Effect on sensitivity and specificity of mammography screening with or without comparison of old mammograms

Purpose: To evaluate the effect of old mammograms on the specificity and sensitivity of radiologists in mammography screening. Material and Methods: One hundred and fifty sets of screening mammograms were examined by 3 experienced screeners twice: once without and once in comparison with older mammograms. The films came from a population-based screening done during the first half of 1994 and comprised all 35 cancers detected during screening in 1994, 12/24 interval cancers, 14/34 cancers detected in the following screening and 89 normal mammograms. Results: Without old mammograms, the screeners detected an average of 40.3 cancers (range 37-42), with a specificity of 87% (85-88%). With old mammograms, the screeners detected 37.7 cancers (range 34-42) with a specificity of 96% (94-99%). The change in detection rate was not significant. However, the increase in specificity was significant for each screener (p=0.0002-0.03). Conclusion: Mammography screening with old mammograms available for comparison decreased the false-positive recall rate. The effect on sensitivity, however, was unclear.