Is Confidence of Mammographic Assessment a Good Predictor of Accuracy?

OBJECTIVE: Interpretive accuracy varies among radiologists, especially in mammography. This study examines the relationship between radiologists' confidence in their assessments and their accuracy in interpreting mammograms. MATERIALS AND METHODS: In this study, 119 community radiologists interpreted 109 expert-defined screening mammography examinations in test sets and rated their confidence in their assessment for each case. They also provided a global assessment of their ability to interpret mammograms. Positive predictive value (PPV) and negative predictive value (NPV) were modeled as functions of self-rated confidence on each examination using log-linear regression estimated with generalized estimating equations. Reference measures were cancer status and expert-defined need for recall. Effect modification by weekly mammography volume was examined. RESULTS: Radiologists who self-reported higher global interpretive ability tended to interpret more mammograms per week (p = 0.08), were more likely to specialize (p = 0.02) and to have completed a fellowship in breast or women's imaging (p = 0.05), and had a higher PPV for cancer detection (p = 0.01). Examinations for which low-volume radiologists were "very confident" had a PPV of 2.93 times (95% CI, 2.01-4.27) higher than examinations they rated with neutral confidence. Trends of increasing NPVs with increasing confidence were significant for low-volume radiologists relative to noncancers (p = 0.01) and expert nonrecalls (p < 0.001). A trend of significantly increasing NPVs existed for high-volume radiologists relative to expert nonrecall (p = 0.02) but not relative to noncancer status (p = 0.32). CONCLUSION: Confidence in mammography assessments was associated with better accuracy, especially for low-volume readers. Asking for a second opinion when confidence in an assessment is low may increase accuracy.