ELISA for a complexed antigen with a monoclonal antibody blocking reactionwith the free antigen - assay-specific for complexed prostate-specific antigen

We have developed an enzyme-linked immunoassay (ELISA) for serum complexed- antigen (prostate-specific antigen; PSA)(c-PSA) with simultaneous blocking of free-antigen (PSA)(f-PSA). The assay utilizes three different monoclonal antibodies (MAbs) recognising three distinct PSA epitopes. The detection l imit was established as 0.19 mu g/l (n = 20, mean of zero standard + 2S.D.) and the average recovery of f-PSA was 98-100%. The within-run and between- day coefficients of variation (CV) ranged from 2.1% to 3.2% and 2.8% to 6.3 %, respectively. There was a good correlation between serum c-PSA measured by the present ELISA and PSA-alpha(1)-antichymotrypsin complex (PSA-ACT) co ncentrations (r = 0.991). This method should provide a better tool for disc riminating between benign and malignant prostatic disease. (C) 2000 Elsevie r Science B.V. All rights reserved.