Collect light blue top sodium citrate. 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 pipette plasma to a screw top plastic vial, centrifuge again, then pipette plasma (1 mL required) to a second screw top plastic vial. Indicate plasma from light blue on the transport tube, freeze immediately and ship on dry ice.

Patient Preparation:
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.