title: Inter- and intraradiologist variability in the BI-RADS assessment and breast density categories for screening mammograms.
abstract: OBJECTIVE
  The aim of this study was to evaluate reader variability in screening mammograms according to the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) assessment and breast density categories.
  
  
  METHODS
  A stratified random sample of 100 mammograms was selected from a population-based breast cancer screening programme in Barcelona, Spain: 13 histopathologically confirmed breast cancers and 51 with true-negative and 36 with false-positive results. 21 expert radiologists from radiological units of breast cancer screening programmes in Catalonia, Spain, reviewed the mammography images twice within a 6-month interval. The readers described each mammography using BI-RADS assessment and breast density categories. Inter- and intraradiologist agreement was assessed using percentage of concordance and the kappa (κ) statistic.
  
  
  RESULTS
  Fair interobserver agreement was observed for the BI-RADS assessment [κ=0.37, 95% confidence interval (CI) 0.36-0.38]. When the categories were collapsed in terms of whether additional evaluation was required (Categories III, 0, IV, V) or not (I and II), moderate agreement was found (κ=0.53, 95% CI 0.52-0.54). Intra-observer agreement for BI-RADS assessment was moderate using all categories (κ=0.53, 95% CI 0.50-0.55) and substantial on recall (κ=0.66, 95% CI 0.63-0.70). Regarding breast density, inter- and intraradiologist agreement was substantial (κ=0.73, 95% CI 0.72-0.74 and κ=0.69, 95% CI 0.68-0.70, respectively).
  
  
  CONCLUSIONS
  We observed a substantial intra-observer agreement in the BI-RADS assessment but only moderate interobserver agreement. Both inter- and intra-observer agreement in mammographic interpretation of breast density was substantial. Advances in knowledge Educational efforts should be made to decrease radiologists' variability in BI-RADS assessment interpretation in population-based breast screening programmes.
authors.affiliation: Servei d'Epidemiologia i Avaluació, Hospital del Mar, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Redondo
authors.forename: M
authors.initials: M
authors.lastname: Comas
authors.forename: F
authors.initials: F
authors.lastname: Macià
authors.forename: F
authors.initials: F
authors.lastname: Ferrer
authors.forename: C
authors.initials: C
authors.lastname: Murta-Nascimento
authors.forename: M T
authors.initials: MT
authors.lastname: Maristany
authors.forename: E
authors.initials: E
authors.lastname: Molins
authors.forename: M
authors.initials: M
authors.lastname: Sala
authors.forename: X
authors.initials: X
authors.lastname: Castells
mesh_terms: D000071060:Breast Density; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000002:abnormalities; D008327:Mammography / Q000592:standards*; D008875:Middle Aged; D015588:Observer Variation