[Clinical assessment of free serum prostate specific antigen (PSA)]

The prostate specific antigen (PSA) level represents all of the immunoreactive serum PSA, either free or bound to alpha-1-anti-chymotrypsin. Isolated assay of free PSA has demonstrated a higher free PSA/total PSA ratio in cases of benign prostatic hyperplasia (BPH) than in cases of cancer, suggesting the possible use of this ratio in the detection of prostatic cancer when the PSA level is between 4 and 10 ng/mL. We retrospectively assayed free PSA in 64 cases of localized prostate cancer, 90 cases of BPH before transurethral resection and 59 healthy controls. By comparing the mean values of the 3 populations and the ROC curves, we confirmed the superiority of the free PSA/total PSA ratio over total PSA in the detection of prostatic cancer, but these results, established in a retrospectively constituted population, need to be confirmed by prospective epidemiological studies. Nevertheless, in routine urological practice, we propose that free PSA assay be performed in all men with a PSA level between 4 and 10 ng/mL and a normal prostate on digital rectal examination.