At a Glance
Why Get Tested?
To screen men for prostate cancer (although there is currently no consensus about using this test to screen asymptomatic men for prostate cancer), to help determine the necessity for a biopsy of the prostate, to monitor the effectiveness of treatment for prostate cancer, and to detect recurrence of prostate cancer
When to Get Tested?
When a man has symptoms suggestive of prostate cancer such as difficult, painful, and/or frequent urination; may also be ordered during and at regular intervals after prostate cancer treatment. There is continued debate among experts and national organizations over when and how often to order the PSA test to screen asymptomatic men. The frequency of prostate cancer screening is an individual decision that should be determined through discussion with your physician. (For specific details, see prostate cancer screening for Adults and Adults 50 and Up).
A blood sample drawn from a vein in the arm
Test Preparation Needed?
The Test Sample
What is being tested?
PSA is a protein produced primarily by cells in the prostate, a small gland that encircles the urethra in males and produces a fluid that makes up part of semen. Most of the PSA that the prostate produces is released into this fluid, but small amounts of it are also released into the bloodstream. PSA exists in two forms in the blood: free (not bound) and complexed (cPSA, bound to a protein). The most frequently used PSA test is the total PSA, which measures the sum of the free PSA and the cPSA in the blood. When a doctor orders a "PSA test," he is referring to a total PSA.
This test is used as a tumor marker to screen for and to monitor prostate cancer. It is a good tool but not a perfect one, and currently there is no consensus among experts on the usefulness of this test for screening asymptomatic men. Elevated levels of PSA are associated with prostate cancer, but they may also be seen with prostatitis and benign prostatic hyperplasia (BPH). Mild to moderately increased concentrations of PSA may be seen in those of African American heritage, and levels tend to increase in all men as they age.
PSA is not diagnostic of cancer. The gold standard for identifying prostate cancer is the prostate biopsy, collecting small samples of prostate tissue and identifying abnormal cells under the microscope. The total PSA test and digital rectal exam (DRE) are used together to help determine the need for a prostate biopsy. The goal of screening is to minimize unnecessary biopsies and to detect clinically significant prostate cancer while it is still confined to the prostate. The term clinically significant is important because while prostate cancer becomes relatively common in men as they age, many of the tumors are very slow-growing and this type of cancer is an uncommon cause of death. Doctors must try to both detect prostate cancer and to differentiate between slow-growing cases and prostate cancers that may grow aggressively and spread to other parts of the body (metastasize). Over-diagnosing and over-treatment are issues with which doctors are currently grappling. In some cases, the treatment can be worse than the cancer, with the potential for causing significant side effects, incontinence, and erectile dysfunction. The PSA test and DRE can detect most cases of prostate cancer, but they cannot, in general, predict the course of a person's disease.
Free PSA and cPSA tests can be ordered individually. The tests that measure them were developed to better differentiate between cancer-related and non-cancer-related PSA increases. Both of the tests operate on the principle that men with prostate cancer frequently have altered ratios of the two forms of PSA - decreased amounts of free PSA and increased amounts of cPSA.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
Ask a Laboratory Scientist
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
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(2012 May 29). U.S. Preventive Services Task Force Advises against PSA Screening. NCI Cancer Bulletin v9 (11). [On-line information]. Available online at http://www.cancer.gov/ncicancerbulletin/052912/page4 through http://www.cancer.gov. Accessed May 2012.
Norton, A. (2012 May 28). Doctors disagree on when to stop PSA screening. MedlinePlus Medical Encyclopedia from Reuters Health [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/news/fullstory_125648.html through http://www.nlm.nih.gov. Accessed May 2012.
(Updated 2012 March 28). National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC). Medical Tests for Prostate Problems [On-line information]. Available online at http://kidney.niddk.nih.gov/kudiseases/pubs/medtestprostate/ through http://kidney.niddk.nih.gov. Accessed May 2012.
Wiebe, C. (2012 May 29). Before PSA Screening, 'People Were Drowning.' Medscape Medical News from the American Urological Association (AUA) 2012 Annual Scientific Meeting [On-line information]. Available online at http://www.medscape.com/viewarticle/764659 through http://www.medscape.com. Accessed May 2012.
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Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 500-501.
(Updated 22 May 2012). Centers for Disease Control and Prevention. Prostate Cancer - Screening. Available online at http://www.cdc.gov/cancer/prostate/basic_info/screening.htm through http://www.cdc.gov. Accessed June 2012.
(Last Revised 5 March 2012). American Cancer Society. American Cancer Society Guidelines for the Early Detection of Cancer. Available online at http://www.cancer.org/Healthy/FindCancerEarly/CancerScreeningGuidelines/american-cancer-society-guidelines-for-the-early-detection-of-cancer through http://www.cancer.org. Accessed June 2012.
Sources Used in Previous Reviews
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(2004 May 26). Some Men with Low PSAs Have Prostate Cancer: Most Cancers Found Are Not Likely to Be Clinically Significant. NIH News [On-line Press Release]. Available online at http://www.nih.gov/news/pr/may2004/nci-26.htm through http://www.nih.gov.
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