Get answers to your Genitourinary cancer questions.
Prostate-specific antigen; Prostate cancer screening test
PSA stands for prostate-specific antigen. It is a protein produced by prostate cells.
This article discusses the blood test to measure the amount of PSA in a man's blood. The PSA test is done to help diagnose and follow prostate cancer in men.
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
Men should not ejaculate for at least 48 hours before the PSA test is done. Doing so may cause a false rise in PSA levels.
Make sure your doctor knows all the medications you're taking. Some drugs may cause your PSA levels to be falsely low. These include finasteride, dutasteride, saw palmetto use, and antiandrogen drugs, such as flutamide, nilutamide, and bicalutamide.
No other special preparation is usually needed.
When the needle is inserted to draw blood, some people feel moderate pain while others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a bruise.
Reasons for a PSA test:
For information about prostate cancer screening, see the "Considerations" section below.
No certain PSA level that is called normal or abnormal. No PSA level means you do or do not have prostate cancer. Remember that the PSA test cannot diagnose cancer. Only a biopsy can diagnose cancer. Always discuss PSA test results with your doctor
Your doctor will look at your PSA results and must consider your age, your race, medicines you are taking, and a number of other factors to decide whether your PSA is normal and whether you need more tests done.
Older men typically have slightly higher PSA levels than younger men. Normal ranges by age group commonly used include:
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
A high PSA level has been linked to an increased chance of having prostate cancer. However, a high PSA level only identifies patients at higher risk of having prostate cancer.
As a general guideline, the following results indicate a need for further follow-up and testing:
Keep in mind that, although PSA testing is an important tool for detecting prostate cancer, it is not foolproof. Your doctor must also think about other factors besides cancer that may cause higher PSA values:
Your doctor will think about the following factors when deciding on the next step:
People at higher risk may need to have more tests. Next steps your doctor may take include:
For someone who has been treated for prostate cancer, the PSA level can show if a treatment is working or if the cancer has come back. Often, PSA levels will begin to rise before there are any symptoms, sometimes months or years beforehand.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
Measuring PSA levels can increase the chance of finding prostate cancer when it is very early.
However, the value of PSA screening for prostate cancer is controversial. There is not a single answer that fits all men. Before having the test, it is best to discuss both the reasons to have and the reasons not to have a PSA test with your doctor.
Some questions you may ask your doctor when discussing having a PSA test include:
If a man chooses to be tested, the PSA is most often done every year to screen:
PSA testing is not recommended for screening men over age 75.
There are different recommendations about screening tests for prostate cancer. For more information, check with:
American Urological Association.
Lin K, Lipsitz R, Miller T, Janakiraman S; U.S. Preventive Services Task Force. Benefits and harms of prostate-specific antigen screening for prostate cancer: an evidence update for the U.S. Preventive Services Task Force. Ann Intern Med. 2008;149:192-199.
Lim LS, Sherin K; ACPM Prevention Practice Committee. Screening for prostate cancer in U.S. men ACPM position statement on preventive practice. Am J Prev Med. 2008;34:164-170.
Walsh PC, DeWeese TL, Eisenberger MA. Clinical practice. Localized prostate cancer. N Engl J Med. 2007;357:2696-2705.
Walter LC, Bertenthal D, Lindquist K, Konety BR. PSA screening among elderly men with limited life expectancies. JAMA. 2006;296:2336-2342.
Wolf AM, Wender RC, Etzioni RB, Thompson IM, D'Amico AV, Volk RJ, et al. American Cancer Society guideline for the early detection of prostate cancer: update 2010. CA Cancer J Clin. 2010;60:70-98.
© 2011 University of Maryland Medical Center (UMMC). All rights reserved.
UMMC is a member of the University of Maryland Medical System,
22 S. Greene Street, Baltimore, MD 21201. TDD: 1-800-735-2258 or 1.866.408.6885