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Factor XI Activity and Human Inhibitor
Test Code17854
CPT Codes
85270, 85335
Preferred Specimen
2 mL frozen platelet-poor plasma collected in (x2) 3.2% sodium citrate (light blue-top) tubes
Minimum Volume
1 mL (x2)
Instructions
Platelet poor plasma: Centrifuge light blue-top tube for 15 minutes at approximately 1500 x g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (< 10,000/mcL). Freeze immediately and ship on dry ice. Do not thaw.
Transport Container
Plastic screw-cap vials
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen -20°C: 14 days
Frozen -70°C: 1 year
Refrigerated: Unacceptable
Frozen -20°C: 14 days
Frozen -70°C: 1 year
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolyzed specimens
Methodology
Clot based, Bethesda Assay
Setup Schedule
Set up: Tues; Report available: 3 days
Reference Range
Factor XI Activity | 65-150 | %normal |
Factor XI Human Inhibitor | <0.4 | Bethesda unit |
Clinical Significance
Factor XI Inactivator assay issued to quantitate inhibitor present in patient sample. The Bethesda assay is the most common test for determination of circulating FXI inhibitor in plasma.
Performing Laboratory
Quest Diagnostics Nichols Inst San Juan Capistrano
33608 Ortega Highway
San Juan Capistrano, CA 92690-6130