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 antithrombin III(AT III), protein C, or protein S deficiency who are on oral contraception has been compared with that of patients with activated protein 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 that seen in the protein C and protein S group (25%). Furthermore, venous thrombosis occurred with APC resistance much later than with AT III, protein C, or protein S defects. The time lag between onset of oral contraception and thrombosis (similar to 16 cycles) was not statistically 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 resistance is a much less severe condition compared with other clotting inhibitor defects.