Ordering Guidance

This test is for factor XI inhibitors only. If the presence or type of inhibitor is unknown, first order APROL / Prolonged Clot Time Profile, Plasma, except for patients with known hemophilia A or B. When screening studies are needed for patients with known hemophilia A or B, order 8INHE / Factor VIII Inhibitor Evaluation, Plasma; or 9INHE / Factor IX Inhibitor Evaluation, Plasma; respectively.

Shipping Instructions

Send all vials in the same shipping container.

Necessary Information

Specimen Required

Specimen Type: Platelet-poor plasma

Patient Preparation:

1. Patient should not be receiving anticoagulant treatment (eg, warfarin, heparin). If not possible for medical reasons, note on request.

 a. If medically feasible, for 4 to 6 hours before specimen collection, do not administer intravenous heparin.

 b. If medically feasible, for 10 to 14 days before specimen collection, do not administer subcutaneous heparin or warfarin.

2. Patient should not be receiving fibrinolytic agents (streptokinase, urokinase, tissue plasminogen activator [tPA]).

3. It is recommended that specimens be collected pretransfusion. If patient has been transfused, a specimen should not be collected for 48 hours.

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Polypropylene plastic vials

Specimen Volume: 3 mL Platelet-poor plasma in 3 plastic vials, each containing 1 mL

Collection Instructions:

1. Specimen must be collected prior to factor replacement therapy.

2. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing.

3. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.

4. Aliquot plasma (1-2 mL per aliquot) into 3 separate plastic vials, leaving 0.25 mL in the bottom of centrifuged vial.

5. Immediately freeze plasma at -20° C or, ideally, at -40° C or below.

Additional Information:

1. A double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

2. Each coagulation assay requested should have its own vial.