Intercountry analysis of breast density classification using visual grading

Objective: Disagreement in mammographic breast density (MBD) assessment can impact breast cancer risk stratification, choices of further breast cancer screening intervals and pathways. This study examines whether intercountry MBD expectations and assessment approaches are associated with differences in MBD assessment. Methods: 20 American Board of Radiology (ABR) examiners and 24 UK practitioners using the 4th edition BI-RADS® lexicon assessed 40 mammogram cases of 20 females. 26 Royal Australian and New Zealand College of Radiologists (RANZCR) registered radiologists also assessed the same cases. Interobserver correlation and agreement were assessed using Spearman's correlation (r) and weighted kappa (k_w), respectively. Results: Strong positive correlation was observed between the study cohorts on a binary scale (1-2 vs 3-4) [ABR examiners and RANZCR radiologists (ρ=0.950); ABR examiners and UK practitioners (ρ=0.940); and RANZCR radiologists and UK practitioners (ρ=0.958)]. ABR and RANZCR radiologists demonstrated slight agreement [k_w50.10; 95% confidence interval (CI)521.13-0.43], whereas ABR and UK practitioners showed a fair agreement [k_w50.25; 95% CI520.42-0.61], and an almost perfect agreement was observed between RANZCR radiologists and UK practitioners [k_w50.95; 95% CI50.91-0.97]. Conclusion: Findings demonstrate wide international and interobserver variability in MBD assessment. This level of variability underscores the need for automation and standardization of MBD assessment. Advances in knowledge: Intercountry analysis of MBD assessment shows variations, with less variation on the binary scale than on the 4-point scale. With this level of variation, automation and standardization of MBD assessment becomes more appropriate.