Independent double reading of screening mammograms in The Netherlands: effect of arbitration following reader disagreements.

PURPOSE: To prospectively determine the value of arbitration by a panel of radiologists when two radiologists performing independent readings of screening mammograms do not reach a consensus about referral.
MATERIALS AND METHODS: The study population consisted of women who participated in the Dutch Nationwide Breast Cancer Screening Program, in which biennial screening is offered to women aged 50-75 years. An arbitration panel of three radiologists assessed those screening mammograms for which two screening radiologists did not reach a consensus about referral necessity. Women were referred for further analysis if at least one arbitration panel radiologist considered referral to be necessary.
RESULTS: The two screening radiologists agreed on the recommendation for referral of 498 (0.8%) of 65,779 screened women and on the recommendation for no referral of 64,949 (98.7%) women. They initially disagreed about the referral in 332 (0.5%) cases. After a mutual consultation, disagreement persisted regarding 183 (0.3%) mammograms. The arbitration panel referred 89 of these cases for further analysis, which revealed cancer in 20 (22%) cases. In three (3%) of the 94 cases that were not referred by the panel, breast cancer was detected at the site of previously discrepant mammographic findings seen at subsequent screening performed 2 years later. If all 183 discrepant cases had been referred, the referral rate would have increased from 0.8% to 0.9% at subsequent (incident) screenings and from 1.5% to 1.7% at initial screenings. In addition, at subsequent screenings, the number of cancers detected per 1,000 women screened would have increased from 4.4 to 4.5.
CONCLUSION: Mammograms with discrepant findings constitute a very important subset of screening mammograms. All lesions that are subsequently proved to be malignant may not be detected with panel arbitration.