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Prostate-specific antigen (PSA) blood test

Definition

Prostate-specific antigen (PSA) is a protein produced by prostate cells.

The PSA test is done to help diagnose and follow prostate cancer in men.

Alternative Names

Prostate-specific antigen; Prostate cancer screening test 

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

Make sure your doctor knows all the medicines you are taking. Some drugs cause your PSA level to be falsely low.

No other special preparation is usually needed.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a slight bruise. These soon go away.

Why the Test is Performed

Reasons for a PSA test:

  • This test may be done to screen for prostate cancer.
  • It is also used to follow patients after prostate cancer treatment to see if the cancer has come back.
  • If a healthcare provider feels the prostate gland is not normal during physical exam

Measuring the PSA level can increase the chance of finding prostate cancer when it is very early. But the value of PSA screening for prostate cancer is debated. No single answer fits all men.

Before having the test, discuss with your doctor both the reasons to have and not to have a PSA test.

If you choose to be tested, the PSA is most often done every year to screen men:

  • Age 50 to 75, if no risk factors are present.
  • Starting around age 40 to 45 if they have a higher chance of developing prostate cancer. A family history of prostate cancer (especially a brother or father) and being African-American are more common risk factors.

Normal Results

The PSA test result cannot diagnose prostate cancer. Only a prostate biopsy can diagnose this cancer.

Your doctor will look at your PSA result and consider your age, ethnicity, medicines you are taking, and other things to decide whether your PSA is normal and whether you need more tests.

A normal PSA level is considered to be 4.0 ng/ml (nanograms per milliliter of blood).

  • For men in their 50s or younger, a PSA level should usually be below 2.5.
  • Older men often have slightly higher PSA levels than younger men.

What Abnormal Results Mean

A high PSA level has been linked to an increased chance of having prostate cancer.

PSA testing is an important tool for detecting prostate cancer, but it is not foolproof. Other conditions can cause a rise in PSA, including:

  • A larger prostate
  • Prostate infection (prostatitis)
  • Urinary tract infection
  • Recent tests on your bladder (cystoscopy) or prostate (biopsy)
  • Catheter tube recently placed into your bladder to drain urine

Your doctor will think about the following things when deciding on the next step:

  • Your age
  • If you had a PSA test in the past and how much and how fast your PSA level has changed
  • If your doctor finds a prostate lump during your exam
  • Other symptoms you may have
  • Other risk factors for prostate cancer, such as ethnicity and family history

Men at high risk may need to have more tests. Your doctor may recommend:

  • Repeating your PSA test, most often sometime within 3 months
  • A prostate biopsy
  • A follow-up test called a free PSA (fPSA). The lower the level of this test, the more likely it is that prostate cancer is present.
  • A urine test called PCA-3

If you have been treated for prostate cancer, the PSA level can show if treatment is working or if the cancer has come back. Often, PSA level rises before there are any symptoms, sometimes months or years beforehand.

Risks

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)

References

American Urological Association Education and Research, Inc. PSA testing for the pretreatment staging and posttreatment management of prostate cancer: 2013 Revision of 2009 Best Practice Statement. Linthicum, MD: American Urological Association Education and Research, Inc. 2013. Available at: http://www.auanet.org/common/pdf/education/clinical-guidance/Prostate-Specific-Antigen.pdf. Accessed October 2, 2013.

Getzenberg RH, Partin AW. Prostate cancer tumor markers. In: Wein AJ, Kavoussi LR, Novick AC, et al., eds. Campbell-Walsh Urology. 10th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 98.

U.S. Preventive Services Task Force. Screening for prostate cancer. Available at: http://www.uspreventiveservicestaskforce.org/prostatecancerscreening/prostatefinalrs.htm. Accessed July 26, 2013.


Review Date: 10/2/2013
Reviewed By: Scott Miller, MD, Urologist in private practice in Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.
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