Objectives: To evaluate the diagnostic performances of ultrasound score (US), CA 125, menopausal status, risk of malignancy index (RMI)— in differentiating between benign and borderline or malignant ovarian tumors.
Material and Method: Women with ovarian masses who were scheduled to have elective surgery at the Department of Obstetrics and Gynecology, BMA Medical College and Vajira Hospital between May 1999 and December 2001 were included in the study. Ultrasonographic study and CA 125 were examined preoperatively. The RMI was obtained from the ultrasound score, CA 125, and menopausal status. The diagnostic values of each parameter and the RMI were determined.
Results: From 175 women, 35 women (20%) had malignant ovarian tumors. RMI yielded better diagnostic performance to differentiate between benign and borderline or malignant ovarian tumors than US score, CA125, and menopausal status in respective order. The optimal RMI to predict malignancy was 0.135 with the sensitivity of 88.6% (95% CI; 81.1%-96.1%), specificity of 90.7% (95% CI; 83.9%-97.6%), positive and negative predictive value of 70.5% (95% CI; 59.7%-81.2%) and 97.0% (95% CI; 92.9%-100.0%) respectively.
Conclusion: RMI yielded better diagnostic performance than the individual parameter of ultrasound score, CA 125, or menopausal status in differentiation of benign from borderline or malignant ovarian tumors.

Keywords: Risk of malignancy index, Ultrasound score, CA 125, Menopausal status, Ovarian tumor