Role of transvaginal ultrasound and serum CA-125 in predicting severity of endometriosis: A prospective observational study

Background: Accurate preoperative assessment of endometriosis severity may improve counselling, referral, and surgical planning. Objective: To evaluate transvaginal ultrasonography (TVS) and serum CA-125, individually and in combination, for predicting stage III–IV endometriosis. Methods: This prospective diagnostic-accuracy study included 150 women with clinically suspected endometriosis who underwent preoperative TVS, serum CA-125 estimation, and operative staging using the revised American Society for Reproductive Medicine classification. Diagnostic performance was assessed for a predefined high-severity TVS category, CA-125, and a combined model. Results: Operative staging identified stage III–IV disease in 91 women (60.7%). High-severity TVS showed 93.4% sensitivity and 76.3% specificity. Serum CA-125 at 37.55 U/mL yielded 86.8% sensitivity, 88.1% specificity, and an AUC of 0.931. The combined model achieved the highest discrimination (AUC 0.957), with 90.1% sensitivity, 91.5% specificity, 94.3% positive predictive value, and 90.7% accuracy. High-severity TVS, increasing CA-125, and greater pain severity were independent predictors of stage III–IV disease. Conclusion: Combining TVS with serum CA-125 improved preoperative prediction of moderate-to-severe endometriosis and may support surgical risk stratification.