CA 125 levels measured in different phases of the menstrual cycle in screening for endometriosis

Abstract

Objective: To examine variations in CA 125 levels during the three phases of the menstrual cycle in women with and without endometriosis.

Methods: One hundred infertile women were studied prospectively. CA 125 levels were measured during menses and during the follicular and luteal phases before diagnostic laparoscopy. Subjects were divided into four groups: no evidence of endometriosis (35 women), stage I endometriosis (30 women), stage II endometriosis (21 women), and stages III and IV endometriosis (14 women).

Results: In the endometriosis groups, there was a significant difference in the mean CA 125 levels drawn at menses and those drawn in the follicular phase. In patients with severe endometriosis, there was also a difference in the mean CA 125 levels drawn at menses and in the luteal phase. This finding led to the development of a screening test based on the ratio of CA 125 levels at menses to levels in the follicular phase. The test based on this ratio (with a cutoff of 1.5) had a sensitivity of 62.5% and specificity of 75%, compared with a sensitivity of 26.8% and specificity of 100% for the test based on a single CA 125 level drawn at menses (with a cutoff of 35 U/mL).

Conclusions: CA 125 levels during menses are elevated compared with those during the follicular phase in patients with endometriosis. Screening tests based on the relationship of multiple CA 125 levels taken throughout the menstrual cycle were more sensitive for detection of endometriosis than tests based on a single CA 125 level.