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Factor VIII Activity, Clotting with Reflex to Chromogenic Method
Test Code70050
CPT Codes
85240
Includes
If Factor VIII Activity, Clotting is ≤20, then Factor VIII Activity, Chromogenic will be performed at an additional charge (CPT code(s): 85240).
Preferred Specimen
3 mL frozen plasma collected in a 3.2% sodium citrate (light blue-top) tube
Minimum Volume
1 mL
Instructions
Platelet-poor plasma: Centrifuge light blue-top tube 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.
Note: Storage of whole blood at refrigerated temperatures prior to processing may lead to cryoprecipitate formation and falsely low Factor VIII.
Note: Storage of whole blood at refrigerated temperatures prior to processing may lead to cryoprecipitate formation and falsely low Factor VIII.
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?)
Hemolysis • Received room temperature • Received refrigerated • Received thawed
Methodology
Photometric Clot Detection
Reflex: Chromogenic Assay
Setup Schedule
Set up: Wed, Sat; Report available: 1-5 days
Clinical Significance
In the presence of a suspected lupus anticoagulant, the one-stage appt based assay may yield false low FVIII values consistent with "haemophilia" whereas the chromogenic assay avoids lupus anticoagulant interference and yields accurate FVIII results.