Sensitivity and specificity of first screen mammography in 15 NBSS centres

We report the sensitivity and specificity of first screen mammography in a 15-centre randomized screening trial. Of 44,718 women who received mammography and physical examination at first screening, 238 were diagnosed with breast cancer at first screen, 34 in the 12-month interval after the first screen, and 98 at the second screen. Seventeen of the interval cases and 47 of the second-year cancers were defined as potentially detectable at first screening. Interpretations of first screen mammograms by radiologists at the screening centres were matched to known histological outcomes. Simultaneous blind review of 2908 cases, which included all cancers detected at first and second screenings as well as interval cancers, was done by a single reference radiologist. The sensitivity of the technique as carried out at all NBSS centres was 0.75, the specificity 0.94, the positive predictive value 0.07, and the negative predictive value 0.998.