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What Does a PSA Blood Test Show?

According to the National Cancer Institute, 15.9 percent of men born today (1 man in 6), will be diagnosed with prostate cancer sometime during his life. The PSA blood test may be able to help doctors detect and treat prostate cancer earlier, possibly resulting in the ability to save more lives. Unfortunately, there is some controversy over the usefulness of PSA blood tests. PSA tests are a useful diagnostic tool, but the test alone does not provide all the necessary answers when attempting to determine if a patient has prostate cancer.

  1. Definition

    • PSA is an acronym for prostate-specific antigen. The cells of the prostate gland produce a protein known as PSA. It is normal for some of this PSA to be found in a man's blood. If the prostate is enlarged because of a cancerous or benign tumor, the amount of PSA found in a man's blood will be higher than normal. The U.S. Food and Drug Administration has approved the PSA blood test as a tool for detecting cancer in men over the age of 50 and in men with a previous history of prostate cancer.

    Findings

    • A PSA blood test will show how many nanograms of PSA are present in 1 ml of blood. Although there is no established normal PSA level, doctors generally feel that a PSA level of less than 4 ng of PSA per ml of blood (4 ng/ML) is acceptable. If a man's PSA levels are higher than 4ng/mL, his doctor may wish to perform further testing, such as taking a urine sample or obtaining an ultrasound of the prostate. An elevated PSA level alone does not necessarily indicate cancer, so talk to your doctor if you are disturbed by the results of your PSA blood test.

    Limitations

    • As a man ages, the amount of PSA in his blood naturally increases. It has been suggested that, to make the PSA blood test more accurate, age-specific acceptable PSA levels should be developed. Unfortunately, this has not occurred. Another limitation to PSA tests is the possibility of a false-positive result. PSA levels can be elevated even when a man does not have prostate cancer. An elevated PSA level indicates cancer only 25 to 35 percent of the time. If a man has a slowly developing form of prostate cancer, it is possible for a cancerous tumor to be present, but be too small to cause a significant increase in PSA levels.

    Controversy

    • PSA blood tests are somewhat controversial. While some doctors argue that any tool that might help detect cancer is worth having, not all doctors are convinced that PSA tests provide accurate enough information to be worthwhile. False-positive PSA blood test results are common and may result in the unnecessary risk and expense of subjecting a patient to further cancer screening procedures. The best way to determine if a man has prostate cancer is to perform a prostate biopsy---a procedure that can cause both incontinence and erectile dysfunction.

    Further Study

    • The benefits of PSA blood tests are being studied by several organizations, including the National Cancer Institute, to determine whether or not these tests truly help to save lives. Other researchers are looking into ways to improve the accuracy of the information provided by PSA tests. PSA density is being examined for any possible correlation between PSA levels in the body and the size of the prostate. Researchers are also attempting to discern if the amount of change in a specific man's PSA level over time may be a more helpful measurement than the PSA levels themselves.

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