Use of CA125 fluctuation during the menstrual cycle as a tool in the clinical diagnosis of endometriosis; a preliminary report

Objective: To elucidate whether endometriosis can be diagnosed clinically by assessing the differences between serum CA125 levels during menstruation and during the rest of the menstrual cycle. Methods: The study was performed in 28 patients who underwent laparoscopy to check for pelvic causes of infertility. Patients with endometriosis were selected as the study group, and patients with normal laparoscopic findings functioned as the control group. Blood specimens were taken for CA125 determination during menstruation and during the rest of the menstrual cycle. Mean serum CA125 concentrations were compared by the two-sample t-test for between-group comparisons and the paired t-test for within-group comparisons. The receiver operating characteristic curve was applied to assess the usefulness of CA125 level changes during the menstrual cycle in the clinical diagnosis of endometriosis. Results: The mean CA125 concentrations of healthy women during menstruation and during the rest of the menstrual cycle were 12.2 and 10 U ml⁻¹, respectively. In this group, the mean CA125 concentration was an average of 22% higher during menstruation than during the rest of the menstrual cycle (P<0.001). The patients with endometriosis showed a similar pattern to that of normal women, but the levels differed by 198.3% in these patients (P<0.001). Mean CA125 concentrations of these patients during menstruation and in the rest of the cycle were 35.8 and 12 U ml⁻¹, respectively. The mean CA125 concentration during menstruation was significantly higher in patients with endometriosis than in normal women (P<0.001), but CA125 concentrations at other points in the menstrual cycle were found to be similar in both groups (P>0.05). ROC curve analyses set a cutoff of 83% (percentage increment of CA125 level during menstruation compared with that on days without menstrual bleeding), which gives a sensitivity of 93% and specificity of 92%, with a corresponding likelihood ratio of 11.3. Conclusions: It may be possible to diagnose endometriosis clinically by assessment of the differences in CA125 level during menstruation as against the remainder of the menstrual cycle.