Prostate Specific Antigen PSA, is an enzyme found in the blood produced exclusively by prostate cells. Normal levels of PSA in the blood are small amounts between 0-2.5 ng/ml. Higher than normal levels, greater than 2.5 ng/ml, can be caused by cancer or benign, non-cancerous conditions such as enlarged prostate, prostate inflammation, infection, or trauma. All elevated readings of PSA should be checked.
Occasionally, a Digital Rectal Exam (DRE) does not reveal any abnormalities, but the PSA is elevated. Sometimes the opposite is true, and PSA is normal, but the DRE is abnormal. For this reason, the Prostate Specific Antigen PSA blood test together with the DRE is best for early detection.
Reference: Prostate Cancer Free Foundation website
What is FREE PSA?
Total PSA is the sum of the free and the bound forms. Most PSA binds to other proteins in the blood. The remaining unattached PSA is named “free” PSA. Men with a lower percentage of free PSA have a higher risk for prostate cancer. Therefore a high free PSA percentage is good. Free PSA is not used to monitor results after treatment only to evaluate risk before diagnosis. The free PSA test is particularly helpful in situations where a biopsy is negative but the PSA is slightly high. If there is a low free PSA, another biopsy 6-12 months later is usually recommended. If it is high, then a longer wait is usually recommended.