The PSA test is used primarily to screen for prostate cancer. A PSA test measures the amount of prostate-specific antigen (PSA) in your blood. PSA is a protein produced in the prostate, a small gland that sits below a man's bladder. PSA is mostly found in semen, which also is produced in the prostate. Small amounts of PSA ordinarily circulate in the blood.
The PSA test can detect high levels of PSA that may indicate the presence of prostate cancer. However, many other conditions, such as an enlarged or inflamed prostate, can also increase PSA levels.
Use of the PSA test is controversial. It's important to discuss with your doctor whether you should get a PSA test and what the results may mean.
Why it's done
Prostate cancer is the most common nonskin cancer in men, and it's the leading cause of cancer-related death in men. Early detection may be an important tool in getting appropriate and timely treatment.
Men with prostate cancer may have elevated levels of PSA. But many noncancerous conditions can also increase a man's PSA level. Although the PSA test can detect high levels of PSA in the blood, the test doesn't provide precise diagnostic information about the condition of the prostate.
The PSA test is only one tool used to screen for early signs of prostate cancer. Another common screening test, usually done in addition to a PSA test, is a digital rectal exam. In this test, your doctor inserts a lubricated, gloved finger into your rectum to reach the prostate. By feeling or pressing on the prostate, the doctor may be able to judge whether it has abnormal lumps or hard areas.
Neither the PSA test nor the digital rectal exam provides enough information for your doctor to diagnose prostate cancer. Abnormal results in these tests may lead your doctor to order a prostate biopsy. During this procedure, samples of tissue are removed for laboratory examination. A diagnosis of cancer is based on the biopsy results.
Other reasons for PSA tests
What you can expect
A PSA test is done by examining a blood sample in a laboratory. A nurse or medical technician will use a needle to draw blood from a vein, most likely in your arm. The site may be tender for a few hours, but you'll be able to resume most normal activities.
The risks associated with a PSA test are related to what's done in response to the information you get from the test. In other words, does the expected benefit of knowing the results of a PSA test outweigh the potential risks of knowing?
But to judge the benefit of the test, it's important to know if early detection and early treatment will improve treatment outcomes and decrease the number of deaths from prostate cancer. Most experts argue that there isn't enough evidence to answer this question.
A key issue is the typical course of prostate cancer. If all cases of prostate cancer progressed rapidly and caused poor health and death, then early detection clearly would be a good thing. However, prostate cancer usually progresses slowly over many years, and the majority of cases are diagnosed in men older than age 65. Therefore, a man may have prostate cancer that never causes symptoms or becomes a medical problem during his lifetime.
Limitations of the test
The American Cancer Society and the American College of Preventive Medicine recommend that doctors provide information about prostate cancer screening to men starting at age 50. These organizations also suggest that men in high-risk groups could benefit from this information at age 45 or 40, depending on their level of risk.
The U.S. Preventive Services Task Force recommends against PSA-based screening for men who do not have symptoms that are highly suspicious for prostate cancer. The USPSTF states that PSA testing in healthy men, regardless of age, offers no net benefit or that the harms outweigh the benefits.
The American Urological Association recommends that men talk to their doctors about getting a baseline PSA test at age 40. This could help them determine when to screen in the future and to understand possible future risk and test results.
Results of PSA tests are reported as nanograms of PSA per milliliter of blood (ng/mL). There's no specific cutoff point between a normal and abnormal PSA level. Your doctor might recommend a prostate biopsy based on results of your PSA test and a digital rectal exam, along with other factors.
Variations of the PSA test
As with the standard PSA test, there's little clinical evidence that these variations on the PSA screening test improve treatment outcomes or decrease the number of deaths. Researchers continue investigating these strategies to determine whether they provide a measurable benefit. Variations of the PSA test include:
Talk to your doctor
Discussing these issues beforehand may make it easier for you to learn the results of your test and make appropriate decisions afterward.
Last Updated: 2011-10-13
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