The role of arbitration of discordant reports at double reading of screening mammograms.

OBJECTIVE: To asses the effectiveness of arbitration of discordant double readings in mammography screening.
DESIGN: A retrospective study of 1217 consecutive arbitrations.
SETTING: A subset of discordant double readings from the Florence screening programme underwent arbitration by a third reader.
RESULTS: Positive arbitration of 1217 discordant double readings prompted assessment in 476 cases (39.2%), detecting 30 cancers (6.3%). Of 741 negative arbitrations (60.8%), 311 have been followed up thus far, and two cancers (0.64%) occurred in the site previously suspected at one of the two independent readings. Arbitration had a sensitivity of 86.3% and a negative predictive value of 99.3%. Arbitration reduced the overall referral rates from 3.82% to 2.59% (relative decrease 32.1%). Due to false-negative arbitration, cancers detected per 1000 women screened would decrease from 4.58 to 4.50 (relative decrease 1.7%). For every cancer missed due to false-negative arbitration, 151 unnecessary recalls and 21,248 euro would have been saved, whereas the saved cost per screened woman due to arbitration was 1.72 euro. DISCUSSION: Arbitration of discordant double reading would substantially reduce referral rates with a limited reduction in cancer detection rate, and may be recommended as a routine procedure. Greater benefit from arbitration might be expected in the presence of high referral rates at independent double reading, a common scenario in a newly implemented service screening.