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Test Code LAB491 Protein S Activity

Clinical Information

Second order testing for diagnosis of congenital or acquired protein S deficiency, for example, as an adjunct to initial testing based on results of free protein S antigen assay (PSAGF). Evaluating patients with a history of venous thromboembolism.

Synonym

  • PROTS
  • Protein S Functional
  • PS Functional
  • PS Activity

Specimen Required

Preferred Container/Tube: 3.2% Citrate Blue Top - 2.7 mL
Specimen Volume: 2.7 mL
Acceptable Container/Tube: 3.2% Citrate Blue Top - 1.8 mL
Specimen Volume: 1.8 mL
Platelet poor plasma (PPP):
Specimen Volume: 2 - 1 mL aliquots platelet poor plasma (PPP)
Specimen Minimum Volume: 1 - 1 mL aliquot platelet poor plasma (PPP)

Specimen Collection Information

For Outreach, other than OSU Patient Service Centers: Samples must be processed and received frozen/must remain frozen in transit. 

For sending frozen plasma specimens, process immediately upon receipt. Centrifuge capped specimen tube in accordance with CLSI H21, at a speed and time required to consistently produce platelet-poor plasma (PPP = platelet count <10 K/uL). Transfer PPP into plastic aliquot tubes, cap and freeze. DO NOT transport until specimens are completely frozen.

Specimen Stability Information

Ambient: 
     Whole blood: 1 hour
      Platelet poor plasma: 4 hours
Frozen: 
      Platelet poor plasma: PPP removed from the cells and frozen at -20°C or ideally -70°C.

Rejected Due To

  • Ambient specimens >4 hours old
  • Clotted specimens
  • Underfilled or overfilled tube
  • Hemolysis

Reference Values

0-4 days: 12-60 % Activity
5-29 days: 22-78 % Activity
30-89 days: 33-93 % Activity
90-179 days: 54-118 % Activity
180-365 days: 55-119 % Activity
1-5 years: 53-173 % Activity
6-10 years: 55-155 % Activity
11-16 years: 65-138 % Activity
17+ years: 50-168 % Activity

Cautions

This test is not indicated in patients receiving warfarin (coumadin) therapy.

Method Description

Clotting assay based on the cofactor activity of protein S which enhances the anticoagulant action of activated protein C. This enhancement is reflected by the prolongation of the clotting time of a system enriched with factor Va which is a physiological substrate for activated protein C.

Performing Lab

Clinical Lab UH

Day(s) Performed

Monday through Friday (excludes OSU holidays)

Report Available

Same day/1 day

Reporting Name

Protein S Activity

CPT Code Information

85305

LOINC Code Information

27822-6