CA-125 concentration in serum and peritoneal fluid in patients with endometriosis - preliminary results

Cancer antigen 125 (CA-125), known as a biomarker for women genital tract malignancies, could be also useful in detecting and monitoring endometriosis. The aim of this study was to evaluate CA-125 in serum and peritoneal fluid (PF) as an indicator of endometriosis.

Fifty-six patients admitted to the First Department of Obstetrics and Gynaecology for diagnostic or therapeutic laparoscopy conducted for infertility, pelvic pain, suspected endometriosis or ovarian cysts entered the study. Those with laparoscopically confirmed endometriosis were assigned to group A, those without this condition to group B. Blood for CA-125 was taken prior to surgery, centrifuged and assayed in accordance with the manufacturer's instructions (VIDAS CA-125 II). Peritoneal fluid and an endometrial biopsy were taken during laparoscopy. Statistical comparisons were performed using Statistica 7.1.

Group A consisted of 44 women with laparoscopically confirmed diagnosis; 15 patients served as a control group. The mean value of CA-125 concentration in the endometriosis group was 33.98 U/ml, vs. 9.3 U/ml in the control group. The mean value of CA-125 in peritoneal fluid was 1241.88 U/ml in the non-endometriosis group versus 2640.23 U/ml in the study group; both results were statistically significant (p < 0.05). There was a significant correlation between the stage of endometriosis and CA-125 plasma concentration (R = 0.5993, p < 0.001). Cancer antigen 125 concentration in serum was a moderate predictor to distinguish between patients with and without endometriosis (AUC 0.794; 95% CI 0.668-0.921; p = 0.001).

Cancer antigen 125 is a well-known biomarker for endometriosis and helpful in daily clinical practice when endometriosis is suspected. The cut-off value in serum suggesting endometriosis with 68% sensitivity is 11 U/ml. This value is normal range for Ca-125 concentration.