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Despite what its name might imply, the ovarian cancer blood test CA-125 is NOT a screening test for ovarian cancer. Doctors use this blood test to monitor response to ovarian cancer therapy, and to pick up possible recurrence of cancer during treatment.

If you have a family history of reproductive cancer, your doctor may recommend this test for you — as one tool in their diagnostic tool kit — but again, it’s not used as an early screening test for ovarian cancer. Unless you have a known genetic mutation that predisposes you to ovarian cancer, it’s unlikely your doctor would recommend this test.

In this article, we take a look at how this blood test works, who it’s recommended for, and how doctors interpret the results.

An antigen is a substance in your body that can provoke an immune response. A cancer antigen is a protein that’s found on cancer cells.

Cancer antigen 125 (also called CA-125) is the cancer antigen linked to ovarian cancer. The CA-125 blood test is the test that measures its presence in your body.

Doctors use the CA-125 blood test to detect whether current treatments are decreasing the number of ovarian cancer cells in your body.

Why the CA-125 blood test is not used as a screening test for ovarian cancer

A number of other health conditions can elevate your levels of the CA-125 antigen, which is one reason why the blood test is NOT used as a screening test for ovarian cancer.

CA-125-elevating conditions include:

The Ovarian Cancer Research Alliance (OCRA) says that this test isn’t useful for ovarian cancer screening because in 20 percent of advanced ovarian cancer cases and 50 percent of early ovarian cancer cases, the CA-125 antigen is not elevated. That means this test can suggest that cancer is present when it isn’t, and it can miss present cancer.

For this reason, the OCRA says that the National Cancer Institute does not currently recommend the CA-125 blood test as a screening method for detecting ovarian cancer.

While the CA-125 blood tests does have serious limitations, there are people for whom the test results might provide important information. For example, you might be a good candidate for the CA-125 blood test if you have:

  • been undergoing treatment for ovarian cancer and need to see how effective the treatment has been
  • completed therapy for ovarian cancer and are being monitored for recurrence

If you have concerns about your risk of ovarian cancer, don’t hesitate to discuss them with a primary care physician or an OB-GYN. Your health professionals should be aware of any health history of cancer or any risk factors that run in your family.

Ovarian cancer symptoms to look out for include:

  • pelvic pain
  • abdominal swelling
  • changes in your appetite
  • unexplained weight loss
  • increased urination
  • constipation or diarrhea
  • changes in your period

Reach out to a doctor if you have any concerns

The early symptoms of ovarian cancer can be easy to overlook. That’s why it’s important to be aware of these symptoms, and don’t wait to reach out to a doctor if you notice any of them occurring.

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The CA-125 blood test is not recommended as a screening test for ovarian cancer. However, it can give doctors valuable information about whether treatment for ovarian cancer is working, and whether cancer has returned following treatment.