Prostate-Specific Antigen (PSA)

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Test Overview

A prostate-specific antigen (PSA) test measures the amount of prostate-specific antigen in the blood. PSA is released into a man's blood by his prostate gland. Healthy men have low amounts of PSA in the blood. The amount of PSA in the blood normally increases as a man's prostate enlarges with age. PSA may increase because of inflammation of the prostate gland (prostatitis) or prostate cancer. An injury, a digital rectal exam, or sexual activity (ejaculation) may also briefly raise PSA levels.

Prostate Cancer Screening: Should I Have a PSA Test?

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Why It Is Done

The prostate-specific antigen (PSA) test is done to:

  • Screen men for prostate cancer. Since other common medical conditions, such as benign prostatic hyperplasia (BPH) and prostatitis, can cause high PSA levels, a prostate biopsy may be done if your doctor is concerned about signs of prostate cancer.
  • Check if cancer may be present when results from other tests, such as a digital rectal exam, are not normal. A PSA test does not diagnose cancer, but it can be used along with other tests to determine if cancer is present.
  • Watch prostate cancer during active surveillance or other treatment. If PSA levels increase, the cancer may be growing or spreading. PSA is usually not present in a man who has had his prostate gland removed. A PSA level that rises after prostate removal may mean the cancer has returned or has spread.

How To Prepare

Before you have a prostate-specific antigen (PSA), tell your doctor if you have had a:

  • Test to look at your bladder (cystoscopy) in the past several weeks.
  • Prostate needle biopsy or prostate surgery in the past several weeks.
  • Digital rectal exam in the past several weeks.
  • Prostate infection (prostatitis) or an urinary tract infection (UTI) that has not gone away.
  • Tube (catheter) inserted into your bladder recently to drain urine.

Do not ejaculate for 24 hours before your PSA blood test, either during sex or masturbation.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

The health professional taking a sample of your blood will:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Attach a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure on the site and then a bandage.

How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

There is very little chance of a problem from having a blood sample taken from a vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.

Results

A prostate-specific antigen (PSA) test measures the amount of prostate-specific antigen in the blood.

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Normal

Because normal PSA levels seem to increase with age, age-specific ranges may be used. But the use of age-specific ranges is controversial, and some doctors prefer to use one range for all ages. For this reason, it is important to discuss your test results with your doctor.

Total prostate-specific antigen (PSA)footnote 1

Men ages 40-49:

0-2.5 nanograms per milliliter (ng/mL)

0-2.5 micrograms per liter (mcg/L)

Men ages 50-59:

0-3.5 ng/mL

0-3.5 mcg/L

Men ages 60-69:

0-5.5 ng/mL

0-5.5 mcg/L

Men ages 70 and older:

0-6.5 ng/mL

0-6.5 mcg/L

A PSA level within the normal ranges does not mean that prostate cancer is not present. Some men who have prostate cancer have normal PSA levels.

High values

High levels do not always mean prostate cancer is present. PSA levels may be high if the prostate gland is enlarged (benign prostatic hyperplasia, or BPH) or inflamed (prostatitis).

A follow-up test that measures free prostate-specific antigen (free PSA) may be used to see if a prostate biopsy should be done to check for cancer. Free PSA is the percent of prostate-specific antigen that is not attached to proteins in the blood. The lower a man's free PSA percentage, the more likely he is to have prostate cancer.

A man with a total PSA between 4 and 10 ng/mL may have a test to find out his free PSA, to see if cancer is likely to be present. This test can be very useful if he had a negative prostate biopsy in the past but still has a high total PSA.

Free prostate-specific antigen (fPSA)footnote 2

Percent of free PSA

Probability of cancer

More than 25%:

8%

20%-25%:

16%

15%-20%:

20%

10%-15%:

28%

0%-10%:

56%

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Recent sexual activity (ejaculation).
  • Recent use of a tube (catheter) to drain urine or a cystoscopy.
  • Recent urinary tract infection (UTI) or prostatitis.
  • Recent digital rectal exam, prostate biopsy, or prostate surgery.
  • Large doses of medicines, such as cyclophosphamide (Cytoxan) and methotrexate for cancer treatment.
  • The medicines dutasteride (Avodart) and finasteride (Proscar), which are used to prevent further enlargement of the prostate gland in men who have BPH, or the type of finasteride (Propecia) that is used for male-pattern baldness.

What To Think About

  • When combined with a digital rectal exam, the prostate-specific antigen (PSA) test may increase the chance of finding prostate cancer. To learn more, see the topic Digital Rectal Examination (DRE).
  • Experts disagree about the type of testing that is appropriate if the PSA level is high. The decision may depend on:
    • Results of your digital rectal exam.
    • Results of any PSA tests you have had in the past. If your PSA level gets higher in a short amount of time, follow-up testing may be recommended.
    • Your age and health.
    • The costs and risks of more tests and treatments.
  • Other prostate tests are being evaluated to determine how well they tell the difference between prostate cancer and benign prostatic hyperplasia.
    • The prostate-specific antigen density (PSAD) test compares the PSA value to the size of the prostate gland. The size of the prostate is measured using transrectal ultrasound (TRUS).
    • The PSA velocity test is a measure of how rapidly PSA levels increase over time. PSA levels increase more rapidly in men with prostate cancer and more slowly in men with prostate enlargement (benign prostatic hyperplasia).
    • A complexed prostate-specific antigen (cPSA) test may help show if a prostate biopsy should be done. This test measures the amount of several forms of PSA that are attached to proteins found in the blood.

References

Citations

  1. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
  2. Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
  • U.S. Preventive Services Task Force (2012). Screening for Prostate Cancer: Recommendation Statement. Available online: http://www.uspreventiveservicestaskforce.org/prostatecancerscreening/prostatefinalrs.htm.

Credits

ByHealthwise Staff

Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine

Kathleen Romito, MD - Family Medicine

Specialist Medical ReviewerChristopher G. Wood, MD, FACS - Urology, Oncology

Current as ofMay 3, 2017

Current as of: May 3, 2017

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Kathleen Romito, MD - Family Medicine & Christopher G. Wood, MD, FACS - Urology, Oncology