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.

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.