CA 125 Relatively Specific for Diagnosing Endometriosis


Am Fam Physician. 2017 Jan 15;95(2):122.

Clinical Question

Is serum cancer antigen (CA) 125 an accurate noninvasive test for diagnosing endometriosis in symptomatic women?

Bottom Line

For women with symptoms suggestive of endometriosis, serum CA 125 is a relatively specific (93%) and noninvasive test. It can be used to make a presumptive diagnosis in cases for which a medical management approach is being considered without having to perform a (diagnostic standard) laparoscopic procedure to confirm. At minimum, pelvic ultrasonography to assess for other conditions (ovarian cancer or uterine fibroids) that can raise CA 125 levels is needed. CA 125 is not a sensitive test for endometriosis (52%), and therefore not helpful in ruling out the disease. Approximately one-half of the women with histologically proven endometriosis have normal CA 125 levels. (Level of Evidence = 1a –)


This is a well-designed meta-analysis of 22 observational studies (16 cohort and six case-control; N = 3,626 women) to assess the accuracy of CA 125 as a noninvasive diagnostic test for endometriosis. The standard for diagnosis of endometriosis is histological, requiring an invasive procedure. The authors calculated pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio. They considered different cutoff values for CA 125 results and performed multiple other subgroup analyses, including disease stage (1 and 2 vs. 3 and 4). Quantitative meta-analysis included 14 studies (n = 2,920 women) using a cutoff of at least 30 units per mL as a positive result. The pooled sensitivity was 52% (95% confidence interval [CI], 38% to 66%) and pooled specificity was 93% (95% CI, 89% to 95%). Although CA 125 showed higher sensitivity 63% (95% CI, 42% to 77%) when disease severity was limited to advanced disease, it was still not enough to recommend using the test to rule out disease.

Study design: Meta-analysis (other)

Funding source: Self-funded or unfunded

Setting: Various (meta-analysis)

Reference: Hirsch M, Duffy J, Davis CJ, Nieves Plana M, Khan KS; International Collaboration to Harmonise Outcomes and Measures for Endometriosis. Diagnostic accuracy of cancer antigen 125 for endometriosis: a systematic review and meta-analysis. BJOG. 2016;123(11):1761–1768.

POEMs (patient-oriented evidence that matters) are provided by EssentialEvidence Plus, a point-of-care clinical decision support system published by Wiley-Blackwell. For more information, please see http://www.essentialevidenceplus.com. Copyright Wiley-Blackwell. Used with permission.

For definitions of levels of evidence used in POEMs, see http://www.essentialevidenceplus.com/product/ebm_loe.cfm?show=oxford.

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This series is coordinated by Sumi Sexton, MD, Associate Deputy Editor.

A collection of POEMs published in AFP is available at https://www.aafp.org/afp/poems.



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