Serum CA 125 levels in patients with endometriosis: changes in CA 125 levels during menstruation

We investigated serum CA 125 levels in 120 patients with benign gynecologic disease, and examined variations in CA 125 levels during the menstrual cycle in six normally cycling women. CA 125 levels were elevated transiently during menstruation, suggesting that blood samples taken during menstruation can give a false-positive result. Whereas the CA 125 values during the nonmenstrual part of the cycle were significantly higher in the patients with adenomyosis and advanced endometriosis (stages III and IV) than in those with a normal pelvis, there was no difference between the patients with mild endometriosis (stages I and II) and the normal-pelvis group. CA 125 levels during menstruation were significantly elevated, not only in women with adenomyosis and advanced endometriosis, but also in those with mild endometriosis, compared with those with a normal pelvis. These data suggest that the measurement of serum CA 125 during menstruation may increase the rate of detection of endometriosis over that in studies done during other phases of the cycle.