Factor VIII:C assay: influence of buffer components used in immunoaffinity chromatography for purification of factor...

A monoclonal antibody purified factor VIII concentrate containing FVIII/vWF complex has been assayed by one-stage clotting (CA) and chromogenic substrate (CSA) methods. The influences of potassium iodide (KI) and albumin in combination with predilution buffers, standards and storage of samples have been examined. These components are compared for their effect on FVIII potencies in final product and in-process controls. FVIII:C purified by immunoaffinity chromatography can not be measured reliably by CA or CSA, because of KI which interfere on the assay. Overall yield of FVIII, efficiency of IAC step and purity of FVIII can be determined by assaying the desalted samples.