title: Assay of factor IX antigen using an enzyme immuno assay.
abstract: An Enzyme Linked immuno Sorbent Assay (ELISA) was developed for the measurement of factor IX:Ag. The results obtained in 90 control subjects, 56 hemophilia B patients and 40 patients under oral anticoagulant treatment were compared with factor IX:C and factor IX:Ag levels according to Electro Immuno-Assay (EIA). In healthy volunteers the mean factor IX:C level was 106.7 U/dl, the mean factor IX:Ag level was 96.8 U/dl according to EIA procedure and 101.5 U/dl according to ELISA method. Using ELISA, 10 hemophiliacs had no detectable antigen, and 13 had minute amounts of IX:Ag. All these patients are classified as B-. Among the others 21 had reduced antigen and are considered as BR and 12 had normal level of IX:Ag and are B+. Patients taking oral anticoagulants had not only a decreased factor IX:C level but also a reduced factor IX:Ag level which is always lower when using EIA procedure in the presence of EDTA than according to ELISA method.
mesh_terms: D000941:Antigens / Q000032:analysis*; D004306:Dose-Response Relationship, Immunologic; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005164:Factor IX / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male
chemical_list: D000941:Antigens; D005164:Factor IX