Confirmation and characterization of factor IX inhibitor

The patient should not be anticoagulated

Lt blue Sodium citrate (NaCit) - 2.7mL x 4

• Do not draw from an arm with a heparin lock or heparinized catheter.
• If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted.
• 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 4mL of plasma into two tubes (2 mL each). Use 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)

Frozen

Activated partial thromboplastin time (aPTT)-based system. Serial dilutions are made of patient plasma with veronal buffered saline, then mixed with normal plasma containing close to 100% factor IX activity and are then incubated for 2 hours. An aPTT-based factor IX assay using factor IX-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 IX inhibitor that neutralized 0.5 IU of factor IX in this system. The number of serial dilutions tested is based on the anticipated level of the inhibitor.

An interpretive report will be provided