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 or 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 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 laboratory and most often come back within several days.

When Should I Have My PSA Levels Tested?

PSA blood tests and digital rectal exams should be done every year for men beginning at age 50, and earlier (age 40) for African American men and men with a family history of prostate cancer.

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

What does the PSA test tell me about my prostate?

A raised PSA level can be a sign that you have prostate cancer. The PSA level is often raised well before any symptoms of prostate cancer develop. So the test can help to detect early prostate cancers (which may have a better chance of being successfully treated than more advanced prostate cancers.) As a rule, the higher the PSA level, the more likely that you have prostate cancer.

However, a raised PSA level can also occur in other prostate conditions such as some cases of benign enlargement of the prostate and inflammation of the prostate (prostatitis). In particular, a PSA level that is mildly or moderately raised has a good chance of being due to a benign condition, but could be due to prostate cancer. Overall, about 2 in 3 men with a raised PSA level do not have prostate cancer.

Also, if you do have prostate cancer, a single PSA test cannot tell you whether a prostate cancer is slow or fast growing.

And also, in some cases, the PSA level may be normal even when there is cancer there. Up to 1 in 5 men with prostate cancer have a normal PSA level.

So, the PSA test is not an accurate test for prostate cancer.