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PSA Test Types

In men, the prostate gland is responsible for keeping seminal fluid in the liquid state. Prostate Specific Antigen (PSA) is the protein that performs this function. PSA is used to detect prostate cancer because a tumor in the prostate gland causes PSA, which is mostly contained within the prostate gland itself, to be released into the bloodstream. The higher the level of PSA in the bloodstream, the more evidence that the cancer is more advanced and is causing the prostate gland to malfunction. There are several different types of PSA tests available.

  1. PSA Test

    • The initial test for suspected prostate trouble is the PSA test. This is a blood test using a method of determining the amount of PSA in the bloodstream. This method is called radioimmunoassay. Antibodies will attach themselves to the PSA molecules, then the technician can measure how many antibodies there are. Since the antibodies are attached to the PSA molecules, it gives an accurate count of the PSA level.

    PSA Velocity Test

    • This test is used to track the PSA level over a specified time period, either one or two years. It is repeated two or three times during that time. The PSA velocity means the increasing rate of the level of PSA in the bloodstream. If the rate has gone up more than .75 percent in a year, cancer is likely. Doctors order this test after a patient has already had a biopsy. The results let the doctor know if another biopsy needs to be done.

    PSA Density Test

    • The PSA Density Test is done to figure a ratio using the prostate size and the PSA level. Doctors will generally use this test to determine if a patient has cancer or another problem by seeing if the PSA level detected is normal for the size of the prostate. Cancer creates a higher PSA level, so the density measured should be much higher if there is cancer present.

    Free PSA Ratio

    • PSA in the bloodstream is detectable in two types; bound and free. Bound simply means that the PSA molecule is attached to an antibody or other protein, while a free PSA molecule is not attached to anything. In cases of cancer, a man will have far greater amounts of bound PSA, more than 85 percent means cancer is likely. If there is more free PSA than bound PSA, cancer is not considered likely.

    Age-specific PSA test

    • A test that takes age into consideration is used to see if younger men could have cancer. The PSA level tends to increase as a man ages, so if a younger man is tested and his PSA level is that of an older man, cancer is suspected as the cause of the higher than normal PSA.

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