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.

Patient Preparation:
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.