Acta Medica Academica (Nov 2011)
Th e infl uence of breast density on the sensitivity and specifi city of ultrasound and mammography in breast cancer diagnosis
Abstract
Objective. Th e aim of this study was to analyse the sensitivity and specificity of ultrasound and mammography according to breast densityand determine which of these diagnostic imagings is a more accuratetest for diagnosis of breast cancer. Patients and methods. By meansof a cross-sectional study, ultrasound and mammographic examinationsof 148 women with breast disease symptoms were analysed.All women underwent surgery and all lesions were examined by histological examination which revealed the presence of 63 breast cancers,and 85 benign lesions. Histological examination was used as the “goldstandard”. In relation to breast density, the women were separated into two groups, group A: women with “fatty breast” (ACR BI-RADS density categories 1 and 2) and group B: women with “dense breast”(categories 3 and 4). Ultrasound and mammographic findings were classified on the BI-RADS categorical scale of 1-5. For statistical data processing, the logistic regression analysis and the McNemar chi-square test for paired proportions was used. Th e differences on the level of p<0.05 were considered statistically significant. Results. In the group of women with breast density categories 1 and 2 the difference in the sensitivities (p=1) as well as in the specificities (p=0.11) of the two imaging tests was not statistically significant. In the group of women with breast density categories 3 and 4 the ultrasound sensitivity was significantly higher than the mammographic sensitivity (p=0.03) without a statistically significant difference in specificity (p=0.26). Sensitivity of mammography was (linearly – ex; linearity exists between breast density and the logarithm of odds for a positive result) associated with breast density (likelihood ratio χ2 =15.99, p =0.0001). Th e odds ratio for (the probability of – ex) a positive mammographic result was 0.25 (95% CI, 0.11-0.58). Thesensitivity of ultrasound and specificity of each test were not (linearly - ex) associated with breast density. Conclusion. Breast density had a significant influence on the sensitivity of mammography but not on specificity. Th is is very important because a certain percentage of women, not only under 40 but also aft er 40, have heterogenous and extremely dense breasts (density categories 3 and 4). In these women, ultrasound is a more accurate imaging test than mammography, while in the women with fatty breasts (density categories 1 and 2) these imaging tests are almost equally accurate in breast cancer diagnosis.
