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Test Code FPSB Protein S Activity

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Light Blue Top Tube, 3.2% Sodium Citrate

Other Acceptable specimens: N/A

Note: 3.2% sodium citrate light blue top tubes must have 9 to 1 ratio of blood to anticoagulant. Overfilled/Underfilled tubes will be rejected.

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

Collect specimen per standard collection procedure and send to laboratory immediately. 

 

NOTE: Once each blue top tube is completely filled, gently invert the sample tube at least five times to ensure complete mixing of the contents.

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Collect specimen per standard collection procedure.
  • Once each blue top tube is completely filled, gently invert the sample tube at least five times to ensure complete mixing of the contents.
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature.
  • Carefully remove plasma from cells using a plastic transfer pipette avoiding buffy coat.
  • Aliquot removed plasma into 2 plastic tubes containing a minimum of 0.5 mL of specimen in each tube.
  • Plasma samples must then be frozen at -20oC.
  • Once solidly frozen, they must be shipped on dry ice. Samples that have thawed in transit will be rejected.

Collection Instructions

Collect specimen per standard laboratory collection procedures. 

 

NOTE: Once each blue top tube is completely filled, gently invert the sample tube at least five times to ensure complete mixing of the contents.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that have wrong ratio of blood to anticoagulant (under/overfilled), clotted or hemolyzed.

CPT Codes

85306

Volume

Preferred Volume: 2.0 mL

 

Minimum Volume: 1.0 mL

Specimen Stability

Storage Temperature

Stability

Room temperature

4 hours

Refrigerated

not acceptable

Frozen

30 days

Clinical Indications

Evaluating congenital protein S deficiency.

 

Investigation patients with a history of thrombosis.

Methodology

Clotting

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

STAT Turnaround Time: N/A

 

Routine Turnaround Time: 4 days

 

Testing Schedule:  Twice a week, Monday to Friday, 8 am to 3 pm

Synonyms/Keyword Search

Protein S, Protein S Functional

LOINC Codes

27822-6

Reference Values

 

Test

Age

Sex

Reference Range

Protein S Activity

All

All

63 - 118 %

Critical Values

Analyte

Unit

Low

High

Age

N/A

N/A

N/A

N/A

N/A

Additional Information

Protein S activity will be followed by reflexive protein S free antigen testing if the value is abnormally low. Additionally, if both protein S activity and protein S free antigen assays are low, Protein S total antigen testing will be performed.

 

In the immediate post-thrombotic period, a decreased Protein S value should not necessarily be interpreted as reflecting an underlying deficiency since the decrease may be due to consumption.

 

 

For inquiries regarding specimen requirements please call Coagulation Laboratory at 2-1315.

Last Review Date

03/09/2026

Test Components

Protein S Activity

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