title: Misclassification of Breast Imaging Reporting and Data System (BI-RADS) Mammographic Density and Implications for Breast Density Reporting Legislation.
abstract: USA states have begun legislating mammographic breast density reporting to women, requiring that women undergoing screening mammography who have dense breast tissue (Breast Imaging Reporting and Data System [BI-RADS] density c or d) receive written notification of their breast density; however, the impact that misclassification of breast density will have on this reporting remains unclear. The aim of this study was to assess reproducibility of the four-category BI-RADS density measure and examine its relationship with a continuous measure of percent density. We enrolled 19 radiologists, experienced in breast imaging, from a single integrated health care system. Radiologists interpreted 341 screening mammograms at two points in time 6 months apart. We assessed intra- and interobserver agreement in radiologists'; interpretations of BI-RADS density and explored whether agreement depended upon radiologist characteristics. We examined the relationship between BI-RADS density and percent density in a subset of 282 examinations. Intraradiologist agreement was moderate to substantial, with kappa varying across radiologists from 0.50 to 0.81 (mean = 0.69, 95% CI [0.63, 0.73]). Intraradiologist agreement was higher for radiologists with ≥10 years experience interpreting mammograms (difference in mean kappa = 0.10, 95% CI [0.01, 0.24]). Interradiologist agreement varied widely across radiologist pairs from slight to substantial, with kappa ranging from 0.02 to 0.72 (mean = 0.46, 95% CI [0.36, 0.55]). Of 145 examinations interpreted as "nondense" (BI-RADS density a or b) by the majority of radiologists, 82.8% were interpreted as "dense" (BI-RADS density c or d) by at least one radiologist. Of 187 examinations interpreted as "dense" by the majority of radiologists, 47.1% were interpreted as "nondense" by at least one radiologist. While the examinations of almost half of the women in our study were interpreted clinically as having BI-RADS density c or d, only about 10% of examinations had percent density >50%. Our results suggest that breast density reporting based on a single BI-RADS density interpretation may be misleading due to high interradiologist variability and a lack of correspondence between BI-RADS density and percent density.
authors.affiliation: Department of Economics, Applied Statistics, and International Business, New Mexico State University, Las Cruces, New Mexico.
authors.forename: Charlotte C
authors.initials: CC
authors.lastname: Gard
authors.affiliation: Group Health Research Institute, Group Health Cooperative, Seattle, Washington.
authors.forename: Erin J
authors.initials: EJ
authors.lastname: Aiello Bowles
authors.affiliation: Group Health Research Institute, Group Health Cooperative, Seattle, Washington.|Department of Public Health Sciences, UC Davis School of Medicine, Davis, California.
authors.forename: Diana L
authors.initials: DL
authors.lastname: Miglioretti
authors.affiliation: Division of Cancer Control and Population Sciences, Behavioral Research Program, National Cancer Institute, Bethesda, Maryland.
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Taplin
authors.affiliation: Group Health Research Institute, Group Health Cooperative, Seattle, Washington.|RAND Corporation, Santa Monica, California.
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Rutter
mesh_terms: D001940:Breast / Q000473:pathology; D000071060:Breast Density; D001943:Breast Neoplasms / Q000145:classification / Q000000981:diagnostic imaging* / Q000473:pathology*; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000002:abnormalities*; D015588:Observer Variation; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000592:standards*; D014481:United States
keywords: BI-RADS density; breast density reporting legislation; intra- and interradiologist agreement; misclassification; percent density