The Diagnostic Value of the CA125 and Ultrasound Combination for Endometriosis: A Retrospective Cohort Study

Background: Endometriosis affects an estimated 10% of women of reproductive age and is characterized by chronic pelvic pain, infertility, and an increased risk of ovarian cancer. Laparoscopy remains the diagnostic gold standard for endometriosis; however, this technique is an invasive procedure. Therefore, non-invasive alternatives, such as serum biomarkers (e.g., carbohydrate antigen 125 (CA125), carbohydrate antigen 199 (CA199), and human epididymis protein 4 (HE4)) and ultrasound, represent promising techniques but currently lack consistent accuracy. Thus, this study aimed to evaluate the diagnostic efficacy of CA125, HE4, and ultrasound, individually and in combination, for detecting endometriosis. Methods: A retrospective analysis was conducted involving 51 patients with endometriosis and 52 healthy controls. Serum levels of CA125 and HE4 were measured by chemiluminescence, and ultrasound examinations were performed. Diagnostic performance was evaluated using sensitivity, specificity, accuracy, and receiver operating characteristic (ROC) curves. Results: CA125 levels were significantly elevated in patients with endometriosis (1.90 ± 0.39, log10) compared to controls (1.06 ± 0.22, log10; p < 0.001), yielding an area under the curve (AUC) of 0.97 (95% confidence interval (CI): 0.94–1.00), with a sensitivity of 94.23% (95% CI: 0.87–1.01), specificity of 92.16% (95% CI: 0.85–1.00), positive predictive value (PPV) of 92.18% (95% CI: 0.85–1.00), negative predictive value (NPV) of 94.21% (95% CI: 0.87–1.01), and accuracy of 93.20% (95% CI: 0.88–0.98). In contrast, HE4 did not exhibit a significant difference (p = 0.156). Ultrasound demonstrated a sensitivity of 72.55% (95% CI: 0.60–0.85), a specificity of 100.00% (95% CI: 1.00–1.00), PPV of 100.00% (95% CI: 1.00–1.00), NPV of 78.79% (95% CI: 0.69–0.89), and an accuracy of 86.41% (95% CI: 0.80–0.93). Combining CA125 and ultrasound enhanced the diagnostic accuracy to 95.15% (95% CI: 0.91–1.00), achieving a sensitivity of 92.16% (95% CI: 0.85–1.00), PPV of 97.92% (95% CI: 0.94–1.02), NPV of 92.73% (95% CI: 0.86–1.00), and specificity of 98.08% (95% CI: 0.94–1.01) (AUC: 0.96, 95% CI: 0.92–1.00). Conclusions: Combining CA125 and ultrasound significantly improves the non-invasive diagnosis of endometriosis, providing high sensitivity and specificity. This approach may reduce the reliance on laparoscopy, thereby facilitating earlier intervention. However, as this is a small-scale retrospective cohort study, larger sample cohorts are required for future validation to confirm these findings.