|Test Information||In this assay, FVIII activity is determined by utilizing a chromogenic substrate. FVIII in the sample is activated by thrombin and, in the presence of FIXa, phospholipids and calcium, activates FX. The initial rate of hydrolysis of a p-nitroanilide substrate specific for FXa is proportional to the FVIII activity.
In general, results should be similar to that found with the one-stage FVIII clotting assay. The chromogenic assay is not affected by lupus anticoagulants, heparins or direct thrombin inhibitors, and has been recommended by some as preferable for the measurement of high FVIII levels. Discrepancies between the one-stage and chromogenic assays are found in some patients with mild and moderate hemophilia A, influenced by the site of the hemophilia causative mutation.
|Additional Test Information||Normal Range: 45-180%, effective 10/1/12|
|Sample Requirements||Whole Blood: 3.2% Sodium Citrated (blue top) OR
|Requested Volume||Two 5 ml 3.2 sodium citrated (blue top) tubes as whole blood OR
Frozen plasma in 4 X 1mL aliquots in plastic tubes
|Minimum Volume or Pediatric volume||Frozen Plasma: at least 0.5ml in 2 plastic tubes.|
|Sample Information||Whole blood is preferred for testing but if it is not possible to send whole blood tubes TO ARRIVE HERE WITHIN 2 HOURS of collection then send frozen plasma. To prepare plasma centrifuge blue top tubes at 1500g for 15 minutes and remove the plasma and centrifuge a second time at 1500g for an additional 15 minutes. Aliquot approximately 1 ml of plasma into 4 plastic tubes, and freeze.|
|Shipping Information||Whole Blood: Send at ambient temperature (18-25C) and must be received within the lab in less than or equal to 3 hours after collection.
Frozen Plasma: send on dry ice
Send samples to:
For additional information, please see Ordering Information
|Requisition Form||RFT- Hemostasis Reference Laboratory|
|Test Schedule||Monday – Friday|
|Turn around Time (analytic time)||3 Business Days|
|Report/ Results||Fax number required to receive report|
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