What blood investigations are used to diagnose endometriosis?

From the Guidelines

Currently, there are no specific blood tests that can definitively diagnose endometriosis. Diagnosis of endometriosis primarily relies on laparoscopic surgery with histological confirmation, which remains the gold standard 1. However, some blood investigations may be used as part of the diagnostic workup to rule out other conditions or to assess markers that might suggest endometriosis.

Blood Investigations

• CA-125 (Cancer Antigen 125) is sometimes measured, as it can be elevated in some women with endometriosis, particularly in advanced stages, but it lacks sensitivity and specificity for diagnosis 1.
• Other inflammatory markers like C-reactive protein (CRP) and certain cytokines may be checked, but these are non-specific.
• Complete blood count (CBC) might be performed to check for anemia if there is heavy menstrual bleeding.
• Hormonal profiles including estrogen, progesterone, and sometimes anti-Müllerian hormone (AMH) levels may be assessed, especially if fertility concerns exist.

Limitations of Blood Tests

Research is ongoing into potential biomarkers such as microRNAs and specific proteins, but these remain investigational 1. Blood tests should always be interpreted alongside clinical symptoms and imaging findings, with definitive diagnosis requiring surgical visualization and tissue sampling.

Diagnostic Approach

The American College of Obstetricians and Gynecologists (ACOG) recommends that a histologic examination should be done to confirm the presence of endometrial lesions, especially those with a nonclassical appearance 1. Only an experienced surgeon familiar with the protean appearances of endometriosis should rely on visual inspection to make the diagnosis. Peritoneal biopsy may be used to diagnose questionable peritoneal lesions.

From the Research

Blood Investigations for Endometriosis Diagnosis

The following blood investigations are used to diagnose endometriosis:

• CA 125 assay: This is the most commonly used blood test for endometriosis diagnosis 2, 3, 4, 5, 6

Characteristics of CA 125 Assay

The CA 125 assay has the following characteristics:

• Elevated serum CA 125 concentrations are observed in women with cystic ovarian endometriosis and/or deeply infiltrating endometriosis 2, 4
• The sensitivity of CA 125 assay is low, ranging from 36% to 63% 2, 6
• The specificity of CA 125 assay is high, ranging from 87% to 93% 2, 6
• CA 125 assay performs well as a rule-in test, but a negative test cannot rule out endometriosis 6

Clinical Utility of CA 125 Assay

The clinical utility of CA 125 assay is as follows:

• CA 125 assay can be used to diagnose deeply infiltrating endometriosis with a sensitivity of 36% and a specificity of 87% 2
• CA 125 assay can be used to monitor the completeness of surgery and detect recurrence of endometriosis 2, 4
• CA 125 assay can be used as an additional parameter to diagnose endometriotic disease in patients with chronic pelvic pain 4