Retrospective analysis of suspicious pelvic masses using the Pelvic Mass Index (PMI) scoring system from 2007 to 2014

This study aims to validate the accuracy of the Pelvic Mass Index (PMI) by comparing it with Risk of Malignancy Index (RMI) in a large patient cohort.

This retrospective study used data of women with ovarian masses collected from 2007 to 2014, referred to the Pelvic Mass Clinic (PMC) at University Hospital of Wales in Cardiff. The locally developed PMI was used to triage patients for surgery, surveillance or discharge. Performance measures for PMI, RMI and CA125 are reported as sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), receiver operating characteristic (ROC) curves and area under the curve (AUC) for premenopausal and postmenopausal women alike.

PMI was calculated on 1468 patients of whom 497 underwent surgery, 176 (71.0%) were in the high risk group, 63 (68.0%) intermediate and 258 (23%) amongst low risk women. Compared to RMI, PMI had a higher sensitivity (90.4%) and NPV (96.9%) for the entire cohort, as well as in the premenopausal (88.9%; 97.6%) and postmenopausal (91.5%; 95.6%) subcategories. ROC curves indicated better performance in the total group (AUC 0.823 vs. 0.770) and the premenopausal group (AUC 0.847 vs. 0.728), though AUC in the postmenopausal group was similar (0.779 vs. 0.791) - likely due to increased specificity of CA125 after menopause. Histology revealed PMI significantly outperforms RMI in diagnosing malignancy, missing only 1 compared to 20 cancers.

The high sensitivity and NPV of PMI makes it a useful tool in triaging patients with suspicious ovarian masses.