CLINICAL USEFULNESS OF PERCENTAGE OF FREE SERUM PROSTATE-SPECIFIC ANTIGEN

Serum concentrations of total and free prostate specific antigen were measured retrospectively in 268 patients, in order to test the usefuln ess of percentage of free prostate specific antigen in distinguishing between cancer and benign hyperplasia of the prostate and to improve t he specificity of cancer screening. Four groups were investigated: 94 urologic patients without prostate disease (controls), 98 patients wit h a histologically confirmed benign hyperplasia, 76 with a histologica lly established prostatic adenocarcinoma, 18 of them after radical pro statectomy. Total and free prostate specific antigen concentrations we re measured in frozen serum, in a retrospective mode, by using an equi molar monoclonal antibody immunoassay. Median percentage of free prost ate specific antigen was 20.48% in controls, 17.75% in patients with h yperplasia, 10.52% in patients with cancer and 33.03% in patients afte r prostatectomy. Median percentage of free prostate specific antigen w as significantly lower in men with cancer than in patients with benign hyperplasia (P < 0.0001). The percentage of free prostate specific an tigen increased the specificity of cancer screening: a cut-off of 23.6 % detected at least 90% of cancers and would have eliminated 34.7% of biopsies in benign hyperplasias. A prospective study is ongoing to con firm these results. Copyright (C) 1997 Elsevier Science B.V.