Inter-observer variability in mammographic density assessment using Royal Australian and New Zealand College of Radiologists (RANZCR) synoptic scales

Introduction The aim of this study was to evaluate observer variability in mammographic density assessment as measured using the Royal Australian and New Zealand College of Radiologists (RANZCR) synoptic scales. Visual assessment of mammographic density by radiologists is commonly used in clinical practice; however, these assessments have been shown to be more subjective than quantitative methods. Methods The study included 40 cases of left cranial-caudal (CC) and mediolateral oblique (MLO) radiographs from 20 women. RANZCR-registered radiologists (n = 26) estimated mammographic breast density of the same images according to RANZCR synoptic scales 1-4. All images had their volumetric density classified using Volpara Density Grade (VDG) and Average Volumetric Breast Density percentage (AvBD%). Results The results showed that the radiologists sampled had specialized for 17.18 years (sd 12.03) and read 2072 (sd 2441) mammograms per year on average. Inter-observer agreement using RANZCR synoptic scales had an average Kappa of 0.360; (95% CI = 0.308-0.412) and a range of 0.078-0.499. Radiologists estimated percentage density was lower by 0.37 than VDG, with their mean being 2.18 and the mean VDG was 2.55 (Z = -3.873; P < 0.001). VDG and RANZCR showed a positive strong correlation (ρ = 0.898; P < 0.001). AvBD% and RANZCR also showed a positive strong correlation (ρ = 0.904; P < 0.001). Conclusion The inter-observer agreement with RANZCR synoptic scales was fair. Wide inter-observer variability was observed. Continued research on appropriate assessment methods for mammographic density assessment is required to avoid unnecessary variations.