The sensitivity, specificity, and positive predictive value of screening mammography and symptomatic status

Objective-To examine whether the accuracy of screening mammography varies a ccording to symptomatic status reported at the time of screening. Setting-Victoria, Australia, where free biennial screening is provided to w omen aged 40 and older. Methods-We examined the sensitivity, specificity, and the positive predicti ve value of screening mammography by symptom status in 106 826 women from V ictoria, who attended for first round mammography in 1994 and who did not h ave a personal history of breast cancer. Symptomatic status was divided int o the following categories: asymptomatic; significant symptoms, if the woma n reported a breast lump and/or blood stained or watery nipple discharge; a nd other symptoms, if reported. Unconditional logistic regression modelling was used to adjust for age, use of hormone replacement therapy (HRT), and family history. Results-Sensitivity was lower for women with other symptoms (60.0%) than as ymptomatic women (75.6%), or women with significant symptoms (80.8%). Speci ficity was lower for women with significant symptoms (73.7%) than asymptoma tic women (94.9%), or women with other symptoms (95.4%). Among women who ha d invasive cancer detected during screening interval, women with other symp toms were more likely to get a false negative result (odds ratio 1.79, 95% confidence interval 1.03 to 3.04) than asymptomatic women, after adjusting for age, use of HRT, and family history. Conclusion-The lower sensitivity in women with other symptoms requires furt her investigation. Possible explanations include increased breast density a nd poor image quality. The high sensitivity in women with significant sympt oms is probably due to more cautious radiological practice, which has also resulted in low specificity in this group.