The PSA test is a blood test that is used to screen for the presence of prostate cancer. Prostate specific antigen is a protein found in the fluid portion of blood, called serum. PSA is specific to the prostate. No other human tissue or body part can make it. PSA levels can be measured in an individual's serum. With this information, doctors are able to screen for prostate cancer.
PSA is only present in men. PSA is present in all normal prostate tissue. The normal prostate cell holds onto most of the PSA. Very little leaks into the bloodstream. The small amount that leaks out is what is measured by the blood test. Prostate cancer cells actually have less PSA in each cell. However, the cancer cell tends to leak more PSA into the bloodstream. Knowing this fact, experts developed a range of expected values in patients with a normal prostate gland. The PSA value should be less than 4.0. This number reflects the belief that most men, roughly 95%, with normal prostate glands have a PSA value of 4.0 or less. (See below for age-specific normal values.) Almost any condition that affects the prostate can make the PSA rise.
The American Cancer Society and the American Urological Association recommend that men over age 50 have a yearly PSA. They should also have a rectal examination of the prostate. High-risk groups should begin screening at age 40 to 45. Men with a family history of the disease and African Americans fall into this category.
A simple blood test is all that is needed.
If possible, the patient should not ejaculate for 48 hours before a PSA test. If ejaculation has occurred and the PSA is elevated, it might be necessary to repeat the test.
Infections or inflammation of the prostate gland, called prostatitis, can also elevate PSA levels. Therefore, patients need to inform their doctors of any urinary symptoms that might exist. These may include pain with urination, urgency to urinate or discharge from the penis. The inflammation from prostatitis causes PSA to leak into the bloodstream. This causes the PSA level to be higher than normal.
Some patients will experience a rise in PSA if the test is taken after a simple rectal exam. If this is the case, the PSA test may have to be repeated.
The most common noncancerous cause of elevated PSA levels is benign prostate hyperplasia (BPH). As men age, the prostate normally enlarges. This becomes more apparent after age 50. The most common symptom with BPH is difficulty urinating. About 80% of men will develop some symptoms of BPH in their lifetime. BPH is not cancer and will not lead to cancer. However, BPH may cause a false elevation of PSA values.
When evaluating PSA results, the doctor must also take into account the results of the rectal exam, the patient's age, previous PSA results, and prostatic size. For example, findings on a rectal exam must be looked into even if the PSA result is normal.
Recent studies have suggested that the 4.0 level may be too high for younger men and too low for older men. Many researchers now use the following levels rather than the 4.0 used in the past. However, more time is needed to assure that these levels are more accurate.
If the rectal exam is normal then the following recommendations are suggested:
If previous PSA values are available, test results will be evaluated differently. The PSA level almost always rises if cancer is growing. Any PSA level that is rising is suspicious. However, a high PSA level may not mean that cancer is present. For example, a male with a stable PSA of 8 over a three-year period (8,8,8) is probably at less risk than a male with a PSA of 2, 4, and 6 over the same time frame. This is because the second patient's rising levels suggest growth. This makes it suspicious for cancer. If the first patient had a negative biopsy when the first high PSA value occurred, there may be no need to repeat the biopsies. If the PSA level jumped to 10 or 15 for no apparent reason, then repeat ultrasound and biopsies would be called for. Recent studies suggest that either a 20% rise or a measurable rise of 0.75 in PSA in one year should prompt a closer look. Ultrasound and biopsy may be needed.
Author:David T. Moran, MD
Reviewer:Eileen McLaughlin, RN, BSN