PSA Test (Prostate Specific Antigen)

  • Medical Author: Pamela I. Ellsworth, MD
  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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How is PSA test measured?

PSA is measured by a simple blood test that does not require fasting or special preparation. Since the amount of PSA in the blood is very low, detection of it requires a very sensitive type of technology (monoclonal antibody technique). The PSA protein can exist in the blood by itself (known as free PSA) or be bound with other substances (known as bound or complexed PSA). PSA is mostly bound to three substances: alpha-2-macroglobulin, alpha 1-antichymotrypsin (ACT), and albumin. Total PSA is the sum of the free and the bound forms. The total PSA is what is measured with the standard PSA test. More recently, a precursor of PSA, proenzyme PSA ([-2] proenzyme PSA), has been identified, which may be helpful in determining prostate cancer risk in men with a PSA under 10 and a normal digital rectal examination. The prostate health index (PHI) is a new approved test that measures the total PSA, free PSA, and [-2] proenzyme PSA.

What causes PSA elevation in the blood?

It is believed that elevation of PSA in the blood is due to its release into the circulation (bloodstream) because of a breakdown (disruption) of the prostate cellular architecture (structure). However, the reasons are not fully known. An elevated PSA level can occur in the setting of different prostate diseases/conditions including prostate cancer but also as a result of noncancerous causes. It is important to note that PSA is not specific to prostate cancer but to prostatic tissue, and therefore PSA elevations may indicate the presence of any kind of prostate disease. Common benign causes of PSA elevation include benign prostatic hyperplasia or BPH (an age-related, natural enlargement of the prostate, secondary to a noncancerous proliferation of prostate glandular cells), prostatitis (inflammation of the prostate), and infection. In fact, PSA elevation can also occur with prostate manipulation such as ejaculation, prostate examination (digital rectal examination), medical instrumentation (cystoscopy), urinary retention or catheter placement, and prostate biopsy. It is also thought that vigorous exercise that may affect the prostate, such as bicycle riding, can increase the PSA. It is for these reasons that patients should abstain from sex one to two days prior to PSA testing. As such, men choosing to undergo PSA testing should be aware of these important factors, which may influence results. As will be discussed shortly, age and prostate volume may also influence PSA test results.

Medically Reviewed by a Doctor on 2/1/2017

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