The patient should not be on anticoagulant therapy

Lt blue Sodium citrate (NaCit) - 2.7mL x 3

• Do not draw from an arm with a heparin lock or heparinized catheter
• Immediatley following collection, mix sample thoroughly by gentle inverting 8 - 10 times, to prevent clotting

1. Centrifuge for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells.
2. Deliver to a plastic transport tube, cap, and recentifuge for 10 minutes.
3. Use a second plastic pipette to remove plasma, staying clear of the platelets at the bottom of the tube.
4. Transfer 2 mL of plasma into three (3) separate Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp) labelled as Na cit plasma
5. Freeze immediately

Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp) x 3

Frozen (preferred) – 30 days

Ambient – 4 hours

Refrigerated – NO

The factor V inhibitor (Bethesda titer) assay is performed using a prothrombin time-based system, using thromboplastin reagent.6 Serial dilutions are made of patient plasma with veronal buffered saline, then mixed with normal plasma containing close to 100% factor V activity, and are then incubated for two hours. A PT-based factor V assay using factor V-depleted plasma substrate is then performed on these incubated mixtures. Results are compared to those of incubated normal plasma. One Bethesda unit is defined as the amount of factor V inhibitor that neutralized 0.5 IU of factor V in this system. The number of serial dilutions tested is based on the anticipated level of the inhibitor.

Prothrombin and APTT, sec

Factor V activity, % and Facator V inact assay, <0.8 Bethesda