External validation of IOTA simple descriptors and simple rules for classifying adnexal masses.

Objective: To assess the diagnostic performance of a three-step strategy proposed by the International Ovarian Tumor Analysis (IOTA) Group for discriminating between benign and malignant adnexal masses.

Methods: This was a prospective observational study, performed at two tertiary-care university hospitals, of women diagnosed with an adnexal mass on transvaginal or transabdominal ultrasound between December 2012 and December 2014. Women were scheduled for an ultrasound evaluation, which was initially performed by non-expert examiners. The examiner had to classify the mass using 'simple descriptors' (first step) and, if not possible, using 'simple rules' (second step). For inconclusive masses, an expert examiner classified the mass according to their subjective impression (third step). Masses were managed expectantly, with serial follow-up examinations, or surgically, according to ultrasound findings and clinical symptoms. Histology was used as the reference standard. Masses that were managed expectantly with at least 1 year of follow-up were considered as benign for analytical purposes. Women with less than 1 year of follow-up were not included in the study.

Results: Six hundred and sixty-six women were included (median age, 41 (range, 18-81) years) of whom 514 were premenopausal and 152 were postmenopausal. Based on the three-step strategy, 362 women had surgical removal of the mass (53 malignant and 309 benign), 71 masses resolved spontaneously and 233 persisted. Four hundred and forty-eight (67.3%) of 666 masses could be classified using simple descriptors and, of the 218 that could not, 147 (67.4%) were classified using simple rules. Of the remaining 71 masses, the expert examiner classified 45 as benign, 12 as malignant and 14 as uncertain. Overall sensitivity, specificity, positive likelihood ratio and negative likelihood ratio of the three-step strategy were 94.3%, 94.9%, 18.6 and 0.06, respectively.

Conclusion: The IOTA three-step strategy, based on the sequential use of simple descriptors, simple rules and expert evaluation, performs well for classifying adnexal masses as benign or malignant. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.