title: Evaluation of mammographic density patterns: reproducibility and concordance among scales.
abstract: BACKGROUND
  Increased mammographic breast density is a moderate risk factor for breast cancer. Different scales have been proposed for classifying mammographic density. This study sought to assess intra-rater agreement for the most widely used scales (Wolfe, Tabár, BI-RADS and Boyd) and compare them in terms of classifying mammograms as high- or low-density.
  
  
  METHODS
  The study covered 3572 mammograms drawn from women included in the DDM-Spain study, carried-out in seven Spanish Autonomous Regions. Each mammogram was read by an expert radiologist and classified using the Wolfe, Tabár, BI-RADS and Boyd scales. In addition, 375 mammograms randomly selected were read a second time to estimate intra-rater agreement for each scale using the kappa statistic. Owing to the ordinal nature of the scales, weighted kappa was computed. The entire set of mammograms (3572) was used to calculate agreement among the different scales in classifying high/low-density patterns, with the kappa statistic being computed on a pair-wise basis. High density was defined as follows: percentage of dense tissue greater than 50% for the Boyd, "heterogeneously dense and extremely dense" categories for the BI-RADS, categories P2 and DY for the Wolfe, and categories IV and V for the Tabár scales.
  
  
  RESULTS
  There was good agreement between the first and second reading, with weighted kappa values of 0.84 for Wolfe, 0.71 for Tabár, 0.90 for BI-RADS, and 0.92 for Boyd scale. Furthermore, there was substantial agreement among the different scales in classifying high- versus low-density patterns. Agreement was almost perfect between the quantitative scales, Boyd and BI-RADS, and good for those based on the observed pattern, i.e., Tabár and Wolfe (kappa 0.81). Agreement was lower when comparing a pattern-based (Wolfe or Tabár) versus a quantitative-based (BI-RADS or Boyd) scale. Moreover, the Wolfe and Tabár scales classified more mammograms in the high-risk group, 46.61 and 37.32% respectively, while this percentage was lower for the quantitative scales (21.89% for BI-RADS and 21.86% for Boyd).
  
  
  CONCLUSIONS
  Visual scales of mammographic density show a high reproducibility when appropriate training is provided. Their ability to distinguish between high and low risk render them useful for routine use by breast cancer screening programs. Quantitative-based scales are more specific than pattern-based scales in classifying populations in the high-risk group.
authors.affiliation: National Centre for Epidemiology, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Macarena
authors.initials: M
authors.lastname: Garrido-Estepa
authors.forename: Francisco
authors.initials: F
authors.lastname: Ruiz-Perales
authors.forename: Josefa
authors.initials: J
authors.lastname: Miranda
authors.forename: Nieves
authors.initials: N
authors.lastname: Ascunce
authors.forename: Isabel
authors.initials: I
authors.lastname: González-Román
authors.forename: Carmen
authors.initials: C
authors.lastname: Sánchez-Contador
authors.forename: Carmen
authors.initials: C
authors.lastname: Santamariña
authors.forename: Pilar
authors.initials: P
authors.lastname: Moreo
authors.forename: Carmen
authors.initials: C
authors.lastname: Vidal
authors.forename: Mercé
authors.initials: M
authors.lastname: Peris
authors.forename: María P
authors.initials: MP
authors.lastname: Moreno
authors.forename: Jose A
authors.initials: JA
authors.lastname: Váquez-Carrete
authors.forename: Francisca
authors.initials: F
authors.lastname: Collado-García
authors.forename: Francisco
authors.initials: F
authors.lastname: Casanova
authors.forename: María
authors.initials: M
authors.lastname: Ederra
authors.forename: Dolores
authors.initials: D
authors.lastname: Salas
authors.forename: Marina
authors.initials: M
authors.lastname: Pollán
mesh_terms: D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D005260:Female; D006801:Humans; D008327:Mammography; D015588:Observer Variation; D011379:Prognosis; D015203:Reproducibility of Results; D014894:Weights and Measures