A new test system for evaluating the risk of thromboembolism in the use of hormonal contraceptives

Blood coagulation changes as well as an increased risk of thromboembolism brought about by oral contraceptive (OC) use have been documented. Unpublished research findings show that hypercoagulability can be determined by coagulation times in native (not anticoagulated) blood and plasma of patients with coronary heart disease and diabetes mellitus. 14 healthy women were studied before and 1-2 menstrual cycles after taking low-dose OCs in order to ascertain the effect of OC on coagulation by these test methods. Coagulation times were measured twice by a Haken coagulometer. Platelet-rich (5 minutes at 400 gm) and platelet-poor (10 minutes at 2000 gm) plasma was obtained by centrifugation. Recalcification times were determined by the citrate method. Cephaloplastin Dade was used a reagent for antiprothrombin time (aPTT). The Wilcoxon test was employed for analysis. Coagulation times were shortened in native platelet-rich plasma (from 521.9 + or - 227.9 to 378 + or - 145.7 seconds) and aPTT (from 30.2 + or - 1.7 to 28 + or - 1.7 seconds). The coagulation times were distinctly longer in native whole blood and platelet-rich plasma than the recalcification times in the present citrate systems. Most frequent coagulation parameter changes are the diminution of antithrombin III as well as the increase of platelet aggregation and fibrinogen. Platelet-mediated effect is evidenced by the rapid coagulation of platelet-rich plasma. The alteration of intrinsic plasmatic coagulation factors could account for the shortening of aPTT. The lack of demonstrable effect of OCs in the citrate system suggest significant coagulation physiology changes induced by citrate. These results indicate a certain activation of the coagulation system that seems to be mediated primarily by platelets.