An assessment of the influence of clinical breast examination reports on the interpretation of mammograms in a breast screening program.
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The population-based Ontario Breast Screening Program (OBSP) provides two-yearly screening by both nurse examiner clinical breast examination (CBE) and two-view mammography to women aged 50 to 69. CBE alone accounts for about 5% of cancer detection. The purpose of this study was to determine whether CBE information affects radiologists' interpretation of mammography. Interpretation was defined by 1) radiologists' referral rates for diagnostic evaluation and 2) radiologists' accuracy in distinguishing cancer from non-cancer on mammograms. Mammograms were obtained from women randomly selected from those screened in the OBSP between 1990 and 1992. Selection was stratified by whether or not the nurse examiner had independently referred for diagnostic evaluation. Additional women diagnosed with breast cancer were selected to increase the precision of the receiver-operating characteristic (ROC) curve. Each participating OBSP radiologist read a set of mammograms twice, approximately three weeks apart. The first reading was based on mammograms alone. At the second reading, the CBE report was included on the reporting form. Among 620 women referred by the nurse, radiologist referral rate increased from 37.7% to 40.8% (p = 0.079) when CBE information was available. Among the 637 not referred by the nurse, radiologist referral rate decreased from 29.8% to 25.6% (p = 0.005). There was little effect on the sensitivity and specificity of radiologist referral and the areas under the two ROC curves (with and without CBE information) were not significantly different (p = 0.571). Although there was some effect of CBE information on radiologists' pattern of referral, there was no effect on accuracy of cancer detection.
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