Diagnostic Blood Test: Prostate Specific Antigen (PSA) (Reflex to Free) If PSA is between 4 and 10 ng/mL reflex testing to PSA, Free is performed.Prostate-Specific Antigen (PSA) is a protein produced by the prostate. Elevations of PSA are a marker of prostate cancer or another prostate problem such as prostatitis or benign prostatic hyperplasia (BPH). High PSA levels may indicate the need for re-testing, a prostate exam, or potentially a biopsy.Free PSA is a measure of unbound PSA that is available to the body’s tissues.