The prostate-specific antigen blood test (PSA test) is a screening test that measures the amount of a chemical called prostate-specific antigen (PSA) in a man's blood. PSA is a chemical made by the prostate, a sex gland located near a man's bladder that makes the fluid in semen. PSA levels normally increase as a man ages, but a higher-than-normal PSA level can mean that cancer has developed in the prostate gland. However, high levels of PSA also can be found in other conditions that are noncancerous, including prostatitis (inflammation of the prostate) and benign prostatic hyperplasia, an enlargement of the prostate that affects many older men.
What It's Used For
PSA is used mainly as a screening test for cancer of the prostate. In men who have been diagnosed with prostate cancer, PSA is measured to determine if the cancer has returned after surgery or whether the cancer is growing or shrinking after treatment with hormones orradiation.
The question of whether to do screening tests for prostate cancer remains controversial. Prostate cancer is the most commonly diagnosed cancer in men in the United States and the second leading cause of cancer death in this group. PSA testing can be used to detect the earliest stage of prostate cancer, before the disease causes any symptoms. Many experts believe that PSA testing is the best way to reduce a man's chance of dying of prostate cancer. This is because the early stages of prostate cancer are much more likely to be curable.
However, other experts fear that if PSA is overused, some men will be diagnosed and treated for cancers that have little potential to cause harm. Many older men develop prostate cancer that never spreads and never causes any problems. Most of these harmless cancers would go undetected if screening was not done. Since treatment for prostate cancer can have serious side effects, screening all men for prostate cancer might end up causing more harm than good. Unfortunately, there is no reliable way to determine in advance which cancers need treatment and which are likely to be harmless.
Studies are being done that will help to settle this controversy. In the meantime, most expert panels that make recommendations about cancer screening do not recommend routine PSA testing for all older men. Instead, they encourage men who are at risk of the disease to make an individual decision about screening, after they have discussed the risks and benefits with their health care professionals.
A man who decides to undergo screening for prostate cancer might think the following:
"The PSA test is the best way to protect myself from prostate cancer. Even if it saves one life, it is worth the uncertainty and all of the possible side effects of treatment. I'm one of those people who just likes to know."
A man who chooses not to be screened might think this way:
"No one is sure if screening really helps, and it may actually lead to unnecessary treatment. I think I'll wait until we know more."
For men who want to be screened for prostate cancer, the PSA test usually is combined with adigital rectal exam. Most experts recommend that screening be done every one to two years, beginning at age 50. Men with an increased risk of prostate cancer may wish to begin screening at age 45. This includes African-American men, who have a 70 percent higher rate of prostate cancer than white men, and men whose father or brother has been diagnosed with prostate cancer.
PSA testing is likely to be less useful in men older than age 75 and men who have serious medical problems or other reasons for a limited life expectancy. This is because it may take a decade or more for prostate cancer to grow from the stage at which it can be first detected to the point where it causes symptoms or harm.
Ejaculation can cause your PSA to rise briefly, so you should avoid sexual activity for at least 48 hours before having your PSA level tested. Since blood for your PSA test probably will be taken from your arm, wear a shirt or sweater with sleeves that roll up easily. If you recently have had cystoscopy or needle biopsy of the prostate, let your doctor know so you can schedule your PSA test at another time. Those exams can raise PSA levels for a few weeks, which may make it harder to interpret the result of your PSA test. PSA testing also should not be done until several weeks after you have been treated for a urinary tract infection.
How It's Done
Blood for a PSA test usually is drawn from a vein in the crook of your elbow. The area from which blood will be taken will be cleaned with an alcohol swab, and a sterile needle will be used to draw a few ounces of blood into a tube. The puncture site will be covered with a small gauze or bandage. Your blood sample will be sent to a lab where the PSA level is measured.
Call your doctor for your PSA test results about one week after your blood has been drawn. If your result is abnormal, your doctor may recommend further blood tests or additional testing, such as a prostate ultrasound or a biopsy of the prostate.
Having your blood drawn is a simple procedure and there are few, if any, risks. However, when used as a screening test, PSA does have some risks, including:
A risk that your PSA test will be abnormal and that you will need to undergo further testing, such as a prostate biopsy. Keep in mind that as many as three-quarters of men with an elevated PSA level do not have prostate cancer. However, many men who are told that their PSA test is abnormal will have some anxiety until final results are available.
A risk that screening will lead to treatment for prostate cancer that may or may not be necessary, but that may cause serious side effects.
A risk that your PSA level will be normal even if you do have prostate cancer.
Be sure to discuss these risks and the benefits of PSA testing with your doctor before you have your blood drawn.