Performance of IOTA Simple Rules, Simple Rules risk assessment, ADNEX model and O‐RADS in differentiating between benign and malignant adnexal lesions in North American women
Authors: Hiett A. K. , Sonek J. D. , Guy M. , Reid T. J. 
Published: September 2021

ABSTRACTObjectivesTo apply the International Ovarian Tumor Analysis (IOTA) Simple Rules (SR), the IOTA Simple Rules risk assessment (SRR), the IOTA Assessment of Different NEoplasias in the adneXa (ADNEX) model and the Ovarian‐Adnexal Reporting and Data System (O‐RADS) in the same cohort of North American patients and to compare their performance in preoperative discrimination between benign and malignant adnexal lesions.MethodsThis was a single‐center diagnostic accuracy study, performed between March 2018 and February 2021, which included 150 women with an adnexal lesion. Using the ADNEX model, lesions were classified prospectively, whereas the SR, SRR assessment and O‐RADS were applied retrospectively. Surgery with histological analysis was performed within 6 months of the ultrasound exam. Sensitivity and specificity were determined for each testing modality and the performance of the different modalities was compared.ResultsOf the 150 women, 110 (73.3%) had a benign ovarian tumor and 40 (26.7%) had a malignant tumor. The mean risk of malignancy generated by the ADNEX model without CA 125 was significantly higher in malignant vs benign lesions (63.3% vs 11.8%) and the area under the receiver‐operating‐characteristics curve (AUC) of the ADNEX model for differentiating between benign and malignant adnexal masses at the time of ultrasound examination was 0.937. The mean risk of malignancy generated by SRR assessment was also significantly higher in malignant vs benign lesions (74.1% vs 15.9%) and the AUC was 0.941. To compare the ADNEX model, SRR assessment and O‐RADS, the malignancy risk threshold was set at ≥ 10%. This cut‐off differentiates O‐RADS low‐risk categories (Category ≤ 3) from intermediate‐to‐high‐risk categories (Categories 4 and 5). At this cut‐off, the sensitivity of the ADNEX model was 97.5% (95% CI, 85.3%–99.9%) and the specificity was 63.6% (95% CI, 53.9%–72.4%), and, for the SRR model, the sensitivity was 100% (95% CI, 89.1%–100%) and the specificity was 51.8% (95% CI, 42.1%–61.4%). In the 113 cases to which the SR could be applied, the sensitivity was 100% (95% CI, 81.5%–100%) and the specificity was 95.6% (95% CI, 88.5%–98.6%). If the remaining 37 cases, which were inconclusive under SR, were designated ‘malignant’, the sensitivity remained at 100% but the specificity was reduced to 79.1% (95% CI, 70.1%–86.0%). The 150 cases fell into the following O‐RADS categories: 17 (11.3%) lesions in Category 2, 34 (22.7%) in Category 3, 66 (44.0%) in Category 4 and 33 (22.0%) in Category 5. There were no histologically proven malignant lesions in Category 2 or 3. There were 14 malignant lesions in Category 4 and 26 in Category 5. The sensitivity of O‐RADS using a malignancy risk threshold of ≥ 10% was 100% (95% CI, 89.1%–100.0%) and the specificity was 46.4% (95% CI, 36.9%–56.1%).ConclusionsWhen IOTA terms and techniques are used, the performance of IOTA models in a North American patient population is in line with published IOTA results in other populations. The IOTA SR, SRR assessment and ADNEX model and O‐RADS have similar sensitivity in the preoperative discrimination of malignant from benign pelvic tumors; however, the IOTA models have higher specificity and the algorithm does not require the use of magnetic resonance imaging. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.