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% CI: 66.4%, 78.4%), specificity of 97.3% (95% CI: 97.25%, 97.4%), and positive predictive value of 10.6% (95% CI: 9.1%, 12.2%). Diagnostic mammography had higher sensitivity, 78.1% (95% CI: 71.9%, 84.3%); lower specificity, 89.3% (95% CI: 88.5%, 90.1%); and better positive predictive value, 17.1% (95% CI: 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.