ADVANTAGES OF REPLACING THE TOTAL PSA ASSAY WITH THE ASSAY FOR PSA-ALPHA-1-ANTICHYMOTRYPSIN COMPLEX FOR THE SCREENING AND MANAGEMENT OF PROSTATE-CANCER

Several advantages become immediately apparent when the prostate speci fic antigen (PSA, or tPSA) assay is replaced by the assay specific for the serum PSA-alpha 1-antichymotrypsin (PSA-ACT) complex. For instanc e, random contributions to the tPSA value by various serum minor PSA i soforms can be avoided, making possible the determination of a more ac curate relation of the PSA-ACT concentration to the tumor activity. Di screpancies in percent free PSA (% fPSA) values from the same specimen s due to the use of different commercial kits also can be eliminated, mainly because the PSA-ACT assay does not have the problems in antibod y selection and calibrator preparation usually associated with the tPS A assay. We found that at the present time different cutoffs of % fPSA for the differentiation of BPH from prostate cancer must be establish ed for each individual tPSA assay. Cutoffs established using values fr om one tPSA assay should not be used for making clinical decisions whe n their tPSA values are determined by a different kit. Moreover, when we monitored the patients during treatment with serum tPSA, specific f PSA, and specific PSA-ACT complex assays simultaneously, it was clear that any interpretation of the patient's clinical status based on tPSA values alone could be misleading. Because there is less PSA-ACT compl ex in BPH specimens relative to that found in cancer serum samples, ex pressing fPSA as ''fPSA/ PSA-ACT x 100'' and measuring PSA-ACT complex concentrations instead of tPSA during screening improve the measurabl e contrast between BPH and prostate cancer. Although individually mode st, collectively these advantages can add up to considerable improveme nts. (C) 1998 Wiley-Liss, Inc.