Mammograms are used as a screening test for detecting breast cancer in women of all ages. The main goal of any cancer-screening test is to correctly identify people who have cancer. This is also called the sensitivity of the test.
A test that has the sensitivity of 90 percent means that 90 percent of people tested who truly have cancer are correctly identified as having cancer, and 10 percent are missed or misdiagnosed.
The sensitivity of a mammogram, according to Susan G. Komen, is 84 percent. What that means is a mammography correctly identifies about 84 percent of women who truly have breast cancer. Sensitivity is known to be higher among older women. A high sensitivity means few cases are missed when using the test.
The accuracy of a mammogram can depend on a variety of factors such as:
It is more difficult to interpret results for younger women due to the fact that breasts of younger women contain more glands and ligaments than those of older women. More glands means higher breast density which can obscure signs of cancer.
The reason sensitivity of a mammogram is higher among older women is because with age, breast tissue becomes fattier and has fewer glands, which makes it easier to interpret mammogram results.
2) Menopausal Hormone Therapy
Another factor that can affect accuracy of mammograms is menopausal hormone therapy. MHT increases the risk of breast cancer and increases the difficulty of reading mammograms because it causes an increase in breast density.
Results from the Women’s Health Initiative, a study cited on a Susan G. Komen web article on accuracy of mammograms, found that women who take MHT had breast cancer that was at a more advanced stage than women who did not take MHT.
This was found to be true in women taking estrogen as well as progesterone. Women who took either type of MHT (estrogen and progesterone, or estrogen alone) are found to have higher breast density, which can cause a need for additional follow-up testing.
3) The Type of Mammography Test Used