Summary
We have attempted to exploit the Ca2+ -dependent stability of factor VIII in producing factor VIII concentrates of higher yield. Plasma levels of ionised calcium were increased in two ways: (a) whole blood collection into half-strength citrate CPD anticoagulant, leading to free Ca2+ levels of ca 120 µM and (b) apheresis collection of plasma which was then recalcified to free Ca2+ levels
of ca 300 µM under heparin cover. Coagulation factor concentrates were prepared using model versions of our industrial scale manufacturing methods. Factor VIII yield was increased through low citrate collection. This did not compromise factor IX yield or thrombogenic potential. Use of recalcified heparinised plasma did not lead to any improvement in factor VIII yield and resulted in a marked drop in factor IX recovery, possibly from interference by
heparin of factor IX binding in ion-exchange chromatography. The benefits accruable through the use of half-strength citrate CPD anticoagulant support the continued evaluation of this preservative in large scale blood collection and fractionation. The deleterious effects of heparin in charge-mediated plasma fractionations may pose serious difficulties in harvesting vitamin K dependent factors.
