Doctors use several diagnostic tests, including blood tests, in order to look for signs of ovarian cancer. In some cases, certain test results may not detect anything unusual even when the doctor determines that a person has ovarian cancer.

Although blood tests can provide clues as to whether cancer cells might be present, they alone can’t confirm whether or not a person has ovarian cancer. A biopsy is needed in order to know for sure.

During a biopsy, doctors remove a small sample of tissue — usually during surgery — and study it in the laboratory to see if it contains cancer cells. It’s possible to find ovarian cancer during a biopsy in spite of having normal blood test results.

Blood Tests Used During Ovarian Cancer Diagnosis

During the process of diagnosing possible ovarian cancer, your health care team may use a variety of tests. One of the main blood tests that can shed light on possible ovarian cancer is the CA-125 blood test. If ovarian cancer is found, your doctor may also use additional tests to determine the type of ovarian cancer.

Your doctor may also run other blood tests to look at different measures of your overall health. These may include tests to evaluate how well your kidneys or liver are working, or a complete blood count, which measures levels of different types of blood cells.

The CA-125 Blood Test

Cancer antigen 125 (CA-125) is a protein often made by ovarian cancer cells. The cells release CA-125 into the bloodstream, which allows the protein to be measured with a blood test.

Most people — healthy males and females included — have low levels of CA-125 in their blood. Having less than 35 units per milliliter falls within what is considered the normal range. Various health conditions, including cancer, can cause CA-125 levels to rise beyond this level.

Doctors may use a CA-125 blood test to:

• Screen people with a higher risk of ovarian cancer (like those with BRCA1 or BRCA2 gene mutations)
• Gauge whether ovarian tumors are responding to cancer treatment
• Determine if ovarian cancer has returned after treatment

What Could High CA-125 Levels Mean?

When CA-125 levels are higher than normal, it could mean that a person has ovarian cancer. The majority of people with ovarian cancer have increased levels of this protein.

A high level of CA-125 can also be a sign of other non-cancerous conditions, such as:

• Infections in the uterus, ovaries, or fallopian tubes (pelvic inflammatory disease)
• Endometriosis
• Uterine fibroids
• Diverticulitis
• Pneumonia
• Liver disease
• Pregnancy
• Congestive heart failure
• Menstruation

Having high CA-125 levels doesn’t automatically indicate cancer. If you show high levels on a blood test, your doctor will perform further testing, such as a biopsy. This clarifies whether cancer or a different condition caused the test results.

What Could Normal CA-125 Levels Mean?

For some people, normal results on a CA-125 test may mean no ovarian cancer exists within their body. However, normal results are not a guarantee of this. That’s because not all ovarian tumors make CA-125. High levels of the protein are found in about 80 percent of ovarian cancer cases. This means that 1 in 5 people can have normal CA-125 levels but still have ovarian cancer.

Results also vary depending on a person’s ovarian cancer stage. Early-stage tumors are less likely to produce CA-125 than are advanced-stage tumors.

In fact:

• About 50 percent to 60 percent of participants with stage 1 ovarian cancer have high CA-125 levels.
• About 75 percent to 90 percent of people with stage 2, 3, or 4 ovarian cancer have elevated CA-125.

Blood Tests To Determine the Type of Ovarian Cancer

There are three main types of ovarian tumors: epithelial, germ cell, and stromal. If your doctor suspects that you have a certain ovarian cancer type, they may run additional blood tests. These tests look for tumor markers — molecules made by or found inside cancer cells. Finding high levels of a particular tumor marker may mean that a certain type of cancer cell is present within the body.

Epithelial Ovarian Cancer

Epithelial ovarian tumors — the most common type of ovarian cancer — grow from the cells that cover the surface of the ovaries. Cancers of the fallopian tubes (tubes that carry egg cells from the ovary to the uterus) and/or peritoneum (inner lining of the abdomen) are usually grouped with epithelial ovarian tumors. That’s both because those cancers grow similarly to ovarian cancer, and because doctors treat them in a similar manner.

Human epididymis protein 4 (HE4) is a tumor marker made by epithelial ovarian cancer cells. Researchers are studying whether HE4 levels can be used to identify cases of epithelial ovarian cancer or to help predict outlook in people with other types of cancer.

Germ Cell Tumors

Germ cell tumors are formed from the same cells in the ovaries that make eggs. Germ cell tumors of the ovary most often develop in teens or young adults. Sometimes, germ cell tumors lead to high levels of certain tumor markers. Doctors sometimes use blood tests to look for one or more of these markers.

The noteworthy markers include:

• Human chorionic gonadotropin — A hormone normally produced during pregnancy
• Alpha-fetoprotein — A protein usually only made by a fetus during development
• Lactate dehydrogenase — An enzyme that may be released at high levels by cancer cells or by cells that have become damaged

Stromal Tumors

Stromal tumors grow out of cells that make up connective tissue, which helps give the ovaries their shape and hold the rest of the cells together. The connective tissue also makes some of the female sex hormones.

Stromal tumors can, in some cases, lead to higher levels of inhibin, a protein that helps control ovulation (release of an egg from the ovary). Because ovarian stromal tumors affect the hormone-producing cells, they may also elevate levels of the hormones estrogen and testosterone.

What if Tumor Marker Tests Are Negative?

Ovarian tumors don’t always produce the same tumor markers. Not all cases of ovarian cancer will lead to high levels of the markers mentioned above. Additionally, there are many ovarian tumor subtypes within each of the three main categories that may lead to varying tumor marker levels.

Blood tests may not be able to determine the tumor type. However, a biopsy can determine for sure whether cancer cells are present and what type of ovarian tumor they make up.

Talk With Others Who Understand

On MyOvarianCancerTeam, the social network for people with ovarian cancer and their loved ones, nearly 4,000 members come together to ask questions, give advice, and share their stories with others who understand life with the disease.

Have your blood tests been normal despite a diagnosis of ovarian cancer? Share your experiences in the comments below, or start a conversation by posting on your Activities page.