PSA Test
Prostate specific antigen (PSA) is a protein produced in the prostate gland that keeps semen in liquid form. Prostate cancer cells appear to produce this protein in elevated quantities. Measuring PSA levels increases the chance for detecting the presence of cancer when it is microscopic. There are many unresolved questions surrounding PSA testing. The test is not accurate enough to either completely rule out or confirm the presence of cancer. Relying too much on the test may lead to unnecessary biopsies. Not relying on it enough may miss cancers. It is still unclear if PSA testing is actually saving lives.
 | Click the icon to see an image of a PSA blood test. |
Indications for Biopsy. A biopsy is usually performed to confirm or rule out cancer after screening tests that report the following:
- PSA level of 4.0 ng/mL or higher. Some evidence indicates that men with an initial test showing PSA levels above 4.0 should take a second PSA test several weeks afterward before having a biopsy, since many non-malignant factors can increase PSA levels. (Some experts urge biopsies even if PSA levels fall below 4.0 mg, particularly in men under 60, since lower levels do not necessarily rule out cancer.)
- Abnormal digital rectal examination (DRE).
Men with abnormal results from both tests have a 60% chance of prostate cancer. The chances for cancer if only one test is abnormal are considerably lower. To further complicate matters, biopsies themselves may miss very small cancers detected by PSA levels alone.
Factors Affecting PSA Levels. A number of factors and noncancerous conditions can influence PSA levels:
- Ethnicity. Normal levels in Caucasian males may be different from those for African-American or Asian men. For example, using PSA screening, one study suggested that 15% of Caucasians and 37% of African-Americans are overdiagnosed with prostate cancer based upon PSA results. Some experts believe that there should be different scales for determining risk among these groups, but there is still not enough information to determine a specific range for various ethnic groups.
- Age. PSA levels tend to rise naturally with age, so an elevated level in a man who is 70 may be less serious than the same level in a younger man. Some experts believe that men older than 65 who have low PSA levels are at such low risk for prostate cancer that they may be able to forgo further testing.
- Benign Prostatic Hyperplasia (BPH) and Its Treatments. Between 25 - 56% of patients with BPH have elevated PSA levels. Certain treatments for this condition can also elevate PSA.
- Prostatitis. About half of men with elevated PSA levels but no signs of cancer on biopsy have signs of prostatitis as indicated by urine and prostate secretion tests. (Prostatitis simply means inflammation in the prostate. Inflammation is usually due to bacterial infection but it can also be caused by nonbacterial factors.) In one study, screening for prostatitis increased the accuracy of the PSA test significantly and reduced the number of unnecessary biopsies.
- Other Noncancerous Conditions. Other noncancerous conditions that can increase PSA levels include surgical procedures or drug treatments for BPH, acute urinary retention, digital rectal examinations, and prostate biopsies themselves.
- Ejaculation. Ejaculation within 48 hours before testing can raise PSA levels, although one study suggested that this occurs only when PSA levels were already elevated.
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