Up to 10 percent of all mammograms are false positives, that is, they suggest abnormalities that upon further testing end up to be harmless. These false positives create anxiety for women and lead to costly further testing—such as additional mammography or ultrasound—to rule out breast cancer. When radiologists always have access to women's previous mammograms, the incidence of false-positive mammogram readings is reduced by at least half, concludes a study supported by the Agency for Healthcare Research and Quality (HS10068).
Andrew N. Kleit, Ph.D., of the Pennsylvania State University, and James F. Ruiz, M.D., of the Women's Hospital of Baton Rouge, analyzed 1999 medical data on screening and diagnostic mammograms for 5,000 patients at a single Southern hospital. They compared the results of followup exams of women whose initial mammograms were positive (suggesting a problem). They also examined the influence of factors such as whether the woman had received a prior mammogram, her age, and individual physician identifiers on false-positive readings.
Results implied that if previous mammograms were always available, the number of false positives would decrease by at least half. The findings also indicated that there was no reason to believe this decrease would be accompanied by an increase in the number of false negatives (mammograms said to be normal that were not). Other factors also affected the number of false positives. Mondays and Wednesdays appeared to be more prone to false positives than other days of the week. There was also some disparity in false-positive outcomes among the five physicians studied.
See "False positive mammograms and detection controlled estimation," by Drs. Kleit and Ruiz, in the August 2003 Health Services Research 38(4), pp. 1207-1228.
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