PSA Test Procedures

A prostate-specific antigen (PSA) test is primarily used as early screening for prostate cancer before symptoms of the disease appear. The test measures the blood levels of the protein produced by cells of the prostate gland. Prostate cancer is not the only condition that causes PSA levels to be elevated, and elevated PSA levels alone are not enough reason to diagnose prostate cancer.

• Older men should have their prostate checked.

Who Should Be Tested?

• Doctors' recommendations on who should be tested vary, but the Food and Drug Administration has approved the use of the test to screen men over 50 for prostate cancer and to monitor their PSA levels after treatment for prostate cancer to check for recurrence of the cancer. However, the test is controversial because it is not yet known if it actually saves lives or whether its risks outweigh its benefits. Prostate biopsy can produce bleeding and infection, and prostate cancer treatment can result in complications including incontinence and impotence. The benefits and risks of this and other prostate cancer tests and treatment of prostate cancer should be taken into account when deciding whether to get a PSA test.

How Is the Test Done?

• The PSA test is a blood test. A laboratory technician or other medical practitioner will insert a needle into a blood vessel and withdraw a vial of blood for the test. If the blood sample reveals an elevated PSA level, the test will likely be followed with a digital rectal exam in which the doctor will insert a finger into the rectum to feel the prostate for enlargement or lumps.

How Are Results Expressed?

• The level of PSA in the blood is usually reported as nanograms per milliliter (ng/mL), but there is no consensus on normal or abnormal levels. Doctors generally consider 4.0 ng/mL to be normal, but prostate cancer has been diagnosed in men with PSA levels below 4.0 ng/mL, and men with PSA levels above the 4.0 ng/mL benchmark have been found to be cancer-free upon further testing. Furthermore, PSA levels are known to increase with age. Because of these factors, a single PSA test showing more than 4.0 ng/mL does not necessarily mean a biopsy is needed. The doctor might decide to take a "wait and get a later test" approach.

Limitations of the Test

• Small, slow-growing prostate tumors might never become life-threatening, so detecting them does not necessarily extend the patient's life. Also, PSA tests don't help a man with an aggressive tumor that has already spread to other parts of the body before being detected. Between 65 and 75 percent of men with an elevated PSA level who get a biopsy turn out not to have cancer, meaning the PSA level is elevated for a different reason, but further testing for cancer adds risks, costs and anxiety for the patient.

Can the PSA Test Be Improved?

• The National Cancer Institute reports that scientists are studying ways to improve the PSA test, in hopes of being better able to distinguish between cancerous and benign conditions and between slow-growing and aggressive cancers. In addition, different tests altogether are being researched for their potential to detect prostate cancer either alone or in conjunction with the PSA test.