Test Directory

This test is used for confirmation and characterization of protein C deficiency.

Specimen Type: Citrated Platelet-Poor Plasma

Collection Container: 2 Light Blue Top (Sodium Citrate)

Desired Specimen Volume: 1 mL

Platelet-Poor Plasma Collection & Processing Instructions

1. Collect specimen in 2 light blue top (sodium citrate) tubes via venipuncture
   • When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternative anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes.
2.  The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood.

1. Perform platelet-poor plasma procedure.
2. Transfer 1 mL of platelet-poor plasma to a LabCorp PP transpak frozen purple tube.

Platelet-Poor Plasma Collection & Processing Instructions

Avoid warfarin (Coumadin®) therapy for two weeks and heparin therapy for two days prior to the test. Do not draw from an arm with a heparin lock or heparinized catheter.

Transport to the laboratory frozen. 

• Gross hemolysis
• Clotted specimen
• Frozen specimen thawed in transit
• Improper labeling

 See patient report.

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted.

Individuals with heterozygous PC deficiency may have low normal PC levels. Treatment with warfarin decreases the levels of vitamin K-dependent factors including PC. PC levels start to drop after six hours of warfarin treatment and do not regain pretreatment levels until generally two weeks after cessation of therapy. PC levels can become depleted as the result of activation of coagulation, limiting the utility of testing for congenital PC deficiency during the immediate convalescent period after a thrombotic event.

This procedure may be considered by Medicare and other carriers as investigational and, therefore, may not be payable as a covered benefit for patients.