title: In vivo recovery of factor VIII: a comparison of one-stage and two-stage assay methods.
abstract: The recovery and half-life of VIII:C in the plasma of severely haemophilic patients was measured by one-stage and two-stage assays after injection of two Factor VIII concentrates (Hemofil, Hyland and Fraction I-O, Kabi). Plasma volumes were measured with an Evans' Blue technique, and both concentrates and post-infusion samples were measured against the same plasma standard. There was a highly significant difference in recoveries estimated by the two assay methods. The one-stage assays gave the most consistent results, in that the average recovery was 100%, whereas the two-stage assays gave only about 80% of the value expected from in vitro assays. There was no differences in recoveries between the two concentrates. The two-stage assays gave a slightly shorter half-life than the one-stage assays, and the half-life of Hemofil was also shorter than that of Fraction I-O.
mesh_terms: D001681:Biological Assay / Q000379:methods*; D005169:Factor VIII / Q000008:administration & dosage / Q000032:analysis*; D006207:Half-Life; D006467:Hemophilia A / Q000097:blood; D006801:Humans; D008297:Male
chemical_list: D005169:Factor VIII