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[Effect of substrate and diluent for factor VIII activity in highly purified factor VIII concentrate and patient
I Takahashi1, M Furuta, S Mizuno
1Japanese Red Cross Aichi Blood Center, Seto.
We studied the difference between congenital factor VIII deficient plasma and factor VIII immuno-depleted plasma on the effect of pre-dilution for factor VIII activity determined by the one-stage assay. When standard curves of one-stage assay for factor VIII: C by GEORGE KING factor VIII deficient plasma (frozen at -80 degrees C), BEHRING factor VIII deficient plasma (lyophilized), DADE factor VIII depleted plasma (lyophilized, von Willebrand factor antigen 0.2 U/ml) and DADE factor VIII depleted plasma (lyophilized, von Willebrand factor antigen 1.0 U/ml) were compared, the difference between the clotting times for 100% and 6.25% of activity in each reagent were 39.5, 29.5, 25.0, 23.0 seconds respectively. Potency values in concentrates without albumin or von Willebrand factor showed a discrepancy between pre-dilution in Owren-Koller buffer and pre-dilution in factor VIII deficient plasma. Potencies of those products pre-diluted in Owren-Koller buffer were 40-60% lower than potencies pre-diluted in factor VIII deficient plasma. These results showed substrate and pre-diluent must be chosen carefully for the accurate assay of factor VIII activity in vitro for the highly purified factor VIII concentrates.
We studied the difference between congenital factor VIII deficient plasma and factor VIII immuno-depleted plasma on the effect of pre-dilution for factor VIII activity determined by the one-stage assay. When standard curves of one-stage assay for factor VIII: C by GEORGE KING factor VIII deficient plasma (frozen at -80 degrees C), BEHRING factor VIII deficient plasma (lyophilized), DADE factor VIII depleted plasma (lyophilized, von Willebrand factor antigen 0.2 U/ml) and DADE factor VIII depleted plasma (lyophilized, von Willebrand factor antigen 1.0 U/ml) were compared, the difference between the clotting times for 100% and 6.25% of activity in each reagent were 39.5, 29.5, 25.0, 23.0 seconds respectively. Potency values in concentrates without albumin or von Willebrand factor showed a discrepancy between pre-dilution in Owren-Koller buffer and pre-dilution in factor VIII deficient plasma. Potencies of those products pre-diluted in Owren-Koller buffer were 40-60% lower than potencies pre-diluted in factor VIII deficient plasma. These results showed substrate and pre-diluent must be chosen carefully for the accurate assay of factor VIII activity in vitro for the highly purified factor VIII concentrates.