Specimen Requirements

Container/Tube Type: 

Light Blue (Citrate)

Collection Information: 

Collect blood in a blue top tube, tube must be full for testing to be performed.

Transport Information: 

1. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.
2. Aliquot 1.0 mL of plasma into a plastic vial leaving 0.25 mL in the bottom of centrifuged vial.
3. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, at ≤-40° C.

Minimum Sample Volume: 

0.5 mL of citrate plasma

Remarks: 

1. If the patient is being treated with Coumadin, this should be noted. Coumadin will lower protein C.
2. Heparin (unfractionated or low molecular weight) 2 U/mL or more may interfere with this assay.

Unacceptable Conditions: 

Gross hemolysis, gross lipemia, gross icterus

Stability Comments: 

Platelet Poor Plasma
Centrifuge Specimen
Recommended centrifuge speed is 1500 x G for at least 15 minutes. Be careful that the tubes are evenly balanced when placing them into the centrifuge. When the centrifuge stops, carefully remove and rack tubes. Be aware that an unbalanced centrifugation, speed too slow, or centrifugation for too short of a spin time may all lead to an increase number of cells in the plasma which could contribute to a clotted specimen or erroneous results.
Remove Plasma
To remove plasma, start from the top, gently draw specimen into pipette as you go further down tube. Leaving approximately 0.5mL of plasma will insure that you do not disturb the buffy coat and cell layer.
Second Spin
Plasma separated from cells goes back into the centrifuge for a second spin. Balance and centrifuge the tubes. Failure to perform a second spin will result in plasma containing too many platelets which interfere with some coagulation testing and is a contributing factor for a clotted specimen.
Transfer Plasma to Aliquot Tubes
Pipette plasma from second spin tube into labeled aliquot tubes without disturbing the bottom 0.5mL.
Specimen Storage
Promptly freeze specimens after processing.