Prostate Specific Antigen (PSA) is a protein made by the prostate, a small gland in men that creates fluid for sperm. Most PSA in the blood is bound to serum proteins.
The % free PSA refers to the amount of PSA in your blood that is not connected to other proteins. This percentage is used to help differentiate between benign prostate conditions and prostate cancer, especially when total PSA levels are in the borderline range (4–10 ng/mL). In men over 50 years with total PSA in this borderline range, the measurement of the % free PSA may aid in avoiding unnecessary biopsies.
Abnormal % Free PSA
Low % Free PSA - Cause
Low levels are often associated with a higher risk of prostate cancer. When total PSA levels are elevated, a lower percentage of free PSA (less than 25%) might indicate a greater likelihood of cancer.
Low % Free PSA - Symptoms
Low % free PSA may not cause specific symptoms directly but could indicate the presence of prostate cancer, which might present with urinary symptoms, such as:
- Difficulty urinating or frequent urination (especially at night)
- Weak urine stream
- Blood in the urine or semen
High % Free PSA - Causes
A high % free PSA generally indicates a lower risk of prostate cancer and is often associated with benign prostatic hyperplasia (BPH) or prostatitis.
High % Free PSA - Symptoms
High levels of % free PSA do not directly cause symptoms. However, if the elevated levels are due to an underlying prostate condition (BPH or prostatitis), which can cause urinary symptoms such as:
- Frequent urination
- Difficulty starting and stopping urination
- Weak or interrupted urine stream
- Pain or discomfort during urination
- A feeling of incomplete bladder emptying
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