Inter-Reader Agreement of ATA Sonographic Risk in Thyroid Nodules with Bethesda Category III Indeterminate Cytology

Background: Substantial inter-observer variation has been documented in the recognition and description of specific sonographic features as well as for ATA sonographic risk (ASR). This raises the question if the risk stratification proposed by the ATA guidelines is reproducible and applicable for nodules with indeterminate cytology. The aim of the study was to determine the inter-reader agreement (IRR) among radiologists using the 2015 ASR stratification in indeterminate thyroid nodules. Methods: Three board certified radiologists who were blinded to clinical data and to each other, interpreted the ultrasound findings of 179 nodules that had Bethesda III cytology. The nodules were classified into high suspicion (HS), intermediate (IS), low (LS), very low (VLS). Echogenicity, composition, shape taller than wide, vascularity, type of margins, presence and type of calcifications were also described. Results: The majority consensus revealed that 28%, 27%, 39% and 5% were described as high, intermediate, low and very low ASR, respectively. The inter-reader agreement was near perfect (k 0.82 CI 95% (0.77–0.87)). Nodules were paired into a higher risk (HS + IS) and lower risk (LS + VLS) categories with substantial agreement (k 0.7) in both categories. Conclusion: A near perfect agreement among readers was observed when stratifying indeterminate cytology nodules for ASR.