Prostate-Specific Antigen (PSA)
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 often grows very slowly, without causing major problems. Finding prostate cancer early and treating it may prevent some health problems and reduce the risk of dying from the cancer. But some treatments for prostate cancer can cause other problems, such as being unable to control urination (incontinence) or erection problems (erectile dysfunction). Some men may choose not to have a PSA test or treat prostate cancer if it is found. 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.
- 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. Experts agree that PSA testing is not right for all men. 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 benign prostatic hyperplasia (BPH) and prostatitis, can cause high PSA levels, a prostate biopsy is needed to confirm a diagnosis of 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 to drain urine recently.
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 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.
Screening tests aren't perfect. They may miss some cancers, show something that looks like a tumor when it's not one, or find cancers that will never cause a problem. Since there is no way to know which ones will cause harm, cancers are usually treated. This may lead to unnecessary cancer treatments, such as surgery, chemotherapy, or radiation.
Talk to your doctor about whether you should have this screening test. It is important to know the risks of having this test and whether studies show that having the test will reduce your risk of dying from this kind of cancer.
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.
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.
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.
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 prostate-specific antigen that is not attached to proteins in the blood. The lower a man's free PSA level, the more likely he is to develop prostate cancer.
Free prostate-specific antigen (fPSA)
Percent free PSA
Probability of cancer
More than 25%:
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
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. For more information, see the topic Digital Rectal Examination (DRE).
- 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.
- The American Cancer Society (ACS) advises men to talk with their doctors about testing and treatment before deciding about testing. The ACS says that men should not be tested without learning about the risks and benefits. The ACS advises talking to a doctor about testing:
- At age 50 for men who are at average risk of getting prostate cancer and are expected to live at least 10 more years.
- At age 45 for men at high risk, such as African Americans and men who have a first-degree relative (father, brother, or son) who had prostate cancer when he was younger than 65.
- At age 40 for men at an even higher risk, such as those with several first-degree relatives who had prostate cancer at an early age.
- The U.S. Preventive Services Task Force (USPSTF) advises doctors about when to test for prostate cancer:
- No testing is advised for men age 75 and older.
- Before any tests, it is important for men younger than 75 to talk with a doctor about the pros and cons of PSA testing.
- Men younger than 75 who have long-term medical problems and who are expected to live less than 10 years are not likely to benefit from testing.
- The American Urological Association (AUA) recommends that men decide with their doctors about screening. If a man decides to be screened, the AUA says he should start at the age of 40 for a "baseline" score (a baseline score is a PSA level that can be used to compare with future test scores).
- Some experts do not advise yearly testing. They say the high rate of false-negative and false-positive results and the costs and risks of further tests outweigh the benefits of yearly 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 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.
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 (2008). Screening for Prostate Cancer: Clinical Summary of a U.S. Preventive Services Task Force Recommendation. Rockville, MD: Agency for Healthcare Research and Quality. Available online: http://www.ahrq.gov/clinic/uspstf08/prostate/prostaters.htm.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||Christopher G. Wood, MD, FACS - Urology, Oncology|
|Last Revised||January 31, 2011|