title: Standardization of factor VII/activated factor VII measurement in plasma of patients treated with recombinant factor activated VII.
abstract: To improve the standardization of the factor VII clotting activity (FVII:C) assay in patients treated with recombinant activated factor VII (rFVIIa), we conducted a multicentre study on plasma samples from four patients with haemophilia A, before and at various times after injection of a single dose of rFVIIa. FVII:C and prothrombin time were measured with the methods and reagents routinely used in each laboratory. Strong inter-laboratory variability of FVII:C values was found. The main source of variability was the type of thromboplastin. FVII:C values measured using rabbit thromboplastin were very close to activated factor VII clotting activity values (FVIIa:C) measured with a commercial assay (Staclot VIIa-TF). FVII:C values obtained with human placental thromboplastin were about three times lower than those obtained with rabbit and recombinant thromboplastins, and with the FVIIa:C assay. There was a good relationship between FVIIa:C and activated factor VII antigen values measured using a commercial immunoassay (Imubind FVIIa ELISA). In conclusion, rFVIIa at pharmacological concentrations can be easily monitored on the basis of FVII:C, using rabbit and probably also recombinant thromboplastin; equivalent results are obtained with a specific activated factor VII bioassay.
authors.affiliation: Department of Haematology, University Hospital of Lille, France. j-goudemand@chru-lille.fr
authors.forename: Jenny
authors.initials: J
authors.lastname: Goudemand
authors.forename: Claudine
authors.initials: C
authors.lastname: Caron
authors.forename: Marie
authors.initials: M
authors.lastname: Dreyfus
authors.forename: Pierre
authors.initials: P
authors.lastname: Sié
mesh_terms: D000818:Animals; D000941:Antigens / Q000032:analysis*; D005167:Factor VII / Q000032:analysis* / Q000276:immunology / Q000627:therapeutic use*; D015942:Factor VIIa / Q000032:analysis*; D005260:Female; D006467:Hemophilia A / Q000097:blood* / Q000188:drug therapy; D006801:Humans; D007202:Indicators and Reagents / Q000592:standards; D007518:Isoantibodies / Q000276:immunology; D010920:Placenta; D010949:Plasma; D011517:Prothrombin Time; D011817:Rabbits; D011994:Recombinant Proteins / Q000627:therapeutic use*; D012015:Reference Standards; D013925:Thromboplastin / Q000592:standards*
chemical_list: D000941:Antigens; D007202:Indicators and Reagents; D007518:Isoantibodies; D011994:Recombinant Proteins; C042580:factor VII clotting antigen; D005167:Factor VII; D013925:Thromboplastin; C103587:recombinant FVIIa; D015942:Factor VIIa