“…Women were classified on the basis of demographic and clinical covariates known to be associated with the accuracy of mammography, 17,22,23 including age (in 5-year categories), breast density, and months since the most recent mammography. Facilities were classified according to academic affiliation, relative frequencies of screening and diagnostic imaging, interpretation of screening mammograms in batches of 10 or more, availability of interventional services (e.g., core biopsy), number of radiologists who specialized in breast imaging, interpretation of screening mammograms by more than one radiologist (i.e., double-reading), and the frequency of feedback about performance and the method used to review it.…”