Discrepancies in potency assessment of recombinant FVIII concentrates

Abstract

Summary. Results of assays of recombinant FVIII concentrates have been reviewed over a 10‐year period. Initially there was wide variability between laboratories but this was minimised by the development of standardised assay methodology, in particular the use of haemophilic plasma for pre‐dilution and 1% albumin in assay buffers. Using this standardised methodology and concentrate standards, there were no major diferences in potency between one‐stage, two‐stage, and chromogenic assays on the two full‐length recombinant FVIII concentrates. However, using a plasma standard, the chromogenic method gave much higher potencies than the one‐stage method on the same concentrates, and this explains a similar discrepancy found in patients' post‐infusion samples after injection of recombinant concentrates. It is suggested that concentrate standards be used for such post‐infusion samples in order to minimise this discrepancy.