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Primary Source of Variation
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Underlying Sources of Variation
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Case Variation
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Breast density
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Breasts that are mammographically dense are associated with more false positives and false negatives42,65
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Hormone replacement therapy generally increases breast density.
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Menopause generally lowers breast density.
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Overweight women usually have less dense breasts.
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Breast density usually decreases with age.
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Breast cancer history
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Family history of breast cancer63
Previous biopsy
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Practice Variation
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Individual radiologists
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Subspecialty training in breast imaging
Volume of mammograms read (but see text)
Years since training
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Organization of mammography services
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High volume centers tend to have higher accuracy, above and beyond the increase attributable to reading volume of individual radiologists
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Number of diagnostic exams performed
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Number of image-guided breast interventional procedures (biopsies?) performed
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Double-reading of mammograms by two radiologists improves accuracy51
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Use of computer-assisted detection (CAD) by nonspecialists (but see text)
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Center designated as breast diagnostic and/or screening center or freestanding mammography center
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Availability of prior mammograms for comparison increases specificity
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Health care cystem
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False-positive rates have increased over time in the United States and are higher than in other countries.
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