Inter country analysis of breast density classification using visual grading. Analysis of mammographic breast density using visual grading

Purpose: 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 inter-country MBD expectations and assessment approaches are associated with differences in MBD assessment. Methods: Twenty American Board of Radiology (ABR) examiners and 24 United Kingdom (UK) practitioners using the 4th edition BI-RADS® lexicon assessed 40 mammogram cases of 20 women. Twenty-six Royal Australian and New Zealand College of Radiologists (RANZCR) registered radiologists also assessed the same cases. Inter-observer correlation and agreement were assessed using a Spearman’s correlation (ρ) and weighted Kappa (Kw) 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); RANZCR radiologists and UK practitioners (ρ = 0.958)]. ABR and RANZCR radiologists demonstrated slight agreement [Kw = 0.10; 95% CI = -1.13 - 0.43] while ABR and UK practitioners showed a fair agreement [Kw = 0.25; 95% CI = -0.42 - 0.61], and an almost perfect agreement was observed between RANZCR radiologists and UK practitioners [Kw = 0.95; 95% CI = 0.91 - 0.97]. Conclusion: Findings demonstrate wide international and inter-observer variability in MBD assessment. This level of variability underscores the need for automation and standardisation of MBD assessment. Keywords: Breast density, inter-observer agreement, visual assessment methods