Factor VIII Activity Chromogenic

Method Chromogenic
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
Frozen Plasma
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:

Bloodworks Northwest
Attn: Hemostasis Laboratory
921 Terry Ave
Seattle, WA 98104

For additional information, please see Ordering Information
Requisition Form RFT- Hemostasis Reference Laboratory
Transaction Code 3210-18
CPT Codes 85260
Test Schedule Monday - Friday
Turn around Time (analytic time) 3 Business Days
Report/ Results Fax number required to receive report