Is There a Better Way to Diagnose Endometriosis?

Peter Kovacs, MD, PhD


October 20, 2016

Diagnostic Accuracy of Cancer Antigen 125 for Endometriosis: A Systematic Review and Meta-analysis

Hirsch M, Duffy J, Davis CJ, Nieves Plana M, Khan KS
BJOG. 2016;123:1761-1768


Endometriosis is defined as the presence of endometrial glands and stroma in extrauterine locations. It's typically present along the tubes, on the ovaries, or in the cul-de-sac over the uterosacral ligaments. It may affect up to 30%-40% of women.[1]

Endometriosis is suspected based on symptoms (dysmenorrhea, menorrhagia, chronic pelvic pain, infertility, etc.), imaging (homogeneous ovarian cysts), or physical findings (direct visualization of lesions in the posterior vaginal vault, nodularity behind the uterus, adnexal masses). It is diagnosed, however, based on histologic evaluation of tissue samples removed during surgery.[1]

Cancer antigen (CA) 125 is a glycoprotein produced by coelomic epithelium, and elevated levels are found in diseases involving the ovary, Fallopian tube, peritoneum, endometrium, and lung.[2] It is primarily used by oncologists to monitor treatment success with epithelial ovarian cancer, but elevated levels have been associated with endometriosis as well. Therefore, measuring CA 125 in cases when endometriosis is suspected could help to establish the diagnosis and could eliminate the need for surgical exploration.


Twenty-two studies involving 3626 patients in whom endometriosis was diagnosed surgically were included in the systematic review. Endometriosis was staged according to the American Fertility Society classification, and subgroup analysis was done based on mild (stage I-II) or advanced (stage III-IV) endometriosis.

Out of the 22 studies identified, ultimately 14 were included in the meta-analysis.

The predictive accuracy using a cut-off of 30 IU/mL was tested: Overall, sensitivity was 52.4% (95% confidence interval [CI], 37.9%-66.4%), while the specificity was 92.7% (95% CI, 89.4%-95.1%). In mild endometriosis, the sensitivity was 24.8% (95% CI, 18.8%-32.1%); while in stage III-IV cases, it was 63.1% (95% CI, 47.2%-76.5%).

On the basis of their findings, the authors concluded that CA 125 is a good test to rule in endometriosis, but a negative test is not enough to exclude endometriosis.


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