Background: Ovarian tumour usually presents as adnexal mass but often it is difficult to differentiate between benign and malignant tumour. Several diagnostic modalities such as sonography and tumours markers have been evaluated in the past, but none have been established as an ultimate diagnostic tool individually. The development of a mathematical formula using a logistic model, incorporating menopausal status, the serum level of a glycoprotein called CA-125 and USG score has been described in the form of different malignancy indices. The purpose of this study was to evaluate the various risks of malignancy indices (RMI 1, 2, 3, and 4) in the pre-operative evaluation of adnexal masses especially to differentiate between benign and malignant masses. Another objective of the present study was to compare the four RMI with each other in terms of various statistical parameters like specificity and sensitivity.Methods: Women with adnexal masses who underwent surgical treatment were included in this study as histopathological examination was taken as gold standard to calculate the accuracy of RMI. The sensitivity, specificity and positive predictive value and negative predictive value of all the four RMI were calculated and data analyzed.Results: A total of 65 patients were included in the study. RMI 1,2,3,4 was calculated according to their formula. Sensitivity of RMI- 1, 2, 3 and 4 was calculated to be 63.63%, 77.27%, 63.63% and 77.27% respectively. Specificity of RMI- 1, 2, 3 and 4 was calculated to be 69.04%, 64.28%, 64.28% and 62.79% respectively.Conclusions: Risk of malignancy index is a good diagnostic tool to differentiate between benign and malignant pelvic masses. RMI- 2 and RMI-4 had maximum sensitivity while RMI-1 had maximum specificity. Overall RMI-2 appears to be the most accurate of all the four RMI
