Mammographic breast density and age are important predictors of the accuracy of screening mammography. Although HRT use is not an independent predictor of accuracy, it probably affects accuracy by increasing breast density.

African-American women are less likely to receive adequate mammographic screening than white women, which may explain the higher prevalence of advanced breast tumors among African-American women. Tumor characteristics may also contribute to differences in cancer outcomes because African-American women have higher-grade tumors than white women regardless of screening. These results suggest that adherence to recommended mammography screening intervals may reduce breast cancer mortality rates.