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.