No abstract

Safety from transmission of infections through plasma-derived clotting factor concentrates is assured by improved donor screening, serological testing of individual donations and direct viral testing of small plasma pools. Modern viral-inactivation techniques are highly effective. Recombinant concentrates stabilized in human albumin are being superaeded by those with other stabilizers. Recently reported discrepancies between estimates of concentrate potency from in vitro assays versus in vivo recovery, depending upon type of assay and reference standard used, are not fully resolved.

Factor VIII inhibitor levels were measured on 261 occasions in 76 hemophilia-A inhibitor patients before and after prothrombin complex concentrate infusion at 13 treatment centers. A rise in inhibitor level to at least twice the pretreatment value occurred in 35 treatment episodes (13.5%), in 27 patients (36%). In 16 patients (21%), such an anamnestic immune response occurred with the first treatment. Factors predisposing to anamnestic responses may include patient idiosyncrasy, low pretreatment inhibitor levels, and exposure to concentrate over several days.

SummarySix brands of normal reference plasma produced in the United States, with assigned assay values for factor VIII and IX and, in four instances, ristocetin cofactor and von Willebrand antigen, were assayed in nine coagulation laboratories in academic institutions in the same country. Differences in mean assays of reference plasmas, as a percent of labelled potency, were significant and were greater than differences among laboratories. Standard methods of assigning potency to commercial reference plasmas are recommended.