Blinded comparison of computer-aided detection with human second reading in screening mammography

The purpose of this study was to compare a human second reader with computer-aided detection (CAD) for the reduction of false-negative cases by a primary radiologist. We retrospectively reviewed our clinical practice.

We found that 6,381 consecutive screening mammograms were interpreted by a primary reader. This radiologist then reinterpreted the studies using CAD ("CAD reader"). A second human reader who was blinded to the CAD results but knowledgeable of the primary reader's findings reviewed the studies, looking for abnormalities not seen by the first reader.

Two cancers were called back by the second human reader that were not called back by the CAD reader; however, the CAD system had marked the findings, but they were dismissed by the primary reader. Because of the small numbers, the difference between the CAD and second human reader was not statistically significant. The CAD and human second readers increased the recall rates 6.4% and 7.2% (p = 0.70), respectively, and the biopsy rates 10% and 14.7%. The positive predictive value was 0% (0/3) for the CAD reader and was 40% (2/5) for the human second reader. The relative increases in the cancer detection rate compared with the primary reader's detection rate were 0% for the CAD reader and 15.4% (2/13) for the human second reader (p = 0.50).

A human second reader or the use of a CAD system can increase the cancer detection rate, but we found no statistical difference between the two because of the small sample size. A possible benefit from a human second reader is that CAD systems can only point to possible abnormalities, whereas a human must determine the significance of the finding. Having two humans review a study may increase detection rates due to interpreter--hence, perceptual--variability and not just increased detection.