Purpose: To evaluate the impact of the number of readers on sensitivity and specificity, and compare it with conference consensus reading.
Material and methods: Eight readers read mammography films of 200 women (including 35 false-negative and 16 screen-detected cancers). The sensitivities and specificities of the two methods were calculated: either at least a single cancer-positive opinion within the group (summarized independent reading) or the cancer-positive opinion of the reader majority (conference consensus reading) was considered decisive.
Results: The mean sensitivity for summarized independent readings of different groups was 64.7% as compared to the 43.1% mean sensitivity of conference consensus readings. The mean specificities were 92.4% and 97.7%, respectively. The greatest sensitivity of 74.5% was achieved when the readings of the four best-performing readers were combined.
Conclusion: The sensitivity of reading is maximal when any positive opinion within a pair or a group of readers is taken into consideration. Discordant double reading may best be judged as screening positive, and the value of a third opinion should be questioned.