PB1177 - Performance of FVIII deficient plasma with VWF in the activity measurement of FVIII replacement products in plasma samples using an OSC assay.

Background: Factor VIII (FVIII) replacement therapy is the standard of care for persons with hemophilia A. One-stage clotting (OSC) assays are commonly used to measure FVIII activity in plasma samples. FVIII depleted plasma, used as a substrate in OSC assays, may be deficient in von Willebrand Factor (VWF). FVIII depleted plasma with normal levels of VWF is a better alternative, mimicking congenital hemophilia A plasma.

Aims: To evaluate the recovered activity of six FVIII replacement products – ADVATE®, AFSTYLA®, ELOCTATE®, Jivi®, Novoeight®, & Wilate® – in plasma samples by an OSC assay using FVIII Deficient Plasma with VWF.

Methods: Each FVIII replacement product was reconstituted according to the manufacturer’s instruction and diluted with congenital FVIII deficient plasma to prepare seven levels of FVIII activities (0.05, 0.1, 0.2, 0.4, 0.6, 0.8 and 1.0 IU/mL) based on labeled potency. Five replicates of each level were measured on an IL ACL TOP 700 CTS analyzer freshly after preparation using HemosIL aPTT SynthASiL and Factor VIII Deficient Plasma with VWF (Precision BioLogic Inc.). Linear regression analysis of dose-dependent recoveries was performed.

Results: Using acceptance criteria of 100 ± 25% recovery, 5 out of 6 products across all levels were assayed accurately. Mean FVIII% recoveries across all levels of Advate, Eloctate, Jivi, Novoeight and Wilate were 93, 95, 101, 113 and 95% respectively. The percent recoveries of Afstyla, after x2 conversion, fell within the acceptance criteria for levels of ≥ 0.1 IU/mL but over-estimated at 149.76% at the lowest level of 0.05 IU/mL.

Conclusion(s): Factor VIII Deficient Plasma with VWF correctly supports quantification of FVIII activity in plasma samples containing Advate, Eloctate, Jivi, Novoeight and Wilate in the range of 0.05-1.0 IU/mL. Afstyla doses lower than 0.1 IU/mL were over-estimated by our assay.