Observer variability of Breast Imaging Reporting and Data System (BI-RADS) for breast ultrasound

Purpose To evaluate inter- and intra-observer variabilities in breast sonographic feature analysis and management, using the fourth edition of the Breast Imaging Reporting and Data System (BI-RADS). Materials and methods We included 136 patients with 150 breast lesions who underwent breast ultrasound (US) and ultrasound-guided core needle biopsy. A pathological diagnosis was available for all 150 lesions: 77 (51%) malignant and 73 (49%) benign. Four radiologists retrospectively reviewed sonographic images of lesions twice within an 8-week interval. The observers described each lesion, using BI-RADS descriptors and final assessment. Inter- and intra-observer variabilities were assessed with Cohen's kappa statistic. Positive predictive value and negative predictive value (NPV) for final assessment were also calculated. Results For inter-observer agreements for sonographic descriptors, substantial agreement for lesion calcification and final assessment (κ = 0.61 for both), moderate agreement for lesion shape, orientation, boundary, and posterior acoustic features (κ = 0.49, 0.56, 0.59, and 0.49, respectively), and fair agreement for lesion margin and echo pattern (κ = 0.33 and 0.37, respectively) were obtained. For intra-observer agreement, substantial to perfect agreement was found for almost all lesion descriptors and final assessments. NPV for final assessment category 3 was 95%. Positive predictive value (PPV) for final assessment categorized as 4 or 5 were as follows: category 4a, 26%; category 4b, 89%; category 4c, 90%; and category 5, 97%. Conclusion Because inter- and intra-observer agreement with the BI-RADS lexicon for US is good, the use of BI-RADS lexicon can provide accurate and consistent description and assessment for breast US.