A comparative study of the risk of malignancy index and the ovarian crescent sign for the diagnosis of invasive ovarian cancer

Objective To compare the value of the risk of malignancy index (RMI) and the ovarian crescent sign (OCS) in the diagnosis of ovarian malignancy. Methods This was a prospective observational study of women with ultrasonographic diagnosis of an ovarian cyst. The RMI was calculated in all cases using a previously published formula (RMI = U (ultrasound score) × M (menopausal status) × serum CA125 (kU/L)). A value > 200 was considered to be diagnostic of ovarian cancer. The OCS was defined as a rim of visible healthy ovarian tissue in the ipsilateral ovary. Its absence was taken as being diagnostic of invasive cancer. Results A total of 106 consecutive women were included in the study, of whom 92 (86.8%) had a benign ovarian tumor, five (4.7%) had borderline lesions and nine (8.5%) had an invasive ovarian cancer. The absence of an OCS diagnosed invasive ovarian cancer with a sensitivity of 100% (95% CI, 70–100%), specificity of 93% (95% CI, 86–96%), positive predictive value (PPV) of 56%, negative predictive value (NPV) of 100% and positive likelihood ratio (LR+) of 13.86 (95% CI, 6.79–28.29). This compared favorably with a sensitivity of 89% (95% CI, 57–98%), specificity of 92% (95% CI, 85–96%), PPV of 50%, NPV of 99% and LR+ of 10.78 (95% CI, 5.34–21.77), which were achieved using RMI > 200 (P < 0.01). Conclusions The RMI and the OCS are useful tests for discriminating between invasive and non-invasive ovarian tumors. The application of these tests in a sequential manner might improve the overall accuracy of ovarian cancer diagnosis. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.