Prostate-specific Antigen (PSA) TestEn Español (Spanish Version)
This is a blood test that measures the amount of prostate-specific antigen (PSA) in the blood.
PSA is a protein made by the prostate (a male sex gland that makes most of the seminal fluid found in ejaculate). An elevated PSA level may be an indication of prostate cancer .
Anatomy of the Prostate
© 2008 Nucleus Medical Art, Inc.
Reasons for Procedure
PSA levels become elevated in men with prostate cancer.
A PSA test may be done for several reasons:
- To screen for prostate cancer in men aged 50 and older, or in younger men who are at increased risk for the disease
- To check the effectiveness of anti-hormonal therapies (LHRH agonists or anti-testosterone agents) in men who are being treated for prostate cancer
To determine if cancer has returned in men who have already been treated for prostate cancer
- This is when the PSA test is most accurate.
Risk Factors for Complications During the Procedure
Collecting blood from a vein carries minimal risk. Some people may develop a bruise or a small collection of blood under the skin at the site of the needle stick. This is called a hematoma. The chance of developing a hematoma are greater for people taking aspirin or other blood-thinning medications (eg, Coumadin).
What to Expect
Prior to Procedure
- Ejaculation can cause levels of PSA to rise, so avoid sexual activity for 2-3 days before testing.
- Cystoscopy , needle biopsy , and rectal exam of the prostate can elevate PSA levels. Schedule your PSA test for several weeks after any of these exams.
- Wait several weeks after successful treatment of a urinary tract infection or prostatitis (inflammation of the prostate) to have your PSA level tested.
- Medications such as finasteride and dutasteride lower PSA levels. Tell your doctor if you are taking these medications.
A blood sample is taken from a vein in your arm.
Description of the Procedure
You will roll up your sleeve and the person drawing blood will wrap an elastic band, or tourniquet, around your upper arm. He or she will clean your arm near the inside of your elbow with alcohol, and then insert a needle into your vein. A small amount of blood will be drawn into a collection tube. Pressure will be applied to the puncture site with a gauze pad or cotton ball as the needle is removed, and for several moments after. A small bandage may be placed on the puncture site. Your blood will then be sent to a laboratory for testing.
- Resume your normal sexual activity.
- If a hematoma develops, place a piece of cotton over the affected area under a well-secured bandage. Make sure the pressure is firm.
How Long Will It Take?
Drawing blood takes only a few minutes. Laboratory results are usually available within a few days or a week.
Will It Hurt?
It may hurt slightly as the needle pierces your arm.
- A small bruise or hematoma where the needle was inserted into your arm
- Lightheadedness—If this occurs, drink some juice or eat a snack.
- Rarely, lightheaded patients may faint.
Average Hospital Stay
None. A PSA test is done in your doctor’s office, a clinic, or a hospital laboratory.
PSA test results are reported as nanograms of PSA per milliliter of blood (ng/mL).
This table shows the current classification of PSA levels. (These values may change in the coming years as more information is gained regarding the differences in “normal” PSA levels for men based on their age, family history, and race.)
|Slightly elevated||4-10 ng/mL|
|Moderately elevated||10-20 ng/mL|
|Highly elevated||20 ng/mL or higher|
It is important to notice however that a value of 4 ng/mL is arbitrary. Lowering “normal values” would likely detect more cancers, but will also lead to many unnecessary biopsies. One study showed that even if the value for “normal” PSA was lowered to 1.1 ng/dL it would still miss about 17% of prostate cancers. On the other hand, another study showed that detecting cancers with low PSA levels does not really affect the cure rates.
The recommendations for follow-up after a normal PSA test result vary. You may be advised to be retested in one year, or you may be told that it is unnecessary for you to be retested for several years. It is important to note that about one-fifth of men with early prostate cancer receive normal PSA test results.
If the test reveals that your PSA level is elevated, your doctor may repeat the test. Your doctor should also do a digital rectal exam to manually check for any physical abnormalities of the prostate. PSA levels rise with age, and can also increase in response to many noncancerous conditions including benign prostate enlargement , inflammation, and infection. Only about one-third of men with an elevated PSA level have cancer. If there are no other indications of cancer, your doctor may recommend repeating the PSA test regularly to monitor changes.
If your PSA level has increased and/or the doctor notices a lump during a digital rectal exam, he or she will probably schedule diagnostic tests such as a urine test, imaging tests, x-ray , cystoscopy , or a transrectal utrasound guided needle biopsy of the prostate . Benign conditions do not cause a palpable lump in the prostate, and this is an indication for the prostate to be biopsied.
If your doctor suspects prostate cancer, a biopsy will be recommended. This is the removal of a sample of prostate tissue for testing. It is done as an outpatient procedure.
Advances in PSA Testing
There are a few modifications of PSA measurement available that hopefully will help clarify the confusion with prostate cancer screening.
- PSA density—PSA is measured and adjusted to a patient’s prostate volume to account for enlarged prostate due to BPH
- PSA velocity—measures the rate of PSA change over time with assumption that rapid increase in elevated PSA is likely to be secondary to cancer
Serum-free PSA and bound PSA—measures proportion of free PSA to total PSA
- In case of prostate cancer, free PSA is usually lower than in benign conditions.
It appears that these modifcations in PSA testing will be most useful for “gray zone” PSA levels between 4-10 ng/mL.
American Cancer Society
American Foundation for Urologic Disease
National Kidney and Urologic Diseases Information Clearinghouse, National Institutes of Health
Canadian Cancer Society
Canadian Prostate Cancer Network
Benson MC, Whang IS, Olsson CA, et al. The use of prostate specific antigen density to enhance the predictive value of intermediate levels of serum prostate specific antigen. J Urol . 1992;147:817.
Cancer facts: questions and answers about the prostate-specific antigen (PSA) test. National Cancer Institute website. Available at: http://www.cancer.gov/cancertopics/factsheet/Detection/PSA . Accessed October 25, 2007
Fang J, Metter EJ, Landis P, Carter HB. PSA velocity for assessing prostate cancer risk in men with PSA levels between 2.0 and 4.0 ng/mL. Urology . 2002;59:889.
Prostate cancer prevention and screening: know your options. Mayo Clinic website. Available at: http://www.mayoclinic.com . Accessed October 25, 2007.
Stephan C, Stroebel G, Heinau M, et al. The ratio of prostate-specific antigen (PSA) to prostate volume (PSA density) as a parameter to improve the detection of prostate carcinoma in PSA values in the range of < 4 ng/mL. Cancer . 2005;104:993.
Thompson IM, Ankerst DP, Chi C, et al. Operating characteristics of prostate-specific antigen in men with an initial PSA level of 3.0 ng/ml or lower. JAMA . 2005;294:66.
Last reviewed October 2007 by Marcin Chwistek, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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