Comparing a mammogram with previously obtained images greatly enhances the accuracy of evaluation. NEW YORK (Reuters Health) - Comparing a mammogram with previously obtained images greatly enhances the accuracy of evaluation, Dutch researchers report in the January issue of Radiology.

"In mammography screening," lead investigator Dr. Antonius A. J. Roelofs told Reuters Health, "viewing current mammograms in association with prior mammograms significantly affects performance positively...and may decrease the number of false alarms by as much as 44%."

Dr. Roelofs of Radboud University Nijmegen Medical Center and colleagues note that although such comparisons are made routinely with film-based screening, the transition to digital mammography presents a number of financial, administrative and technical problems in continuing the practice.

To investigate how important prior mammograms might be, 12 experienced screening radiologists used digital displays to read 160 soft-copy screening mammograms twice -- once with and once without prior mammograms.

Eighty of the mammograms were obtained from women who were later diagnosed with breast cancer, while the other 80 mammograms were from women with normal or benign results.

"When only positive cases were considered, no difference was observed," Dr. Roelofs' group reports. However, when prior screening mammograms were available, reading performance was significantly improved.

Moreover, Dr. Roelofs added that a compromise approach "limiting the availability of prior mammograms to cases selected by the reading radiologists, appeared to reduce the large beneficial effect of prior mammograms significantly."

This research, he continued, "proves the importance of prior mammograms in the reading process, and quantifies the effect on the radiologists' reading performance."

"Besides that," Dr. Roelofs concluded, "it shows that radiologists cannot reliably predict for which current mammograms the prior mammograms are necessary in the assessment of certain areas in the mammogram."

Radiology 2007;242:70-77.