Dialog Box

CA125 and ovarian cancer diagnosis

Diagnosing ovarian cancer can be a difficult process. Symptoms are vague, and often mimic other less serious, common conditions including food intolerances, irritable bowel syndrome and symptoms experienced during menstruation and menopause. As a result, many diagnoses are received when the ovarian cancer has spread to other parts of the body, when symptoms are more pronounced. 

How is ovarian cancer diagnosed?

To definitively diagnose and stage ovarian cancer surgery is required to take a tissue biopsy for analysis. However, other methods may be used prior to surgery if your doctor or specialist suspects you may have ovarian cancer.

Physical examination:

A general check up, including an internal pelvic examination.

Imaging tests:

Ovarian cancer is usually identified by Trans Vaginal Ultrasound (TVU) or computed tomography (CT) of the abdomen and pelvis, and the CT scan can see if the cancer has spread throughout the body. It should be noted that this is not a definitive diagnosis, and will still require tissue sample collection. 

Blood tests:

A full blood count may be done, as well as a measure of the blood protein CA125, which is often raised in women with ovarian cancer. Other special ‘tumour markers’ may be tested for, but some tumours will not have elevations of these markers and the type of marker depends on the type of tumour.

What is the CA-125 blood test?

Cancer Antigen 125 is a protein biomarker found in the bloodstream and can be produced by ovarian cancer cells. However, raised CA125 levels can also be caused by menstruation, endometriosis, benign ovarian cysts and other conditions such as liver and kidney disease (Cancer Council). The CA125 blood test analyses the concentration of the biomarker in a patient's blood sample. Results of the CA125 test are measured in units per milliliter (U/mL). The normal value is less than 46 U/mL (Mayo Clinic). 

How can it be used?

The CA125 blood test can be used to help diagnose or exclude ovarian cancer in combination with other tests and scans. Half of all women with early stage ovarian cancer do not have elevated CA125 levels, meaning it cannot be used as a reliable population screening test for ovarian cancer. It can only be used as a tool to assess symptoms suspected to be associated with ovarian cancer. It is more reliable as an indicator for ovarian cancer in postmenopausal women than in pre-menopausal women (Cancer Council Victoria)

A CA-125 blood test can also be used to monitor progression of ovarian cancer, especially during treatment. After assessing baseline CA125 levels in a patient before undergoing treatment, results can be used to determine whether the treatment has been successful or not. A decrease in CA-125 levels during and after treatment can indicate that treatment has been successful, whereas increases may be evidence of a recurrence or further spread of the disease (Healthline).

Should I be having regular CA125 blood tests?

Regular CA125 tests are not recommended for women who are not at an increased risk of ovarian cancer (Cancer Australia), but may be appropriate for those who have a higher risk of ovarian cancer due to genetic factors such as BRCA1 or BRCA2 gene mutations, or Lynch Syndrome associated genes. However, recent studies have noted the limited sensitivity of CA125 in predicting ovarian cancers, with a high number of false positives being recorded and an inability to reliably identify ovarian cancer at an early stage (Cancer Australia).

If you have any concerns about your risk of ovarian cancer, you should discuss these with your GP or trusted health professional.


  1. Early Detection of Ovarian Cancer (Cancer Council)
  2. Ovarian Cancer: Screening (Cancer Australia)
  3. CA125 test (Mayo Clinic)
  4. Diagnosing ovarian cancer (Cancer Council Victoria)
  5. CA125 Blood Test: Purpose, Procedure and Risks (Healthline)
  6. Surveillance of women at high or potentially high risk of ovarian cancer (Cancer Australia)


27 July 2021
Category: Blog
Tags: ca125, diagnosis, explainer,