What is the PSA?


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What is the PSA and what does it mean? PSA stands for prostate specific antigen, which is a protein produced by the prostate gland.  The function of the PSA is to liquefy the semen to make it easier for sperm to swim. The PSA test measures the amount of PSA in a man’s blood.

What are the types of PSA?

You may be surprised to learn there are three types of PSA:

  • a form that is bound to alpha-1-antichymotrypsin, a protein that is associated with inflammation
  • a free form that is not bound to anything
  • a form that is surrounded by alpha-2-macroglobulin, a large protein. This form is not detectable when you are tested for PSA levels

When you have your PSA levels checked, your doctor will give you two figures: total PSA and free PSA. Generally, the higher your total PSA and lower your free PSA, the greater risk you have of developing prostate cancer. For example, if your total PSA is 4.0 to 10.0 ng/mL and your free:total PSA ratio is 0.10 or less, then you have 49% to 65% risk of developing prostate cancer. If, however, your free:total PSA ratio is greater than 0.25, your risk of getting prostate cancer is about 9% to 16%. A man’s age also plays a role in these risks.

Several conditions can raise a man’s PSA. An elevated PSA can be a sign of prostate cancer or other conditions. High PSA is commonly associated with benign conditions such as prostatitis (inflammation of the prostate) and benign prostatic hyperplasia (BPH), which is enlargement of the prostate. Other conditions can temporarily affect PSA levels such as catheterization and ejaculation.

PSA testing has become more controversial due to some of the false positives and false negatives resulting from the test. The PSA test cannot tell if a prostate cancer is slow growing or life threatening.

What is the PSA?–guidelines for the PSA test

Both the American Urological Association (AUA) and the USPSTF have recently changed their guidelines for the PSA screening for men who have not previously been diagnosed with or have had prostate cancer. What is the PSA test guideline change?

Men at higher risk due to race (African American descent) or family history should discuss screening with their doctor for “shared decision making.”

  • Men of average risk do not need to be screened before age 40.
  • Men of average risk who are between 40 and 54 also do not require testing.
  • For men between 54 and 70, screening is recommended every other year to avoid false positives.
  • Men above 70 who are in excellent health may continue screening.
  • Screening is not recommended for men who have life expectancies of less than 10 to 15 years.

Talk to your doctor to determine if you fall under any high-risk groups and be informed of the risks of prostate biopsy and other treatments that may be suggested if you are found to have an elevated PSA value.

What else you should know about the PSA test

Although the PSA test is not ideal for screening for prostate cancer and the guidelines are somewhat controversial, until more accurate and sophisticated screening tools are available, you should ask for the test based on the recommended guidelines or if you are experiencing urinary tract symptoms typically associated with prostate cancer, prostatitis, and an enlarged prostate (benign prostatic hyperplasia).

Taking a PSA test involves nothing more than a simple blood test. However, before you get the test, you should avoid the following activities 48 hours prior, because they can have an impact on your results:

  • A digital rectal exam
  • Prostate massage
  • Sexual activity that involves ejaculation
  • Vigorous activities or exercise that impact the prostate area, such as riding a horse, motorcycle, ATV, bicycle, or tractor

Related: What Not To Do Before A PSA Test

In addition, do not schedule the PSA test until at least six weeks after undergoing transurethral resection of the prostate, prostate biopsy, cystoscopy, urethral catheter, or any procedure that involves the prostate, as well as treatment with antibiotics. If you have prostatitis, talk to your doctor before you undergo a PSA test.

Related: Understanding The PSA Test For Prostate Cancer

What is PSA velocity?

In addition to values for both total and free PSA, your doctor may talk about PSA velocity. This is a measurement your doctor will take over time–typically several years–to determine how quickly your PSA values change. Identifying PSA velocity can be helpful during the early stages of prostate cancer in men who have mildly elevated PSA levels and normal digital rectal exam results.

The results of one study found that an increase in PSA levels of more than 0.75 ng/L per year was an early sign of prostate cancer among men who had a PSA level between 4 ng/L and 10 ng/mL. Yet another study noted that a rapid rise in PSA (greater than 2.0 ng/mL) over one year before men were diagnosed with prostate cancer or who had surgery was predictive of a higher chance that they would die of the disease during the next seven years.

Related: 10 Things That Can Lower Your PSA