COMPARISON OF 6 COMMERCIAL PLASMA REFERENCES FOR FACTOR-VIII, FACTOR-IX AND VON-WILLEBRAND-FACTOR - ON BEHALF OF THE SUBCOMMITTEE FOR FACTOR-VIII AND IX OF THE SCIENTIFIC AND STANDARDIZATION COMMITTEE OF THE ISTH

Six brands of normal reference plasma produced in the United States, w ith assigned assay values for factor VIII and IX and, in four instance s, ristocetin cofactor and von Willebrand antigen, were assayed in nin e coagulation laboratories in academic institutions in the same countr y. Differences in mean assays of reference plasmas, as a percent of la belled potency, were significant and were greater than differences amo ng laboratories. Standard methods of assigning potency to commercial r eference plasmas an recommended.