TABLE 3-3 Factors That Affect the Quality of Screening Mammography

Primary Source of Variation

Underlying Sources of Variation

Case Variation

Breast density

Breasts that are mammographically dense are associated with more false positives and false negatives42,65

  • Hormone replacement therapy generally increases breast density.

  • Menopause generally lowers breast density.

  • Overweight women usually have less dense breasts.

  • Breast density usually decreases with age.

Breast cancer history

Family history of breast cancer63

Previous biopsy

Practice Variation

Individual radiologists

Subspecialty training in breast imaging

Volume of mammograms read (but see text)

Years since training

Organization of mammography services

  • High volume centers tend to have higher accuracy, above and beyond the increase attributable to reading volume of individual radiologists

  • Number of diagnostic exams performed

  • Number of image-guided breast interventional procedures (biopsies?) performed


Double-reading of mammograms by two radiologists improves accuracy51


Use of computer-assisted detection (CAD) by nonspecialists (but see text)


Center designated as breast diagnostic and/or screening center or freestanding mammography center


Availability of prior mammograms for comparison increases specificity

Health care cystem

False-positive rates have increased over time in the United States and are higher than in other countries.

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