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Fasting for the PSA Blood Test: Why It is Done and How Long to Do It

written by: Leigh A. Zaykoski • edited by: Donna Cosmato • updated: 3/24/2009

The fasting PSA blood test is a lab test used to screen men for prostate cancer. If you have prostate cancer risk factors or are over the age of 50, talk with your doctor about this test to see if you need to have it done.

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    Prostate cancer screening is important for early detection of prostate tumors and cancerous cells. One of the tools used in prostate cancer screening is the PSA blood test, which measures the level of prostate specific antigen in the blood. It is a simple blood test that involves giving a sample of blood from a vein in the arm and having it analyzed by laboratory professionals. The results can help medical professionals determine if additional testing is needed.

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    Screening Guidelines

    There are no official guidelines for routine screening at this point in time. Major health organizations including the Centers for Disease Control do not recommend routine screening. In contrast, the American Cancer Society recommends that the PSA blood test be made available to all men once they have reached 50 years of age. Additionally, the American Cancer Society recommends that men who are at a higher risk of developing prostate cancer get the fasting PSA blood test beginning when they are 40 or 45. The reason for the controversy over screening guidelines is that doctors are worried about overdiagnosing prostate cancer. However, this concern must be weighed against the risk of missing a diagnosis of aggressive prostate cancer.

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    PSA Blood Test: Total and Free PSA

    The total PSA and free PSA are two separate blood tests. The total PSA blood test is ordered when someone exhibits symptoms that can indicate the presence of prostate cancer. These symptoms can include pelvic pain, frequent urination, painful urination, and low back pain. The free fasting PSA blood test is usually ordered only if a total PSA blood test result is elevated and the patient does not exhibit signs of a disease other than prostate cancer. The total PSA blood test may also be ordered once someone has been diagnosed with prostate cancer so doctors can monitor the effectiveness of the cancer treatment.

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    Fasting PSA Blood Test Results

    Normal PSA blood test results are below 4.0 ng/ml. While some feel the threshold should be reduced to 2.5 ng/ml, this could lead to overdiagnosis and overtreatment of prostate cancer that is not considered clinically significant. If a patient's elevated PSA is greater than 10.0 ng/ml, their risk for prostate cancer is increased. Levels ranging from 4 to 10 ng/ml give someone a 25% chance of developing prostate cancer.

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    Improving the Fasting PSA Blood Test

    Improving the PSA blood test will go a long way toward helping doctors diagnose aggressive cancers earlier without overdiagnosing prostate cancer. While none of the methods used to improve the test are widely accepted at this time, some doctors use them to make better diagnostic decisions. The PSA velocity measures how the concentrations of PSA in the blood change over a set period of time. If someone's PSA level rises rapidly, they may have an aggressive form of prostate cancer. PSA doubling time measures how quickly the concentrate of PSA in the blood doubles. This is a variation of the PSA velocity measurement. It has also thought that since PSA levels rise with age, that age-specific PSA ranges should be developed.

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    Further Information on the PSA Blood Test

    For information on the fasting PSA blood test, visit Lab Tests Online's PSA Guide.

    For more information on prostate cancer and screening, check out these Bright Hub Medical Science articles:

    Cancer Screening Recommendations: Prostate, Testicular, and Skin Cancers

    Treatment Options for Prostate Cancer

    Blood Testing and You: The PSA Blood Test