Agreement of Gallbladder Reporting and Data System for Gallbladder Wall Thickening at Ultrasonography: A Multireader Validation Study

Abstract

ObjectiveTo evaluate the intra-reader and inter-reader agreement of ultrasound (US) gallbladder reporting and data system (GB-RADS) and validate the risk of malignancy in each GB-RADS category. Materials and MethodsThis retrospective study comprised consecutive patients with non-acute GWT who underwent US evaluation between January 2019 and December 2022. Three radiologists independently read the static US images and cine-loops for GB-RADS findings and assigned GB-RADS categories. The intra-observer (static images) and inter-observer (static images and cine-loops) agreement was calculated using kappa statistics and Krippendorff’s alpha. Another radiologist assigned a consensus GB-RADS category. The percentage of malignancy in each GB-RADS category was calculated. ResultsStatic US images of 414 patients (median age, 56 years; 288 women, benign=45.6% and malignant=54.4%) and cine-loops of 50 patients were read. There was weak to moderate intra-reader agreement for most GB-RADS findings and moderate intra-reader agreement for the GB-RADS category for all readers. On static images, the inter-reader agreement was acceptable for GB-RADS categories. On cine-loops, the inter-reader agreement for GB-RADS findings and categories was better than static images. The percentage of malignancy was 1.2%, 37%, 71.1%, and 89.1% in GB-RADS 2, 3, 4 and 5 categories. ConclusionGB-RADS has moderate intra-reader for GB-RADS categories. As originally proposed, the risk of malignancy is negligible in GB-RADS 2 category and highest in GB-RADS 5 category. However, the discriminatory performance of GB-RADS 3 and 4 categories is low. Larger multicenter studies with more readers must assess the reader agreement and validate the GB-RADS systems for wider clinical utilization.