What the heck is PSA?


PSA stands for Prostate-specific antigen. PSA is a substance made by cells in the prostate gland (both normal cells and cancer cells). PSA is mostly found in semen, but a small amount is also found in the blood. PSA has also been found in some breast tissue in women, although these amounts of PSA are very low.

What is a PSA blood test?

The purpose of the PSA test is to identify that the prostate gland is stressed and may have significant disease. It is important to understand that the PSA test is not perfect. Most men with elevated PSA levels have noncancerous prostate enlargement, which is a normal part of aging. Conversely, low levels of PSA in the bloodstream do not rule out the possibility of prostate cancer. However, most cases of early prostate cancer are found by a PSA blood test.

If the PSA level is high for your age or is steadily increasing a prostate biopsy may be recommended. The health care provider should consider other health risk factors of prostate cancer such as family history, prostate volume, the presence of benign prostatic hyperplasia (BPH), urinary symptoms, rectal exam findings, ethnicity, and medications that you are taking before recommending the biopsy. At this time, prostate biopsy for pathology review is the only way to determine if prostate cancer or other abnormal cells are present in the prostate.

When should I take the test?

The American Cancer Society says men should talk to their doctors about the benefits, risks, and limitations of prostate cancer screening before deciding whether to be tested. The group’s guidelines make it clear that PSA blood testing should not occur unless this discussion happens. They recommend that most men at average risk for prostate cancer start the discussion at age 50 and those with higher risk for prostate cancer should start the discussion earlier. The American Urological Association recommends that men ages 55 to 69 who are considering screening should talk with their doctors about the risks and benefits of testing and proceed based on their personal values and preferences. The group also adds:

  • PSA screening in men under age 40 is not recommended.
  • Routine screening in men between ages 40 and 54 at average risk is not recommended.
  • To reduce the harms of screening, a routine screening interval of two years or more is recommended over annual screening. As compared to annual screening, it is expected that screening intervals of two years preserve the majority of the benefits and reduce over diagnosis and false positives.

If your doctor is concerned that you might have prostate cancer based on either a PSA level or a rectal exam, a biopsy will be the next step. This is the only way to positively identify the presence of cancer.

Causes of elevated PSA levels:

It is believed that elevation of PSA in the blood is due to its release into the bloodstream because of a disruption of the prostate cellular architecture. 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 growth of prostate glandular cells), prostatitis (inflammation or infection of the prostate), and urinary tract 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 Foley 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. Some physicians may recommend repeating a PSA test to ensure that the elevation is not related to these noncancerous causes.

Just as important as the PSA number is the trend of that number (whether it is going up, how quickly, and over what period of time).

Ways to decrease PSA levels:

Medications commonly taken to treat benign enlargement of the prostate (BPH) such as finasteride (Proscar), dutasteride (Avodart), and a combination of dutasteride and tamsulosin (Jalyn) can decrease the PSA by about 50% within six to 12 months of starting their use. Another medication used to treat fungal infections, ketoconazole, can also lower PSA levels. Lastly, herbal supplements such as saw palmetto and those containing phytoestrogens, which are plant-derived chemicals with estrogen-like effects, can also lower the PSA level. It is important to tell your health care provider all the medications, both prescription and nonprescription, as well as any herbal preparations or health supplements that you are taking.
What are normal ranges for the PSA test?
The “normal” PSA serum concentration remains a debate, however, for most laboratory readings, it should be less than 4.0 ng/mL. The prostate gland generally increases in size and produces more PSA with increasing age, so it is normal to have lower levels in young men and higher levels in older men. Due to these normal changes in PSA with age, the concept of age-adjusted PSA normals have been described and recommended. What is considered to be a normal PSA level also depends on ethnicity and family history of prostate cancer. Once an initial PSA has been obtained, the change in the PSA over time, the PSA velocity, plays a role in clinical decision making. It is felt that the PSA velocity over a year should be less than 0.75 ng/mL. For example, a man 50 to 59 years of age with a PSA level that is 0.5 ng/mL one year and increases to 2.5 ng/mL the following year, may be viewed as having a normal PSA level, but the rate of change in his PSA (PSA velocity) would be worrisome for an underlying prostate cancer. Lastly, as the size of the prostate gland may affect the PSA level, PSA density (PSA level divided by prostate volume) can also be a helpful number. A PSA density of 0.18 or less appears to be an optimal number.

What are age-specific reference ranges for serum PSA?

The use of age-specific PSA ranges for the detection of prostate cancer is helpful to avoid unnecessary investigations in older men with larger prostate glands. Median PSA value for men aged 40 to 49 years is 0.7 ng/mL and for men 50 to 59 years is 0.9 ng/mL. Not all studies have agreed that this is better than simply using a level of 4.0 ng/mL as the highest normal value.

Nevertheless, due to the age-related growth of the prostate, the concept of adjusting the cutoff values based on age has helped reduce unnecessary prostate biopsies in older men to improve early prostate cancer detection. Below are the suggested age-adjusted values based on age and race.

Prostate specific antigen age specific ranges

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