Abstract Number: PB0584
Meeting: ISTH 2020 Congress
Background: Accurate measurement of factor VIII:C (FVIII) activity is a major concern in patients with hemophilia A. Extended half-life (EHL) FVIII products have been introduced for treatment of these patients, and it is important to understand how EHL-FVIII concentrates behave in the different one-stage coagulation assay (OSA), especially the different contents of phospholipids in APTT reagents.
Aims: To evaluate the influence of phospholipids on EHL-FVIII activity in OSA.
Methods: FVIII deficient plasma was spiked with 0.05-1.0 IU/mL of standard full-length (FL) FVIII
(FL-FVIII) and three EHL-FVIII concentrates (FL-FVIII-PEG, BDD-FVIII-Fc, and BDD single-chain [BDD-FVIII-SC]). APTT reagents were prepared at 50-300 mg/L of total phospholipids with ellagic acid as the activator. In addition, reagents containing variable composition of phospholipids were prepared by mixing of phosphatidylserine (PS; 0-70 mg/L) and phosphatidylcholine (PC; 70-0 mg/L) with constant concentration of phosphatidylethanolamine (PE; 30 mg/L) as PE is crucial for the assay. FVIII activity was calculated by each calibration curve using standard plasma on an automated blood coagulation analyzer.
Results: PS was essential to establish calibration curve for FVIII activity, and slope of the curve at low levels was steepening with increase of PC/PS ratio. Variations in the phospholipid concentration did not affect the activity of FL-FVIII, BDD-FVIII-Fc and BDD-FVIII-SC. In contrast, dilution of the phospholipids had a substantial influence on the activity of FL-FVIII-PEG at high levels where the apparent activity decreased. Composition of phospholipids with variable concentrations of PS and PC did not influence on activities of any FVIII products, when 10 mg/L of PS was present in the reagents.
Conclusions: Our data show that concentration of phospholipids influences on activity of FL-FVIII-PEG, and that compositions of PS and PC do not affect any EHL-FVIII products in OSA.
To cite this abstract in AMA style:Fujimori Y, Madoiwa S, Shinohara S, Kumano O, Arai N, Igari A, Wakui M, Murata M. Influence of Phospholipids on the Measurement of Extended Half-Life Factor VIII Activity in One-Stage Clotting Assay [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/influence-of-phospholipids-on-the-measurement-of-extended-half-life-factor-viii-activity-in-one-stage-clotting-assay/. Accessed October 1, 2023.
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