Screening mammography in community practice: positive predictive value of abnormal findings and yield of follow-up diagnostic procedures.

OBJECTIVE: The purpose of this study was to gather from 50 community mammography practices that were included in the National Survey of Mammography Facilities data concerning abnormal findings on screening mammograms to determine the frequency of various recommendations made for patients who had abnormal findings and to compare these recommendations with the frequency with which the procedures were actually performed. We also determined the positive predictive value of screening mammograms (the number of cancers detected per 100 abnormal findings) and the yield (the number of cancers detected per 100 procedures done) of various diagnostic procedures done because of abnormal findings. MATERIALS AND METHODS: We identified 1717 screening mammograms done in the last half of 1991 that had abnormal findings. Radiologic recommendations and follow-up procedures, including repeat standard (screening) mammography, additional mammographic views, sonography, clinical breast examination, needle aspiration, needle biopsy, and open biopsy, were identified for all of the cases from the radiologic records, and follow-up data were obtained from referring physicians. The positive predictive value and yield in the National Survey of Mammography Facilities were compared with data from the mammography screening practice of the University of California at San Francisco (UCSF), a facility noted for its clinical efficiency. RESULTS: We estimate that 11% of all screening mammograms resulted in a recommendation for further diagnostic procedures. These 1717 mammograms with abnormal findings led to the following recommendations and procedures: repeat standard (screening) mammography, 610 (recommended)/635 (performed); additional mammographic views, 785/707; sonography, 400/345; biopsy, 189/229; and needle aspiration, 21/51. More procedures were done than were recommended in some cases because the results of certain procedures often led to the performance of other, additional procedures. The positive predictive value for screening examinations with abnormal findings was 3.5%, and the yield for open biopsy was 21%. In the UCSF data base, the positive predictive value for examinations with abnormal findings was 10%, and the yield for open biopsy was 34%. CONCLUSION: The positive predictive value for examinations with abnormal findings and the yield for diagnostic procedures performed as a result of abnormal findings in 50 community radiologic facilities were higher than those reported in some earlier studies, a fact that raised concern about the induced cost of screening mammography. However, these values were low compared with those in the UCSF data base. This fact was particularly true of repeat standard (screening) mammography.