 10 minutes 5. Pipette the plasma to a plastic vial, leaving the bottom 0.25 mL undisturbed 6. Freeze plasma immediately and transport frozen.
Additional Processing Details
0.5 mL
Stability
Frozen: 14 days
Unacceptable Specimen Conditions
Gross hemolysis
Gross lipemia
Gross icterus
Limitations
Protein S total antigen results are potentially affected by:
Heparin (unfractionated or low-molecular-weight) >4 U/mL
Hemoglobin >2 g/L
Bilirubin >100 mg/L
Rheumatoid factor >300 IU/mL may lead to an overestimation of the result
Antirabbit antibodies: certain subjects may have aberrant results
Lipemic specimen may lead to an overestimation
Free protein S antigen results are potentially affected by:
Heparin (unfractionated or low-molecular-weight) >4 U/mL
Hemoglobin >200 mg/dL
Bilirubin >25 mg/dL
Triglycerides >1500 mg/dL
Platelets >10
Rheumatoid factor >900 IU/mL
Factor V Leiden variant (APC-R)
Methodology
PSF, PST: Latex Immunoassay (LIA)
Estimated TAT
1-3 days
Testing Schedule
Monday-Friday
Test Includes
Protein S Antigen, Free
CPT Code(s)
85306
Reference Range
Demographic
Free Protein S Antigen (%)
Total Protein S Antigen (%)
Males
65 - 160
80 - 160
Females: < 50 years
50 - 160
70 - 160
Females: ≥ 50 years
65 - 160
80 - 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.
