Free PSA test, also known as the free-to-total PSA ratio, is a blood test used to evaluate a man's risk of having prostate cancer. It measures the percentage of unbound PSA, or free PSA, in the blood compared to the total amount of PSA.
PSA is a protein produced by the prostate gland, and elevated levels of PSA can be an indicator of prostate cancer or other prostate conditions. However, not all elevated PSA levels are indicative of prostate cancer, as certain benign conditions such as prostate enlargement or inflammation can also cause PSA levels to rise.