Mammography in 53,803 women from the New Hampshire Mammography Network

PURPOSE: To describe measures of mammography performance in a geographically defined population and evaluate the interpreter's use of the Breast Imaging Reporting and Data System (BI-RADS). MATERIALS AND METHODS: Mammographic data from 47,651 screening and 6,152 diagnostic examinations from November 1, 1996, to October 31, 1997, were linked to 1,572 pathologic results. Mammographic outcomes were based on BI-RADS assessments and recommendations reported by the interpreting radiologist. The consistency of BI-RADS recommendations was evaluated. RESULTS: Screening mammography had a sensitivity of 72.4% (95% Cl: 66.4%, 78.4%), specificity of 97.3% (95% Cl: 97.25%, 97.4%), and positive predictive value of 10.6% (95% Cl: 9.1%, 12.2%). Diagnostic mammography had higher sensitivity, 78.1% (95% Cl: 71.9%, 84.3%); lower specificity, 89.3% (950/0 Cl: 88.5%, 90.1%); and better positive predictive value, 17.1% (95% Cl: 14.5%, 19.8%). The cancer detection rate with screening mammography was 3.3 per 1.000 women, with a biopsy yield of 22.4%, whereas the interval cancer rate was 1.2 per 1,000. Nearly 80% of screening-detected invasive malignancies were node negative. The recall rate for screening mammography was 8.3%. Ultrasonography was used in 3.5% of screening and 17.5% of diagnostic examinations. BI-RADS recommendations were generally consistent, except for probably benign assessments. CONCLUSION: The sensitivity of screening mammography in this population-based sample is lower than expected, although other performance indicators are commendable. BI-RADS "probably benign" assessments are commonly misused.