To assess the value of four kinds of risk of malignancy index (RMI) in the differential diagnosis of benign and malignant ovarian tumors.

We retrospectively analyzed the preoperative CA125 levels, menopausal status, ultrasound score, tumor size, and postoperative pathological data of 200 patients with ovarian tumors who were treated at Changzhou Second People's Hospital from October 2017 to October 2018. We used different calculation methods (RMI1, RMI2, RMI3, and RMI4) to calculate the RMI for distinguishing benign and malignant ovarian tumors, and the results were compared with pathology to evaluate their diagnostic value among different pathological tissue types and clinical stages. ROC curve analysis was performed to compare their diagnostic power with individual indicators and calculate their positive predictive value, negative predictive value, specificity, and sensitivity. The Cochran's Q test was used to compare the similarities and differences of the four methods (RMI1, RMI2, RMI3, and RMI4), and the Dunn's test (corrected by Bonferroni method) was used for pairwise comparison of the four methods.

The areas under the ROC curves of RMI1, RMI2, RMI3, and RMI4 were 0.859, 0.872, 0.866, 0.878, respectively. According to the ROC curve analysis, when the cutoff values of RMI1, RMI2, and RMI3 were all 100, and that of RMI4 was 200, the sensitivities were 77.5%, 82.6%, 80.0%, and 82.5%, and the specificities were 94.4%, 91.9%, 93.1%, and 93.1%, respectively. The positive predictive values were 77.5%, 71.7%, 74.4%, and 75.0%, respectively, which were higher than those of the original threshold. There were significant differences among the four RMI methods (χ²=8.333, P=0.04). After pairwise comparison, it was found that only RMI1 and RMI2 had a significant difference (P=0.028). RMI had a higher diagnostic rate for malignant epithelial ovarian tumors (71%, 77%, 71%, and 74%), and RMI2 had a higher diagnostic rate than the other three RMIs. However, RMI had a lower diagnostic rate for non-epithelial ovarian tumors (40% each). Among ovarian malignant tumors, the diagnosis rate for stage I lesions and borderline tumors was low.

The four RMIs have high specificity and positive predictive value for the diagnosis of benign and malignant ovarian tumors, but the sensitivity to non-epithelial tumors, borderline tumors, and early-stage ovarian tumors is low, and further improvement is needed.