DISCREPANCIES IN POTENCY ASSESSMENT OF RECOMBINANT FVIII CONCENTRATES

Results of assays of recombinant FVIII concentrates have been reviewed over a 10-year period. Initially there was wide variability between l aboratories 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 met hodology 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 s tandard, the chromogenic method gave much higher potencies than the on e-stage method on the same concentrates, and this explains a similar d iscrepancy found in patients' postinfusion samples after injection of recombinant concentrates. It is suggested that concentrate standards b e used for such post-infusion samples in order to minimise this discre pancy.