title: Percentage density, Wolfe's and Tabár's mammographic patterns: agreement and association with risk factors for breast cancer.
abstract: BACKGROUND
  The purpose of this report was to classify mammograms according to four methods and to examine their agreement and their relationship to selected risk factors for breast cancer.
  
  
  METHODS
  Mammograms and epidemiological data were collected from 987 women, aged 55 to 71 years, attending the Norwegian Breast Cancer Screening Program. Two readers each classified the mammograms according to a quantitative method (Cumulus or Madena software) and one reader according to two qualitative methods (Wolfe and Tabár patterns). Mammograms classified in the reader-specific upper quartile of percentage density, Wolfe's P2 and DY patterns, or Tabár's IV and V patterns, were categorized as high-risk density patterns and the remaining mammograms as low-risk density patterns. We calculated intra-reader and inter-reader agreement and estimated prevalence odds ratios of having high-risk mammographic density patterns according to selected risk factors for breast cancer.
  
  
  RESULTS
  The Pearson correlation coefficient was 0.86 for the two quantitative density measurements. There was moderate agreement between the Wolfe and Tabár classifications (Kappa = 0.51; 95% confidence interval 0.46 to 0.56). Age at screening, number of children and body mass index (BMI) showed a statistically significant inverse relationship with high-risk density patterns for all four methods (all P < 0.05). After adjustment for percentage density, the Wolfe classification was not associated with any of the risk factors for breast cancer, whereas the association with number of children and BMI remained statistically significant for the Tabár classification. Adjustment for Wolfe or Tabár patterns did not alter the associations between these risk factors and percentage mammographic density.
  
  
  CONCLUSIONS
  The four assessments methods seem to capture the same overall associations with risk factors for breast cancer. Our results indicate that the quantitative methods convey additional information over the qualitative methods.
authors.affiliation: Institute of Community Medicine, University of Tromsø, Breivika, Norway. inger.gram@ism.uit.no
authors.forename: Inger T
authors.initials: IT
authors.lastname: Gram
authors.forename: Yngve
authors.initials: Y
authors.lastname: Bremnes
authors.forename: Giske
authors.initials: G
authors.lastname: Ursin
authors.forename: Gertraud
authors.initials: G
authors.lastname: Maskarinec
authors.forename: Nils
authors.initials: N
authors.lastname: Bjurstam
authors.forename: Eiliv
authors.initials: E
authors.lastname: Lund
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000473:pathology; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods*; D008403:Mass Screening; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D015203:Reproducibility of Results; D012307:Risk Factors