Ordering Guidance

Consider ordering in patients to aid in distinguishing between congenital thrombotic thrombocytopenic purpura (TTP) and acquired autoimmune TTP.

Specimen Required

Patient Preparation:

Fasting: 8 hours, preferred

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

Submission Container/Tube: Polypropylene plastic vial

Specimen Volume: 1 mL plasma

Collection Instructions:

1. Specimen must be collected prior to 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 into a separate plastic vial, leaving 0.25 mL in the bottom of centrifuged vial.

5. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, below -40° C.

Specimen Stability Information: Frozen 21 months

Additional Information:

1. Double-centrifuged specimen is critical for accurate results.

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