Mayo Clinicians Explain the Options.

• Position: CANCER TESTING

If it is suspected that you have cancer, your doctor likely will order certain blood or other laboratory tests, such as an analysis of your urine or a biopsy of a suspicious area, to help guide the diagnosis, explains the staff at the Mayo Clinic, Rochester, Minn.

With the exception of blood cancers, blood tests generally cannot absolutely tell whether you have cancer or some other noncancerous condition, but they can give your physician clues about what is going on inside your body.

Samples collected for cancer blood tests are analyzed in a lab for signs of cancer. They may show cancer cells, proteins, or other substances made by the cancer. Blood tests also can provide your physician with an idea of how well your organs are functioning and if they have been affected by cancer.

Examples of blood tests used to diagnose cancer include:

Complete blood count (CBC). This common blood test measures the amount of various types of blood cells in a sample of your blood. Blood cancers may be detected using this test if too many or too few of a type of blood cell or abnormal cells are found. A bone marrow biopsy may help confirm a diagnosis of a blood cancer.

Blood protein testing. A test to examine various proteins in your blood (electrophoresis) can aid in detecting certain abnormal immune system proteins (immunoglobulins) that sometimes are elevated in people with multiple myeloma. Other tests, such as a bone marrow biopsy, are used to confirm a suspected diagnosis.

Tumor marker tests. Tumor markers are chemicals made by tumor cells that can be detected in your blood, but tumor markers also are produced by some normal cells in the body, and levels may be elevated significantly in noncancerous conditions. This limits the potential for tumor marker tests to help in diagnosing cancer. The best way to use tumor markers in diagnosing cancer has not been determined, and the use of some tumor marker...