Which Laboratory Tests Are Used to Diagnose Cancer?

Laboratory technician

When cancer is suspected, your doctor will do a complete evaluation that will include a variety of tests. A complete evaluation includes your health history, a physical exam, and diagnostic testing. When conducting laboratory tests for cancer, samples of blood, urine, and other bodily substances are examined for abnormal cells or tumor markers, both of which may indicate the presence of cancer. 

Diagnostic testing may be used to either confirm or rule out the presence of disease. It also may be used to monitor disease, assess treatment plans, and see how well treatment is working. Certain lab tests may be used to check and monitor whether a patient has a cancer recurrence, or if a new type of cancer has developed. 

Here are the most common lab tests used to diagnose cancer:

Blood tests:

CBC (Complete Blood Count):

A Complete Blood Count (CBC) measures the number of blood cells in the bloodstream. A CBC may be used to diagnose certain types of cancers, such as leukemia and lymphoma. 

A CBC measures the amount of 3 types of cells in your blood:

Red blood cells: Red blood cells carry oxygen throughout your blood. A red blood cell count measures the number of red blood cells in a sample of blood. The two most common ways to measure your red blood cells are through the hemoglobin and the hematocrit part of the CBC. 

White blood cells: A white blood cell count measures the total number of white blood cells in a sample of blood. White blood cells protect your body from infection by attacking invading bacteria and viruses.

Platelets: A platelet count measures the number of platelets in a sample of blood. Platelets help with blood clotting.

A CBC may be used to diagnose a variety of conditions, but it’s commonly used in part with other laboratory tests to diagnose cancer. A CBC can also be used to get an idea of your overall health and find problems that are not cancer, like infection and anemia. 

Circulating tumor cell (CTC) test:

A Circulating Tumor Cell (CTC) test is a blood test that looks for tumor cells that were shed from a tumor and are now circulating through the bloodstream. This test may be used to diagnose and monitor certain cancers, such as metastatic breast cancer, colorectal cancer, and colon cancer. Currently, CellSearch is the only FDA-approved CTC test.


Urinalysis, or urine testing, is a type of diagnostic testing that measures the components of your urine. Urinalysis breaks down the components of your urine, such as the sugars, proteins, and red and white blood cells, to check for blood, protein, and other substances. 

At times, blood in your urine can indicate cancer in the prostate, kidneys, or bladder. 

Tumor Marker tests

Tumor markers are substances in the body found in blood, urine, or body tissues. Tumor markers made by cancer cells, or normal cells, in response to cancer in the body. They are produced in higher quantities when cancer or certain benign conditions are present. 

Tumor marker tests used to diagnose cancer include:

CA-125 Test: CA-125 test measures the amount of cancer antigens in your blood. CA-125 is a protein that is a tumor marker. Then protein is found in higher concentration in cancer cells, and in particular ovarian cancer cells. 

The CA-125 Test may be used to:

  • Monitor treatment for ovarian cancer
  • Check to see if the cancer has come back after successful treatment
  • Screen women who are at high risk for ovarian cancer

Prostate-specific antigen (PSA): A prostate-specific antigen (PSA) test measures the level of PSA in the blood. PSA is a protein released by prostate tissue that is found in higher levels in blood. Though a high PSA reading does not necessarily indicate prostate cancer, an increase in PSA level over time can indicate prostate cancer. A PSA test is most useful to see if and how fast the PSA level goes up over time. 

Carcinoembryonic antigen (CEA): CEA is a protein that is usually not present in healthy adults. Though CEA is produced by cancerous cells, it can also be produced due to other conditions, such as liver disease and inflammatory bowel disease. Colorectal cancer is the most common cancer that makes this tumor marker go up.

The CEA test can also be used to monitor cancers of the:

  • Liver
  • Rectum
  • Breast
  • Pancreas
  • Stomach
  • Thyroid 

The bottom line

There are many different types of diagnostic tests for cancer. If you have signs or symptoms of cancer that are worrying you, speak with your doctor immediately. 

You can reach out to our team at any point if you have questions about your upcoming laboratory tests. Remember to check test requirements prior to your test.

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