title: Factor IX metal ion-dependent antigen assays for measurement of warfarin effect.
abstract: Factor IX metal ion-dependent antigen was assayed using monoclonal antibodies in 521 samples obtained after prothrombin time testing in patients treated with warfarin. Factor IX metal ion-dependent antigen was less than measured Factor IX clotting activity and less than total Factor IX antigen adsorbable to aluminium hydroxide, suggesting that the metal ion-dependent antigen assay measures a subpopulation of circulating Factor IX in patients treated with oral anticoagulants. There was a graded decrease of Factor IX metal ion-dependent antigen as prothrombin times increased in patient samples. In two hospitals, the median prothrombin times and Factor IX antigen levels were 19 and 20 seconds and 0.10 and 0.11 U/mL (kU/L), respectively. This study shows that immunoassays measure the biologic effect of warfarin and provide information that may supplement the prothrombin time test for patient monitoring. Factor IX metal ion-dependent antigen assays may be useful in efforts to standardize laboratory tests for warfarin effect.
mesh_terms: D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D005164:Factor IX / Q000032:analysis*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008670:Metals / Q000494:pharmacology; D008991:Monitoring, Physiologic / Q000379:methods*; D011517:Prothrombin Time; D014859:Warfarin / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D008670:Metals; D014859:Warfarin; D005164:Factor IX