Preoperative Risk Stratification of Adnexal Masses Using the International Ovarian Tumor Analysis (IOTA) Simple Rules and Risk of Malignancy Index (RMI) 2: A Prospective Diagnostic Study From a Tertiary Centre in Southern India.

OBJECTIVE: The objective of this study was to compare the diagnostic accuracy of International Ovarian Tumor Analysis (IOTA) Simple Rules with Risk of Malignancy Index 2 (RMI 2) for preoperative stratification of adnexal masses, and to assess the performance of serum CA-125 and handling inconclusive IOTA results, using histopathology as the reference standard. METHODS: A prospective diagnostic accuracy study was conducted at a tertiary care center in South India, enrolling 56 women aged ≥18 years with ultrasonographically detected adnexal masses scheduled for surgery. IOTA Simple Rules and RMI 2 scoring were applied preoperatively. All patients underwent surgical excision, and the final diagnosis was based on histopathology. Diagnostic metrics, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and area under the ROC curve (AUC), were calculated. Sensitivity analyses were performed for inconclusive IOTA cases, and statistical comparisons used DeLong and McNemar's tests. RESULTS: Of 56 cases, 11 (19.6%) were malignant and 45 (80.4%) benign. IOTA Simple Rules were conclusive in 52 (92.9%) cases. For conclusive IOTA, sensitivity was 90.9%, specificity 95.1%, PPV 83.3%, NPV 97.5%, accuracy 94.2%, and AUC 0.930. RMI 2 showed sensitivity 72.7%, specificity 97.8%, PPV 88.9%, NPV 93.6%, accuracy 92.9%, and AUC 0.853. Sensitivity analyses revealed robust NPV and accuracy with alternative coding of inconclusive IOTA results. CONCLUSION: IOTA Simple Rules provide superior sensitivity and comparable specificity compared to RMI 2, supporting their role as a safe and reliable first-line tool for preoperative risk stratification of adnexal masses in gynecologic practice.