PATIENTS WITH APC RESISTANCE COMPARED WITH THOSE WITH OTHER CLOTTING INHIBITOR DEFICIENCIES SHOW LATER ONSET OF VENOUS THROMBOSIS DURING ORAL CONTRACEPTION

The prevalence of deep vein thrombosis in female patients with antithr ombin III(AT III), protein C, or protein S deficiency who are on oral contraception has been compared with that of patients with activated p rotein C (APC) resistance. In the latter case the prevalence was lower (36.4%) than in the AT III deficiency group (71.4%) but similar to th at seen in the protein C and protein S group (25%). Furthermore, venou s thrombosis occurred with APC resistance much later than with AT III, protein C, or protein S defects. The time lag between onset of oral c ontraception and thrombosis (similar to 16 cycles) was not statistical ly different from that seen in a group of women who were known to have no antithrombin III, protein C, or protein S defects. It appears that as far as the interaction with oral contraception is concerned APC re sistance is a much less severe condition compared with other clotting inhibitor defects.