IMPROVED RECOGNITION OF B-DOMAIN DELETED FVIII IN PLASMA WITH A NEW COMMERCIALLY AVAILABLE
VISULIZE™ F8PLUS ANTIGEN KIT

Ran Ni, Paul Erb, Joanne Della Maestra, Denise Foulon, Karen M. Black, Hugh Hoogendoorn
Affinity Biologicals, Ancaster, Ontario, Canada

Background: The 1st generation of VisuLize Factor VIII Antigen Kit was found to under-recover a recombinant B-domain deleted (BDD) FVIII antigen (Xyntha®) relative to plasma FVIII. As BDD forms of FVIII are becoming the most administered replacement products in Hemophilia A, there is a need for a commercially available FVIII antigen kit to reliably measure these truncated forms in plasma, using a WHO-traceable, plasma-based calibrator.

Methods: The 1st generation ELISA (VisuLize Factor VIII Antigen Kit) was reoptimized to select for conditions that improved the recovery of BDD-FVIII (Xyntha). The resulting 2nd generation of VisuLize Factor VIII Antigen Plus (F8PLUS Antigen) Kit still uses a normal plasma calibrator and plasma controls.

Objective: To provide a research tool for harmonizing the quantification of recombinant full-length and BDD-FVIIIs relative to a plasma-based calibrator.