Laboratory Medicine Program

Factor XI Activity
(Factor 11)

Clinical Decription:
Factor XI is one of the contact factors and a serine protease. Low levels of factor XI (25%) are required for normal hemostasis. Deficiency of FXI is an unpredictable bleeding disorder commonly found in individuals of Ashkenazi descent.

Method: Optical Clot Detection; Siemens Sysmex CS-5100

Component Tests Used: n/a

Reference Ranges Used:
0.62 - 1.35 IU/mL

Specimen Type: Citrated plasma
Collected In: 3.2% Sodium Citrate
Volume: 1.0 mL (minimum: 1.0 mL)

Shipping: Send frozen on dry ice.

Special Instructions: Patient should be fasting, if possible. Anticoagulants should be held for a requisite amount of time prior to testing to ensure no anticoagulant effect on the plasma. The specimen must be double-centrifuged to obtain a platelet-poor plasma specimen (Plt <10x10E9/L): 1. Immediately centrifuge specimen at 1500xG for 10 minutes. 2. Separate the plasma from the platelet/buffy coat and transfer into a clean plastic tube. 3. Centrifuge the separated plasma at 1500xG for 10 minutes. 4. Transfer 1.0 to 2.0 mL of the double-centrifuged plasma into a clean plastic tube, leaving approx. 200 uL for discard. 5. Freeze plasma aliquot immediately for storage. Maintain frozen for shipping and handling.

Testing Schedule(s): Monday through Friday 0900-1500 hrs.

Turnaround Time: 1 day

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For more information, call 416.340.5227 or 1.866.865.5227

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