University of California San Francisco | About UCSF | UCSF Benioff Children's Hospital San Francisco
Search Site | Find a Doctor

PSA

Definition

PSA stands for prostate-specific antigen. It is a protein found in prostate cells. It can be detected at a low level in the blood of all adult men.

This article discusses the blood test to measure the amount of PSA in a man's blood.

Alternative Names

Prostate-specific antigen; Prostate cancer screening test

How the test is performed

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.

How to prepare for the test

No special preparation is usually needed.

How the test will feel

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.

Why the test is performed

This test is done to screen for prostate cancer. It is also used to monitor patients after prostate cancer treatment.

Several conditions besides cancer can cause the PSA level to rise, including:

  • Benign prostatic hyperplasia
  • Prostatitis
  • Recent catheterization or cystoscopy
  • Urinary tract infections

Discuss with your doctor or health care provider whether a PSA test is appropriate for you.

Normal Values

Normal values vary with age. Older men typically have slightly higher PSA measurements than younger men. Men with a larger prostate will also have higher PSA values.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

A high PSA level has been linked to an increased chance of having prostate cancer. However, a high PSA level does not mean that you definitely have prostate cancer. A high PSA level only identifies patients at higher risk of having prostate cancer. People at higher risk may need to have more tests.

A PSA of 4 nanograms per milliliter (ng/mL) is abnormally high for most men and may indicate the need for a prostate biopsy. For men under age 50, levels above 2 ng/mL may be too high. A significant rise from one year to the next may also indicate a higher risk of having prostate cancer.

Keep in mind that although PSA testing is an important tool for detecting prostate cancer, it is not foolproof.

Greater-than-normal PSA levels may indicate:

  • Benign prostatic hypertrophy
  • Prostate cancer
  • Prostate infection (prostatitis)
  • Urinary tract infection

What the risks are

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:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

Special considerations

Discuss the benefits and risks of testing with your doctor to determine whether screening is right for you.

  • Potential benefits include early diagnosis of cancer
  • Potential risks include increased health care costs, unnecessary invasive testing (biopsy) and treatment

The American Urologic Association, American Cancer Society, and National Comprehensive Cancer Network recommend that:

  • All men ages 40 - 75 have annual PSA tests
  • Screening should also include a prostate examination by your doctor

However, these guidelines are not recommended for everyone. Many health organizations, including the US Preventive Services Task Force, do not recommend routine PSA testing.

References

American Urological Association. Prostate-specific antigen best practice statement: 2009 update. April 2009. Accessed July 10, 2009.

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.

Review Date: 8/10/2009

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright ©2010 A.D.A.M., Inc., as modified by University of California San Francisco. Any duplication or distribution of the information contained herein is strictly prohibited.

Information developed by A.D.A.M., Inc. regarding tests and test results may not directly correspond with information provided by UCSF Medical Center. Please discuss with your doctor any questions or concerns you may have.