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Protein S Activity (LAB002082)
Test Mnemonic:

Protein S Activity

Specimen Requirements:

Routine venipuncture; discard 1st mL of blood by collecting a discard tube prior to collecting the blue-topped (3.2% sodium-citrate) tube.  For collections with butterfly blood collection sets, a discard tube should also be collected prior to collection of the blue top to ensure sufficient sample volume. Drawing a discard tube will displace the air from the blood collection set tubing to ensure proper blood draw volume. 


Blue-topped (3.2% sodium-citrate) tube

Minimum Volume:

1 mL of plasma

If delivery time is to be greater than 4 hours from time of draw, centrifuge the specimen for 15 minutes at 2000-2500g.
  1. Transfer plasma to 12x75 plastic tube.
  2. Cap tube and re-spin for 15 minutes at 2000-2500g.
  3. Remove from centrifuge without disturbing any platelet and/or cell pellets that might be on the botom or sides of the tube.
  4. Carefully transfer plasma into freezer tubes (plastic screw-top cryo-tubes) for testing or freezing to be sure to tape the patient's label onto the tube.
Specimen Preparation:

Fill within +/- 10% from stated capacity. Immediately after draw, gently invert 3-4 times




Ambient - 4 hours; Refrigerated - Unacceptable; Frozen -20oC - 8 hours, at -70oC - 6 months 

Causes for Rejection:
  • Clotted and hemolyzed plasma samples are unacceptable and must be redrawn.
  • Wrong tube or anticoagulant.
  • Wrong anticoagulant ratio (over or underfilled tubes).
  • Not centrifuged within the acceptable time after collection.
  • Whole blood or plasma refrigerated or placed on ice prior to testing.
  • Unlabeled.
  • Mislabeled.



Reference Range:

64 - 149%

Turnaround Time:

The hours of operation are Monday – Friday from 8:00 am to 4:00 pm with an expected TAT of 4 hours. STAT requests after business hours will be evaluated and handled by the on-call staff member.


Optical Clot-Based


CLS Specialty Lab

Click to view CLS Specialty Lab website  


Protein S Functional, Protein S Assay

CPT 4 Code:


When ordering tests for which Medicare or Medicaid reimbursement will be sought, physicians should only order tests that are medically necessary for the diagnosis or treatment of the patient. Components of the organ or disease panels may be ordered individually. The diagnostic information must substantiate all tests ordered and must be in the form of an ICD-10 code or its verbal equivalent.
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