Clinical evaluation of free PSA/total PSA (prostate-specific antigen) ratio in the diagnosis of prostate cancer.

The objective of this study was to evaluate the utility of the free/total prostate-specific antigen (PSA) ratio (per cent free PSA) in the diagnosis of prostate cancer. Serum total PSA and free PSA concentrations were measured in 156 patients with benign prostate hyperplasia (BPH) and 74 patients with prostate cancer using Hybritech Tandem immunoradiometric assays. Patients with prostate cancer had a significantly lower free/total PSA ratio than patients with BPH, although the distributions across study groups overlapped. In patients with a total PSA level between 4 micrograms/l and 25 micrograms/l, free/total PSA demonstrated better diagnostic utility than total PSA alone.