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What is a PSA Test?

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  • Written By: A. B. Kelsey
  • Edited By: O. Wallace
  • Last Modified Date: 27 July 2018
  • Copyright Protected:
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    Conjecture Corporation
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The PSA test measures the amount of prostate-specific antigen (PSA) in a sample of a man’s blood. PSA is a protein produced primarily by cells in the prostate, the small, walnut-sized gland encircling the urethra in males. The prostate produces a fluid which energizes the sperm in semen. Most PSA is released into this fluid, but small amounts are also released into the bloodstream. Prostate-specific antigens can be detected at a low level in the blood of all healthy adult males.

The PSA test, sometimes called a prostate cancer-screening test, was developed as a tumor marker to screen for and to monitor prostate cancer. Although PSA is present in both benign and cancerous prostate cells, the cancer cells usually produce more PSA, thereby causing concern when a male has greater-than-normal PSA levels.

There are no universal guidelines for what numbers specify “normal” and “abnormal” PSA levels. However, most doctors and laboratories agree that for men over the age of forty, 2.5 or fewer nanograms of PSA per milliliter of blood is low and levels greater than 10 are high. Concentrations of total PSA between 4 and 10 is often referred to as the “gray zone.” Some doctors will recommend patients undergo a prostate biopsy, while other physicians will suggest retaking the PSA test in a year to check for significant changes.

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While the PSA test is considered a good screening tool for prostate cancer, it is far from foolproof. Elevated PSA levels can also indicate enlargement of the prostate, called benign prostatic hyperplasia (BPH), a urinary tract infection (UTI), or prostatitis, which is inflammation of the prostate. Recent sexual activity resulting in ejaculation can also raise a man’s PSA levels. Mild to moderately increased concentrations of PSA are often seen in men of African American heritage, and levels tend to increase in men of all races as they age. Prostate-specific antigens, therefore, are not specific just to prostate cancer.

The PSA test is causing a lot of controversy because it has not been proven that this test actually saves men’s lives. The PSA test is both false positive-prone and false negative-prone — meaning that sometimes men with prostate cancer will have a negative test, and sometimes men with a high PSA value will not have prostate cancer at all. Many doctors feel that the risks of performing unnecessary follow-up diagnostic tests and cancer treatments far outweigh the possible benefits of PSA screening. It is important that men talk to a trusted physician before making the decision to undergo a PSA test.

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