Molecular forms of serum prostate-specific antigen: the clinical usefulness of percent free PSA to discriminate prostate cancer from BPH.

The development of increasingly specific diagnostic assays has allowed the detection of various forms of prostate-specific antigen (PSA). It has been found that the proportion of free to total PSA (percent free PSA) is significantly lower in men with prostate cancer than in those with other benign diseases. In order to distinguish early, curable prostate cancer from benign prostatic hyperplasia (BPH), percent free PSA measurement is most useful when the total PSA value is 3-10 ng/ml. The measurement of the proportions of these different forms of PSA, i.e., percent free PSA, may constitute an important diagnostic tool, able to differentiate between benign and malignant prostatic disease with increased specificity, reducing false-positive results and, therefore, improve patient prognosis.