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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; PSA

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

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

In most cases, no other special steps are needed to prepare for this test.

How the Test will Feel

You may feel slight pain or a prick when the needle is inserted. 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 people after prostate cancer treatment to see if the cancer has come back.
  • If a provider feels the prostate gland is not normal during physical exam.

MORE ABOUT SCREENING FOR PROSTATE CANCER

Measuring the PSA level can increase the chance of finding prostate cancer when it is very early. But there is debate over the value of the PSA test for detecting prostate cancer. No single answer fits all men.

Before having the test, talk to your provider about the pros and cons of having a PSA test. Ask about:

  • Whether screening decreases your chance of dying from prostate cancer.
  • Whether there is any harm from prostate cancer screening, such as side-effects from testing or overtreatment of cancer when discovered.

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

  • From ages 55 to 69, 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 provider 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 nanograms per milliliter (ng/ml) of blood.

  • For men in their 50s or younger, a PSA level should be below 2.5 in most cases.
  • 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
  • Recent intercourse or ejaculation

Your provider will consider 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 a prostate lump was found 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. These may include:

  • Repeating your PSA test, most often sometime within 3 months. You may receive treatment for a prostate infection first.
  • A prostate biopsy will be done if the first PSA level is high, or if the level keeps rising when the PSA is measured again.
  • 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.

Other tests may also be done. The exact role of these tests in deciding on treatment is unclear.

  • A urine test called PCA-3.
  • A blood test called the Prostate Health Index (PHI).
  • An MRI of the prostate may help identify cancer in an area of the prostate that is hard to reach during a biopsy.

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. This may happen months or years beforehand.

Risks

Slight risks associated with having blood drawn may include:

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

References

Carter HB, Albertsen PC, Barry MJ, et al. Early detection of prostate cancer: AUA Guideline. J Urol. 2013;190(2):419-426. PMID: 23659877 www.ncbi.nlm.nih.gov/pubmed/23659877.

Morgan TM, Palapattu GS, Partin AW, Wei JT. Prostate cancer tumor markers. In: Wein AJ, Kavoussi LR, Partin AW, Peters CA, eds. Campbell-Walsh Urology. 11th ed. Philadelphia, PA: Elsevier; 2016:chap 108.

National Cancer Institute. Prostate cancer screening. (health professional version). Updated April 4, 2016. www.cancer.gov/types/prostate/hp/prostate-screening-pdq. Accessed April 13, 2016.

U.S. Preventive Services Task Force. Screening for prostate cancer. Updated July, 2015. www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/prostate-cancer-screening. Accessed April 20, 2015.

Review Date:3/28/2016
Reviewed By:Scott Miller, MD, urologist in private practice in Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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