Factor X antigen--factor X activity discrepancy in coumarin treated patients. No relationship with dilution curve

The plasma of 12 patients on coumarin medication was investigated with regard to factor X antigen, factor X activity, factor X antigen--factor X activity difference (delta) and dilution curve. The plasmas were divided into 3 groups according to the level of anticoagulation (under anticoagulated, normally anticoagulated, over anticoagulated). The average factor X antigen and the average factor X activity were 56.7, 53.0, 34.6 and 25.5, 20.1, 11.1%, respectively for the three groups of patients. The antigen-activity differences (delta) were 21.2, 22.5 and 23.5%, respectively. The degree of inhibition in conventional units was 2.6, 1.7 and 0.4 units for the three groups of patients, respectively. The decrease of "inhibition" with the increase of anticoagulation is not in agreement with the presence of similar levels of pre-factors or delta antigen-activity in the plasma of the three groups of patients. These data are against the presence of inhibitors in coumarin treated patients.