Ovarian Cancer Screening Blood Test

CA-125 screening tool has its benefits and limitations

Nurse taking blood from patient, close up
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A CA-125 test is a screening tool used to measure the amount of a protein (CA-125) in the blood. Elevated levels can be an indication of ovarian cancer in some women or suggest that cancer is returning in others previously been treated for the disease.

The test can also be used to monitor the effectiveness of ovarian cancer therapy by tracking whether the CA-125 level is dropping, a good indication that treatment is working.

Value of the CA-125 Test

An antigen is any substance that causes your body to produce an immune defense against it. CA-125 (cancer antigen-125) is a type of protein found on the surface of ovarian cancer cells that can trigger this defense.

A simple test (sometimes referred to as a CA-125 tumor marker) is used to measure CA-125 in the blood. It also can evaluate other body fluids such as those from the chest or gastrointestinal tract.

The CA-125 test is one of two such assays that doctors use to investigate ovarian cancer. The other is the transvaginal ultrasound (TVUS), an imaging technology which uses sound waves to identify masses and other abnormalities the female reproductive tract. Together, the tests can help doctors pinpoint a developing tumor on the ovaries.

What neither can do is determine whether any mass or tumor is benign (cancerous) or malignant (noncancerous).

Limitations of the CA-125 Test

While the CA-125 test is a valuable tool, it is not recommended as a general screening test due to its high rate of false-positive results.

Elevated CA-125 levels can be caused not only by ovarian cancer but a myriad of others conditions. This can lead to misdiagnoses and unnecessary surgical procedures.

Among the conditions associated with high CA-125 readings:

  • uterine fibroids
  • first-trimester pregnancy
  • menstruation
  • pelvic inflammatory disease (inflammation of the ovaries, fallopian tubes, or uterus)
  • endometriosis (a condition where tissue inside the uterus suddenly grows outside of it)
  • diverticulitis (the inflammation of pouches inside the bowel wall)
  • pancreatitis (inflammation of the pancreas)
  • cirrhosis (scarring of the liver)
  • lupus (an autoimmune disorder)
  • recent abdominal surgery
  • other types of cancer
  • certain chemotherapy drugs used in cancer treatment
  • a radioactive scan

At the same time, not all women who have ovarian cancer have elevated CA-125 levels. These types of variations can cause "blind spots" when diagnosing the disease.

Several recent studies have shown that co-testing with CA-125 and TVUS in women of average risk often led to more surgery but no reduction in the rate of ovarian cancer deaths.

Who Should Get the CA-125 Test

The CA-125 test does have its benefit for women at high risk of ovarian cancer. If you have a strong family history of ovarian or breast cancer, you doctor may recommend routine CA-125 screenings as a preventive measure. This will often be the case if a doctor discovers that you have a BRCA1 or BRCA1 mutation. Both of these genetic mutations are associated with the high risk of breast and ovarian cancer.

Some women who have been successfully treated for ovarian cancer may opt to have regular CA-125 screenings.

This is still under debate by researchers, many of whom question the value of the test in identifying cancer recurrence.

A Word From Verywell

While scientists continue to search for new ways to diagnose ovarian cancer early, there are common signs and symptoms associated with the disease that women should be aware of, including:

  • bloating
  • pelvic or abdominal pain
  • trouble eating or feeling full quickly
  • urinary urgency (feeling like you have to pee all the time)

If any of these symptoms persist for more 12 months, go see your gynecologist. In the end, you may be your best, first-line defense against ovarian cancer.