What do the test results mean?

Men who have low free PSA levels may be at risk for developing prostate cancer. These men may benefit from more frequent testing to detect prostate cancer. These tests include rectal examinations or prostate biopsies.

The best way to determine if a man has a low free PSA level is to calculate the percentage of free PSA. This is done by dividing the value reported for free PSA by the value reported for the standard or total, which is free plus bound PSA. If the calculated percentage is greater than 23%, the risk of prostate cancer is minimal. If the percentage is less than 10%, the risk of prostate cancer is high or more likely. If the percentage is between 10% and 23%, the risk of prostate cancer is not clear or not well defined.

The free PSA test has not been approved by the US Food and Drug Administration for predicting the risk of prostate cancer. Many laboratories do not offer this test and many insurance companies do not pay for it. Free PSA values between 4 and 10 are reliable and accurate. Values below 4 and above 10 may not be reliable. More information is needed before this test can be used routinely to screen men for prostate cancer, or to monitor the progress of the disease or its treatment.