WASHINGTON -- Some radiologists report false positive cancer readings in mammogram X-rays almost 16 percent of the time, with younger and more recently trained doctors making more interpretation errors than their more experienced colleagues, a study found.
The report the Journal of the National Cancer Institute said the rate of false positives could be reduced significantly if radiologists always could compare films from previous mammogram screenings.
Dr. Joann Elmore of the University of Washington School of Medicine in Seattle said the rate of false positives -- breast cancer mammogram screenings that require follow-up tests -- are becoming increasingly common in the United States, but it should not discourage women from having annual screenings.
"Mammography is not a perfect test (for breast cancer), but it is the best test we have," said Elmore, first author of the study. "Women should realize that they have a 10 percent chance of being called back for additional tests."
The results of the study, she said, carry this message: Women should continue to have mammograms, but they should try to return to the same testing facility each time so radiologists can compare past test films. False positives are reduced by about 70 percent when radiologists compare current films with images from past tests, Elmore said.
The study involved an evaluation of mammogram readings from 2,169 women by 24 radiologists in a community clinic practice from the years 1985 to 1993, which gave time for follow-up studies of the patients.
The study analyzed the rate of false-positive interpretations by the doctors, then related that to the experience and training of the radiologists and to the age and other characteristics of the patients.
It found that the false-positive rate ranged from 2.6 percent to 15.9 percent. But when this rate was adjusted for the effect of patient characteristics, such as age, the false-positive rate dropped to 3.5 percent to 7.9 percent.
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