The prostate-specific antigen (PSA) test measures the amount of PSA a man has in his blood, reported as nanograms of PSA per ml. The cells of the prostate produce PSA, a type of protein. Some doctors use PSA tests to screen for prostate cancer or monitor patients who have had prostate cancer. High levels of PSA may indicate an increased risk of prostate cancer, which kills about 3 percent of American men. However, this test is controversial, and some doctors do not recommend PSA testing.
PSA Test Basics
During the PSA test, a nurse or doctor wraps an elastic band around your arm to force your veins to fill with blood. She then draws blood from a vein, such as the vein on the inside of your elbow or on the back of your hand, and applies a bandage afterward. You may experience a stinging pain and bruising. You can resume all normal activities after the test.
Before Your Test
Do not ejaculate within 24 hours of a PSA test, because this may artificially increase your PSA levels, according to the National Cancer Institute. Riding a bicycle or motorcycle before your test may also distort your PSA levels, because these activities put pressure on the prostate.
Digital Rectal Exams
A digital rectum exam, or DRE, refers to another screening test for prostate cancer in which a doctor places a gloved finger into the rectum to feel the prostate. Abnormalities, such as bumps, may indicate an increased risk of cancer. A DRE may also disturb the prostate gland and distort your PSA results. Ask your doctor whether you can have the PSA test before your DRE.
Other factors out of your control may affect your PSA levels. For example, having a prostate infection or urinary tract infection may temporarily change your PSA levels. Having your bladder or prostate tested or having a catheter in your bladder also affects your PSA levels. PSA levels typically rise with age. In addition, some medications, such as finasteride or hormone therapy, may artificially decrease PSA levels. Always tell your doctor about any medications you are taking.
Doctors disagree about the value of PSA tests. There is no normal PSA level or range -- cancer sometimes occurs in men who have low PSA levels, while many men with high PSA levels are healthy. Most men who have an elevated PSA do not have prostate cancer. In addition, some slow-growing prostate cancers may not be dangerous, and treating these cancers may be unnecessary. Treatment for prostate cancer often involves severe side effects that diminish a patient's quality of life, including impotence and incontinence.