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Mammogram Results May Depend on Doctor

Mammogram Results May Depend on Doctor
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WebMD Health News

Sept. 17, 2002 -- Mammograms are considered the best way to detect early breast cancers, but a new study suggests the test's accuracy is only as good as the doctor who interprets it.

The study's researchers found wide disagreement among community radiologists' interpretation of mammograms. Younger, more recently trained doctors reported false positives or overly interpreted findings two to four times more often than older radiologists. Younger, premenopausal women as well as those on hormone replacement therapy (HRT) were most likely to have false-positive mammogram results.

Studies suggest that as many as one in 10 mammograms are incorrectly considered positive, requiring further testing and possible biopsy. In earlier research, Joann G. Elmore, MD, found that a woman who has annual mammograms over a 10-year period will experience false-positive results 50% of the time

"False positives cause a great deal of anxiety for women, and there is a tremendous economic cost as well," Elmore tells WebMD. "For every $1 million that we spend on screening, we spend another $300,000 to work up false positives."

Elmore and colleagues at the University of Washington School of Medicine, Harborview Medical Center, examined results from 24 radiologists' interpretations of 8,700 mammogram screenings over an eight-and-a-half year period. Their findings are reported in the Sept. 18 issue of the Journal of the National Cancer Institute.

The community radiologists varied widely in their diagnostic interpretations and in recommendations for additional screenings and biopsies. False-positive readings ranged from a low of 2.6% to a high of 15.9%. However, after patient and radiologist characteristics were taken into account, the degree of difference in interpretation narrowed to 3.5%-7.9%. Patient characteristics were important factors in incorrect readings, with more false positives reported for women who were younger, premenopausal, on HRT, or had a family history of breast cancer.

Younger doctors who had most recently finished medical school were far more likely to falsely interpret mammograms as having an abnormality. But the study design made it impossible to determine if these doctors were also finding more cancers than those who had lower false-positive rates.

"We don't know if these younger doctors are being trained to emphasize sensitivity over specificity, or if they are not as accurate because they have less experience," Elmore says. "Reading mammograms is a skill, and studies show that those who read more of them over a longer period tend to do a better job."

In an editorial accompanying the study, medical statistician Larry G. Kessler and colleagues from Seattle's Fred Hutchinson Cancer Research Center conclude that requiring two or more radiologists to interpret a single mammogram would reduce misleading results. They noted that about half of the countries where routine mammogram screenings are performed have a double reading policy.

But a shortage of radiologists in the United States makes it unlikely that practice will be widely adopted here anytime soon, Kessler tells WebMD.

"Multiple readings is the standard of care in some practices and many academic centers in this country," he says. "A woman who is concerned can find out a radiologist's false-positive rate, and she should ask if they routinely do double readings. Someone whose sole concern is making sure that a cancer is caught may accept a higher false-positive rate. Others may find a high rate unacceptable."

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