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.
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