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 as a result of an injury, a digital rectal exam, sexual activity (ejaculation), inflammation of the prostate gland (prostatitis), or prostate cancer.

Prostate cancer often grows very slowly, without causing major problems. Detecting prostate cancer early and treating it may prevent some health problems and reduce the risk of dying from the cancer. However, some treatments for prostate cancer can cause other problems, such as controlling urination (incontinence) or erection problems (erectile dysfunction). Some men may choose not to have a PSA test or treat prostate cancer if it is detected. For example, a man older than age 75 who has no bothersome symptoms of prostate cancer may choose not to treat the cancer if it is found, so he would not need a PSA test.

Should I have a prostate-specific antigen (PSA) test to screen for prostate cancer?

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	Should I have a prostate-specific antigen (PSA) test to screen for prostate cancer?

Why It Is Done

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

• Watch prostate cancer and see if treatment is working. 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.
• 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.
• Check men for prostate cancer. Experts disagree on the usefulness of PSA testing as a screening tool for prostate cancer. If a PSA test is used for screening, it is usually done for men older than age 50 or for those at high risk for prostate cancer, such as men with a family history of prostate cancer, or for African-American men who have a higher chance of developing cancer than other men. Since other common medical conditions, such as prostatitis, can cause high PSA levels, a prostate biopsy is needed to confirm a diagnosis of cancer.

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 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 to drain urine recently.

Do not ejaculate during the 2 days 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 indicate. 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 to 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.
• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

A prostate-specific antigen (PSA) test measures the amount of prostate-specific antigen in the blood. Normal values may vary from lab to lab.

Normal

Because normal PSA levels seem to increase with age, age-specific ranges may be used. However, 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. This table is a reference for white males. Results for black and Asian males are slightly different.

High values

• PSA levels from 4 to 10 ng/mL: About 20% to 30% of men (20 to 30 men in 100) with PSA levels in this range may have prostate cancer. A transrectal ultrasound (TRUS) and prostate biopsy are needed to confirm a diagnosis of cancer.
• PSA levels above 10 ng/mL: About 40% to 60% of men (40 to 60 men in 100) with PSA levels in this range may have prostate cancer. A transrectal ultrasound (TRUS) and prostate biopsy are needed to confirm cancer.
• High levels do not always mean prostate cancer is present. PSA levels may be high if the prostate gland is enlarged (benign prostatic hypertrophy, or BPH) or inflamed (prostatitis).

A follow-up test, percent free prostate-specific antigen (free PSA), may be used to see if a prostate biopsy should be done to check for cancer. Men with a low percentage of free PSA have a higher chance of developing cancer as shown in the table below.

Low free PSA values (less than 15%) are more likely to be caused by prostate cancer than high free PSA values.

What Affects the Test

Factors that can interfere with your test or the accuracy of the results include:

• Recent sexual activity (ejaculation) or a cystoscopy.
• Recent use of a tube (catheter) to drain urine.
• Recent urinary tract infection (UTI) or prostatitis.
• Large doses of medicines, such as cyclophosphamide (Cytoxan, Neosar), diethylstilbestrol, and methotrexate for cancer treatment.
• The medicine finasteride, such as Proscar or Avodart, which is used to prevent further enlargement of the prostate gland in men with BPH.

What To Think About

• When combined with a digital rectal exam, the prostate-specific antigen (PSA) test increases the chance of detecting prostate cancer. For more information, see the medical test Digital Rectal Examination (DRE).
• A PSA level within the normal ranges does not mean that prostate cancer is not present. Some men with prostate cancer have normal PSA levels.
• Experts disagree about the frequency of PSA testing to screen for prostate cancer.
  • The American Cancer Society (ACS) recommends an annual PSA test and DRE for men age 50 and older. ACS also recommends annual screening, beginning at age 45, for men who are at high risk for prostate cancer, such as black men and men who have a family history of prostate cancer.
  • Other expert groups, such as the National Cancer Institute and the U.S. Preventive Services Task Force, believe there is not enough evidence to recommend routine screening with the PSA test for all men. Experts that do not recommend annual screening say the high rate of false-negative and false-positive results and the costs and risks of further tests do not support annual screening tests.
• 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 hypertrophy.
  • 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 hypertrophy).
• Complexed prostate-specific antigen (cPSA) when used in combination with a digital rectal exam can detect prostate cancer. The cPSA test currently is not widely available.

References

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.

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