Protein S Antigen, Free
| Label Mnemonic: | PSAF |
| Epic code: | LAB8982 |
| Order form: | Laboratory Requisition |
| Supply order: | Supply Order Form |
| Billing: | Billing Policies |
| CPT code: | 85306 |
Specimen(s):
Plasma
Collection Medium:
 |
| Light Blue top tube 2.7 mL (Na Citrate) |
Minimum:
Full draw, 2.7 mL light blue top tube
Rejection Criteria:
Short drawn tube, clot, traumatic tap (excessive hemolysis).
Testing
Schedule:
0800-1630 Monday, Wednesday and Friday. If you need results STAT, call Hematology resident (0800-1630, M-F) at 356-8628. All other times page the Pathology resident on-call at 3404.
Turn Around
Time:
1-3 days upon receipt in laboratory
Reference Range:
Females: 66-147%
Males: 73-139%
Interpretive Data:
Patients on warfarin may have decreased free protein S antigen concentrations. Warfarin therapy should be discontinued for at least two weeks prior to protein S testing. Decreased concentrations of free protein S antigen are also associated with liver disease, vitamin K deficiency, acute thrombosis, and DIC. Pregnancy, estrogen therapy, nephrotic syndrome, and inflammatory syndromes increase C4b binding protein concentrations, thus decreasing free protein S levels.
Methodology:
Immunoturbidimetric assay
Sample
Processing:
Double-centrifuge specimen to prepare platelet-free plasma.
Immediately centrifuge specimen at 3500 RPM for 12 minutes.
Using a plastic transfer pipette, carefully remove plasma from cells avoiding the platelet/buffy coat.
Place plasma into a labeled plastic tube.
Centrifuge plasma again at 3500 RPM for 12 minutes.
Remove the top of the plasma and place into a labeled plastic tube.
Freeze double-spun plasma within 4 hours of collection time at -20 degrees C or below.
Immediately centrifuge specimen at 3500 RPM for 12 minutes.
Using a plastic transfer pipette, carefully remove plasma from cells avoiding the platelet/buffy coat.
Place plasma into a labeled plastic tube.
Centrifuge plasma again at 3500 RPM for 12 minutes.
Remove the top of the plasma and place into a labeled plastic tube.
Freeze double-spun plasma within 4 hours of collection time at -20 degrees C or below.
Sample
Storage:
Freeze specimen immediately.
Transport
Instructions:
Place labeled specimen into zip-lock type biohazard bag; seal bag.
Place packing list into outside pocket of bag.
Place dry ice on top of specimen in Styrofoam container.
Samples received thawed will be cancelled.
Place packing list into outside pocket of bag.
Place dry ice on top of specimen in Styrofoam container.
Samples received thawed will be cancelled.
See Additional Information:
Impact of Common Anticoagulants on Coagulation Tests
Impact of Common Anticoagulants on Coagulation Tests