Name: Protein S Ag, Free
Test Name: Protein S Ag, Free
Health Link Test Code: HCPSFREE
LIS Test Code: PSFREE
CPT Code(s): 85306
Days Performed: Mon-Fri, dayshift - day varies.
In-Lab Turnaround Time: 1 - 2 weeks.
Stat In-Lab Turnaround Time: Not available stat.
Patient must be off warfarin therapy for at least one week or on a stable dose of warfarin for at least one week.
Collection Container: Light blue top (3.2% NaCitrate)
Do NOT draw through a line containing heparin. The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. Tube must be allowed to fill completely.
Indicate if patient is receiving anticoagulant (warfarin/ Heparin/Vitamin K antagonist), direct thrombin inhibitor or fibrinolytic agent therapy.
Collection Volume: Full 3.5 mL tube
Pediatric Collection Volume: Pediatric tube filled to fill mark
4 hours on a spun tube
2 weeks at -20°C; 6 months at -70°C
Sample Analyzed: Plasma
Testing Volume: 1 mL
Pediatric Testing Volume: 0.3 mL
Centrifuge specimen to yield platelet poor plasma (platelet count should be less than 10 K/uL). Separate plasma and transfer to plastic tube or vial. Freeze plasma within 4 hours of collection at -20°C or below.
Outreach Specimen Processing:
Centrifuge specimen to yield platelet poor plasma (platelet count should be 10 K/µL or less). Separate plasma and transfer to labeled plastic tube and spin again. Transfer plasma from second spin to clean plastic labeled tube or vial. Indicate on tube "spun twice". Freeze plasma within 4 hours of collection at -20°C or below.
Transport whole blood specimen at room temperature to UWHC Hospital Laboratory within 4 hours of collection. See Specimen Processing for instructions if transport criteria are not met. Transport frozen plasma aliquot on dry ice to UWHC Hospital Laboratory.
Hemolyzed specimens, clotted specimens, partially filled tubes and whole blood specimens greater than 4 hours old when received by the laboratory are not acceptable. Specimens from patients who have not been off warfarin therapy for at least one week or on a stable dose of warfarin for at least one week are not acceptable.
|6 months and up||74-146 %NPP|
|6 months and up||55-124 %NPP|
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 C4bBP, 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.
Interpretation Type: Reference Interval
The presence of rheumatoid factor, anti-bovine albumin and/or anti-mouse antibodies in certain subjects may have a falsely elevated level of Free Protein S.
A clotting test for Protein S (functional portion) is also available (see Protein S Activity).
Free Protein S is not affected by Factor V Leiden mutation.