A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
Factor VIII Activity, Clotting
Message*Take to processing ASAP
Test Code
347
Alias/See Also
LAB306
CPT Codes
85240
Preferred Specimen
1 mL frozen platelet-poor plasma collected in 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL
Instructions
Platelet-poor plasma: Centrifuge light blue-top tube for 15 minutes at approximately 1500 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 and von Willebrand Factor studies.
Note: Storage of whole blood at refrigerated temperatures prior to processing may lead to cryoprecipitate formation and falsely low Factor VIII and von Willebrand Factor studies.
Transport Container
Transport tube
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days
Refrigerated: Unacceptable
Frozen: 30 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolysis • Received thawed
Methodology
Photometric Clot Detection
Setup Schedule
Sun-fri
Report Available
2-4 days
Limitations
Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: no effect; Heparin (UFH or LMWH): no effect to inhibitor pattern; Dabigatran or Argatroban (Thrombin Inhibitors): no effect to inhibitor pattern; Rivaroxaban or Apixaban (Factor Xa Inhibitors): no effect to inhibitor pattern.
Reference Range
50-180 % normal
Clinical Significance
This test is useful to evaluate a prolonged aPTT. The most common form of hemophilia is caused by a deficiency of Factor VIII. Hemophilia A is an X-linked disorder affecting between 1 in 5,000 to 10,000 males. Borderline low Factor VIII activity can be seen in female carriers of the defective Factor VIII gene. Typically this test is combined with other screening tests (eg. von Willebrand factor, Ristocetin Cofactor Activity) to evaluate for the presence von Willebrand disease.
Anticoagulant interference: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: no effect; Heparin (UFH or LMWH): no effect to inhibitor pattern; Dabigatran or Argatroban (Thrombin Inhibitors): no effect to inhibitor pattern; Rivaroxaban, Apixaban, Edoxaban (Factor Xa Inhibitors): no effect to inhibitor pattern. Other limitations: Factor VIII levels may be falsely low due to Lupus anticoagulant. A chromogenic Factor VIII activity is suggested. The presence of factor VIII antibodies (autoantibodies or antibodies resulting from replacement therapy) can result in low factor VIII levels. This test is NOT recommended for patients receiving emicizumab (ie. Hemilbra) as this therapy will yield falsely elevated values. Factor VIII is a positive acute phase reactant and levels will increase in a variety of clinical scenerios.
Anticoagulant interference: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: no effect; Heparin (UFH or LMWH): no effect to inhibitor pattern; Dabigatran or Argatroban (Thrombin Inhibitors): no effect to inhibitor pattern; Rivaroxaban, Apixaban, Edoxaban (Factor Xa Inhibitors): no effect to inhibitor pattern. Other limitations: Factor VIII levels may be falsely low due to Lupus anticoagulant. A chromogenic Factor VIII activity is suggested. The presence of factor VIII antibodies (autoantibodies or antibodies resulting from replacement therapy) can result in low factor VIII levels. This test is NOT recommended for patients receiving emicizumab (ie. Hemilbra) as this therapy will yield falsely elevated values. Factor VIII is a positive acute phase reactant and levels will increase in a variety of clinical scenerios.
Performing Laboratory
Quest Diagnostics Nichols Institute-San Juan Capistrano, CA |
33608 Ortega Highway |
San Juan Capistrano, CA 92675-2042 |