PROTEIN C, FUNCTIONAL
Collect light blue top sodium citrate, tube must be filled. The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. Centrifuge and transfer 1 mL to a screw top plastic vial, indicate plasma from light blue on the transport tube. Ship on dry ice.
Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing. Do not draw from an arm with a heparin lock or heparinized catheter.
Protein C in plasma is activated by a specific enzyme (protein C activator) from copperhead snake venom (Agkistrodon contortrix). The amount of activated protein C is determined. The resulting activated PC (Protein Ca) is determined as the rate of hydrolysis of a chromogenic substrate in a kinetic test by measuring the increase in absorbance at 405 nm.
Confirmation and characterization of protein C deficiency