Factor VII during Warfarin Treatment

Using a one stage clotting assay and an antibody neutralization test, factor VII levels were measured in 91 healthy subjects and 46 patients on long term warfarin treatment. The mean factor VII levels in the healthy subjects were 130 % and 124 % of a reference plasma in the clotting and the antibody neutralizing assays respectively, and this difference was not statistically significant. In warfarin treated patients the values were 38 % and 51 % respectively, and the excess of the antibody neutralizing material, though small, was statistically significant (p < O.01). Factor MI levels in healthy subjects were analysed in men and women separately: in women there was an excess of clotting activity over antigenic activity, whereas no such excess was found in men. After a single small oral dose of warfarin in two male volunteers, both the clotting activity and antibody neutralizing activity were reduced, but the estimated antibody neutralizing activity always exceeded the clotting activity. In three patients (two men and one woman) starting long term warfarin treatment both biological and im‐munological activity were reduced in paralIel; in two out of three patients a slight excess of antibody neutralizing activity was present. These results suggest that PIVKA VII is present in small amounts in patients on long term oral anticoagulants.