An in vivo assessment of factor VIII concentrates
G. Rock, P. Tittley and V. Fuller
Replacement therapy for patients with hemophilia A requires that a specific
dose of factor VIII be administered. Generally, these calculations involve
the use of the manufacturer's stated dose in an equation. We have assessed
factor VIII concentrates by in vitro techniques and found a considerable
discrepancy (35%) between the stated and the measured contents.
Confirmation of this discrepancy was obtained by in vivo assessment where
posttransfusion recoveries corresponded to the measured rather than the
stated contents of the vial. The half-disappearance time ranged from five
to eight hours. The data suggest that constant monitoring of factor VIII
preparations is necessary to ensure optimal treatment of patients with
hemophilia A and help to explain the recent efforts by the Office of
Biologics to achieve standardization.