Prostate Cancer Health Center

Prostate-Specific Antigen (PSA) Blood Test

Prostate-specific antigen (PSA) is a substance produced by the prostate gland. Elevated PSA levels may indicate prostate cancer, a noncancerous condition such as prostatitis, or an enlarged prostate.

Most men have PSA levels under four (ng/mL) and this has traditionally been used as the cutoff for concern about the risk of prostate cancer. Men with prostate cancer often have PSA levels higher than four, although cancer is a possibility at any PSA level. According to published reports, men who have a prostate gland that feels normal on examination and a PSA less than four have a 15% chance of having prostate cancer. Those with a PSA between four and 10 have a 25% chance of having prostate cancer and if the PSA is higher than 10, the risk increases to 67%.

In the past, most experts viewed PSA levels less than 4 ng/mL as normal. Due to the findings from more recent studies, some recommend lowering the cutoff levels that determine if a PSA value is normal or elevated. Some researchers encourage using less than 2.5 or 3 ng/mL as a cutoff for normal values, particularly in younger patients. Younger patients tend to have smaller prostates and lower PSA values, so any elevation of the PSA in younger men above 2.5 ng/mL is a cause for concern.

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). 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.

How Is The PSA Screening Test Done?

The test involves drawing blood, usually from the arm. The results are usually sent to a lab and most often come back within several days.

When Should I Have My PSA Levels Tested?

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 prostate-specific antigen (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 U.S. Preventive Services Task Force, however, doesn't recommend routine PSA screening for men in the general population, regardless of age. They say the tests may find cancers that are so slow-growing that medical treatments -- which can have serious side effects -- would offer no benefit.