BACKGROUND: The IOTA Simple Rules provide a standardized ultrasound description in order to correctly classify ovarian tumors as benign or malignant even among non - expert readers. Its high accuracy rate was noted in foreign studies but was never validated in the local setting. The IOTA inconclusive tumors that were either assumed to be malignant or referred to experts in other studies were separately addressed in this research.

GENERAL OBJECTIVE: To determine the accuracy of the IOTA Simple Rules to predict malignant ovarian tumors

MATERIALS AND METHODS: Subjects: Patients with ovarian tumors admitted for surgery with complete ultrasound records done at Women's Health Unit and those with histopathologic report from the Department of Pathology. Setting: Department of Obstetrics and Gynecology in a tertiary hospital from August 2015 to February 2017. Design: Cross-sectional Diagnostic Accuracy Test. Data Collection: After obtaining approval from the IRB and Office of the Medical Director, the ovarian tumors were tallied and categorized according to their IOTA classification and final histopathologic diagnoses. The sensitivity, specificity, positive and negative predictive values, and accuracy were obtained using a 2x2 table. The biopsy reports of the inconclusive tumors were also reviewed and the sonographic characteristics of those which turned out to be malignant were noted.

RESULTS: A total of 110 adnexal masses were included, with the IOTA Simple Rules applicable in 84.55% of cases. It produced an accuracy rate of 100%. Among the 17 inconclusive tumors, two proved to be truly malignant with the presence of only one papillarity in a borderline tumor and the complex appearance of a germ cell tumor.

CONCLUSION: The IOTA Simple Rules is an accurate preoperative diagnostic tool in predicting ovarian malignancy. Two malignant tumors were classified as inconclusive and their sonographic characteristic of only one papillarity and the complex appearance of these tumors may warrant malignancy.