Comparison of the factor IX levels in premenopausal and postmenopausal women.

Factor IX antigen levels are shown (median, interquartile range, and range); OC+ refers to oral contraceptive use both at the time of thrombosis and at the time of venipuncture; OC− refers to nonusers of oral contraceptives (both at the time of thrombosis and at the time of the venipuncture); premenop and postmenop refer to premenopausal and postmenopausal, respectively. Group 1: premenopausal patients using oral contraceptives (n = 30; median = 116 U/dL); group 2: premenopausal healthy controls using oral contraceptives (n = 47; median = 112 U/dL); group 3: premenopausal patients not using oral contraceptives (n = 40; median = 110 U/dL); group 4: premenopausal healthy controls not using oral contraceptives (n = 90; median = 91 U/dL); group 5: postmenopausal patients not using oral contraceptives (n = 60; median = 119 U/dL); group 6: postmenopausal controls not using oral contraceptives (n = 88; median = 105 U/dL).