Apparent decrease of "inhibition" in the dilution curve system with the increase of anticoagulation. A paradox that is against the presence of inhibitors in coumarin treated patients.

The apparent "inhibition" found in coumarin plasma by means of the dilution curve system seems to decrease with the increase of anticoagulation. Three groups of anticoagulated patients with a P/N prothrombin time ratio of less than 1.8, between 1.8 and 2.3 and over 2.3, showed an "inhibition" of 1.6, 1.1 and 0.9 conventional units, respectively. An inverse correlation was found to exist between Thrombotest clotting times, P/N ratio, antigen/activity ratios on one side and inhibition units on the other side. These findings do not confirm the presence of "inhibitors" in coumarin treated patients.