Molecular forms of serum prostate-specific antigen - The clinical value of percent free prostate-specific antigen

It is well established that prostate-specific antigen (PSA) exists in the seminal fluid and serum in several different forms. Patients with prostate cancer have more of the form, in which PSA is bound to alpha-1-antichymotrypsin, and men without benign prostatic hyperplasia (BPH) have more of the free form. As a result, it is suggested that determining the percent free PSA value might be useful in distinguishing men with early, curable prostate cancer from men with BPH only. Percent free PSA is likely to have its greatest clinical impact when the total PSA value ranges from 2.5 to 3.0 ng/mL at the low end to 10.0 ng/mL at the high end.