Patient should not be on warfarin (coumadin) therapy for 2 weeks or heparin therapy for 2 days prior to the test. If the patient is currently on warfarin or heparin, this should be noted, as warfarin or heparin therapy can affect certain coagulation factors or assays, preclude their performance or cause spurious results.

Draw blood in a light blue sodium citrate tube (see coagulation collection instructions). Spin to separate and freeze 2.0 mL plasma in a screw-capped plastic vial. Label transport tube “plasma/lt blue” and contact lab for dry ice.