Prospective external validation of IOTA three-step strategy to characterize and classify adnexal masses and retrospective assessment of an alternative two-step strategy using simple rules risk

OBJECTIVES:

To perform the external validation of the three-step strategy proposed by the International Ovarian Tumor Analysis Group to evaluate its diagnostic performance for classifying adnexal masses as benign or malignant, when ultrasound is performed by non-expert sonographers. As secondary objective, to assess the diagnostic performance of an alternative strategy using Simple Rules Risk as second step instead of Simple Rules.

METHODS:

Prospective observational study conducted from September 2015 to August 2017 in two university hospitals including a consecutive series of patients diagnosed as having an adnexal mass. All women were evaluated by ultrasound using the three-step strategy. Non-expert sonographers applied the first step (simple descriptors) and the second step (simple rules; if the mass could not be classified with the first step); an expert sonographer made the subjective assessment if the mass could not be classified with the first two steps. Reference standard was definitive histology after tumor removal when patients underwent surgery or at least twelve months of follow-up in those cases managed conservatively. The diagnostic performance of this strategy was estimated by calculating the sensitivity, specificity, positive and negative likelihood ratios and overall accuracy. Retrospectively, evaluation of an alternative strategy applying as a second step Simple Rules Risk to the masses not classified with Simple Descriptors, and classifying the lesions in low, intermediate and high risk. The diagnostic performance of this strategy was estimated by calculating the sensitivity and specificity assuming surgical intervention in intermediate or high risk lesions.

RESULTS:

Two hundred and eighty-three patients were included (median age: 48 years old). One hundred and sixty-five patients (58.3%) were premenopausal and 118 (41.7%) postmenopausal. Two hundred and sixteen women (76.3%) underwent surgical treatment (154 benign and 62 malignant) and 67 (23.7%) were managed with serial ultrasound scan for at least 12 months (all these masses were considered benign because no sonographic characteristic changes of malignancy were observed). Simple descriptors could be applied in 126 (44.5%) masses. Of the remaining 157 lesions, 112 (39.5%) could be characterized using simple rules. Of the remaining 45 (16.0%) masses, all could be classified by an expert sonographer. Therefore, 238 (84%) masses could be classified using the first two steps by non-expert sonographers. The diagnostic performance of the three-step strategy was as follows: sensitivity 95.1%; specificity 97.7%; positive likelihood ratio 42.1 and negative likelihood ratio 0.05. The diagnostic accuracy was 97.1%. With the strategy using Simple Rules Risk as a second step, of the 157 lesions not classified with Simple descriptors, 42, 38 and 77 presented low, intermediate and high risk respectively. Two hundred and ten women would have undergone surgical treatment. The diagnostic performance of this two-step strategy was sensitivity 98.8% and specificity 83.2%.

CONCLUSIONS:

The International Ovarian Tumor Analysis Group three-step system shows good accuracy for classifying adnexal lesions when used by non-expert sonographers. Another strategy by applying the simple rules risk calculator in the second step could also present good diagnostic performance by decreasing the number of surgical interventions and increasing the sensitivity of the strategy.

CITATION Ultrasound Obstet Gynecol. 2019 May;53(5):693-700. doi: 10.1002/uog.20163.