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PSA (Prostate-Specific Antigen) Blood Test

What Is It?

The PSA is a protein that is only made by the prostate gland. Any man who has a prostate will have at least a small amount of PSA level in the blood. The PSA blood test is not specific for cancer, so a PSA level that is higher than normal does not always mean that cancer is present. An infection or inflammation of the prostate can raise the PSA level. The prostate can also get larger and that can raise the PSA level.

PSA testing is most helpful after cancer has been diagnosed. It can be used to see how serious the cancer is. Generally, a very high PSA is worse than a slightly high one. However, aggressive cancers may not make much PSA protein, giving a low level as well. The PSA level is also used to see if treatment for cancer has worked. If the PSA level returns to very low levels after treatment, but then begins to rise again, it is likely the cancer has recurred. Men who have had their entire prostrate gland removed should have no detectable PSA level.

What Is Normal?

Any PSA level below 4.0 is normal. However, a normal level depends on a man's age and the size of his prostate. Older men have higher PSA levels than younger men. Men with a larger prostate have higher levels than those with a small prostate. A man can have prostate cancer with any level of PSA. But, the higher the level, the greater the likelihood that cancer is present.

When Is A Biopsy Appropriate?

Your doctor considers many things before advising you to have a prostate biopsy. These include:

  • Your PSA level
  • The change in the level over time
  • The fraction of total PSA in the blood that is not attached to other proteins over total PSA. (This value is a lot lower in men who do have prostate cancer than in men who do not.)
  • Your age
  • Your family history of prostate cancer
  • Other risk factors:
    • race (prostate cancer is more common in African-Americans)
    • results of prior biopsies
    • urinary symptoms

Please share any questions you have about this information with your doctor or nurse.