Free PSA Prostate Test - Free Prostate-Specific Antigen (Free PSA) Test

This laboratory test measures the concentration of the free (unbound) form of prostate-specific antigen (PSA) in blood serum. PSA is primarily produced in the prostate gland and exists in the blood in two forms: complexed PSA (bound to proteins) and free PSA (free PSA). Measuring free PSA is mainly used to calculate the free PSA/total PSA ratio, a helpful tool when total PSA is elevated to assess the risk of prostate cancer, as a lower ratio tends to be associated with a higher likelihood of developing the disease.