title: Activation profiles of factor VIII in concentrates reflect one-stage/chromogenic potency discrepancies.
abstract: We have investigated the possibility that differences in the profile of factor VIII (FVIII) activation, by thrombin, may help to explain the one-stage/chromogenic potency discrepancies in two therapeutic concentrates. A Method M concentrate and a recombinant B-domain-deleted (B-DD) concentrate were found to have one-stage/chromogenic ratios of approximately 1.15 and 0.70, respectively, relative to the World Health Organization (WHO) 6th International Standard (IS) FVIII concentrate, whether pre-diluted in FVIII-deficient plasma or buffer (+/- von Willebrand factor, VWF). The activation of FVIII, by thrombin, was followed in a buffer medium (+/- VWF) and all three concentrates showed similar times to reach peak FVIII coagulation (FVIII:C) activity. However, despite the use of equivalent amounts of FVIII:C for all three concentrates, the B-DD concentrate reached a higher peak level and maintained higher FVIII:C compared with the WHO 6th IS throughout the incubation period, whereas the Method M concentrate reached a lower peak level and maintained lower FVIII:C throughout the incubation period. We propose that the higher levels of FVIII:C found with the B-DD concentrate and the lower levels with the Method M concentrate, following activation, may be reflected in the potencies obtained by the chromogenic method and may be consistent with one-stage/chromogenic ratios of < 1.0 and > 1.0 respectively.
authors.affiliation: Division of Haematology, National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, Hertfordshire EN6 3QG, UK. thubbard@nibsc.ac.uk
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Hubbard
authors.forename: Lynne J
authors.initials: LJ
authors.lastname: Weller
authors.forename: Sally A
authors.initials: SA
authors.lastname: Bevan
mesh_terms: D001780:Blood Coagulation Tests; D002863:Chromogenic Compounds / Q000378:metabolism; D003029:Coagulants / Q000494:pharmacology* / Q000592:standards; D016903:Drug Monitoring; D005169:Factor VIII / Q000378:metabolism*; D006801:Humans; D012015:Reference Standards; D013917:Thrombin / Q000494:pharmacology* / Q000592:standards
chemical_list: D002863:Chromogenic Compounds; D003029:Coagulants; D005169:Factor VIII; D013917:Thrombin