The CA125 blood test is designed to measure the amount of a specific protein that is in the blood. Called “Cancer Antigen 125,” it is primarily used as a tumor marker for women who are suspected to have ovarian cancer. It will also be ordered to detect whether the cancer has returned after a treatment plan has been completed. A series of CA125 tests is usually considered to be more useful than one specific test result.

It is not uncommon for the CA125 blood test to be ordered with an ultrasound to monitor women who are believed to be at a high risk for ovarian cancer, but do not have the disease as of yet. Certain risk factors place women into this category, including a family history of ovarian cancer, increasing age, infertility issues, obesity, and hormone replacement therapy use.

The most significant risk factor, however, is an inherited genetic mutation on the BRCA1 or BRCA2 genes, which are breast cancer genes.

When is the CA125 Blood Test Ordered?

The CA125 blood test may be ordered before treatment begins for ovarian cancer to create a baseline result that can measure future outcomes. Interval testing may also be ordered by medical providers when they consider a woman to fit into the high risk category. Certain physical exam findings, such as a pelvic mass, may also trigger this blood test to be ordered.

Some women may ask about having the CA125 blood test ordered as a preventative measure. For women who do not fit into the high risk category, the results of this test are considered to be non-specific. This means the blood test alone cannot determine if ovarian cancer is present.

What Do the CA125 Blood Test Results Mean?

The CA125 blood test will either be positive or negative. Having a positive test does not necessarily mean that cancer is present. A negative test may also not mean that there isn’t cancer present. This is why the test is considered to be non-specific and not suitable for screening purposes.

Several benign conditions have been known to create positive test results. This includes a heavy menstruation cycle, pelvic inflammatory disease, endometriosis, or even pregnancy.

For some tumors, a second test called the HE4 blood test may be ordered to monitor epithelial cells. These cells are found in the most common type of ovarian cancers, developing from cells that are found outside of the ovaries.

Should You Insist on the CA125 Blood Test?

Some women receive emails about the CA125 blood test and receive well-intentioned social media posts and updates regarding what this test can do. The suggestion is that all women should demand that this blood test be completed each year for ovarian cancer. If you fit into a very high risk category, then women are encouraged to insist on yearly testing, along with other test options, to monitor their health so that the cancer can be detected quickly.

For women without a family history of ovarian cancer or a lack of other risk factors, then CA125 screening will be ineffective. The test may be low cost and potentially covered by a health insurance policy in the US, but produce results that are essentially useless on their own.

Even in women who are in the high risk category, it is unclear whether using the CA125 blood test can actually lower the chances of dying from ovarian cancer or being able to detect it at an early stage.

About 1 in 5 women have ovarian cancer found at an early stage. In this group, there is a 94% patient survival rate at 5+ years post-diagnosis. The best way to find this disease in its earliest stages is to have regular health exams scheduled. See a medical provider if you have symptoms, such as abdominal swelling, pressure, and pain. If there is no improvement in these symptoms or they worsen, then schedule an appointment immediately.

Researchers are continuing to look for and develop new tests that can help find ovarian cancer in its earliest stages for women. At the moment, there are no accurate screening tests, but the CA125 blood test is a viable option for some and to monitor for treatment response. Ask your medical provider if this test would be useful for you and ask questions about your health based on this guide to make sure you can limit your risks as much as possible.