Development and validation of a quantitative ELISA for the measurement of PSA concentration

Abstract

Background: Prostate-specific antigen (PSA) has been used for the diagnosis and follow up of prostate cancer (PCa). Methods: Mouse monoclonal antibodies (MAbs) were generated against human prostate-specific antigen (PSA) for the development of a sensitive total PSA (t-PSA) assay. Two MAbs, denoted CB-PSA.4 and CB-PSA.9, with affinities of 3.7×10 9 and 4.7×10 10 l/mol, respectively, were used to develop an enzyme-linked immunosorbent assay (ELISA) for quantifying serum t-PSA concentration. Results: The detection limit (DL) of the assay was 0.1 μg/l ( n=20, mean of “zero” standard+3S.D.), and the recovery of t-PSA was 96–103%. The within-run and between-day coefficients of variation (CV) ranged from 2.1% to 3.2%, and from 2.8% to 6.3% for PSA concentrations of 10 and 1 μg/l, respectively. The equimolar detection of t-PSA and free-PSA was demonstrated by two different methods, one consisted in the comparative evaluation of a sera panel ( n=9) with our enzyme-linked immunosorbent assay (ELISA) and four commercial total PSA assays and the concordance with CIS bio total PSA assay. The assay had a linear range of 0.12 to 25 μg/l. Conclusions: The analytical performance characteristics of our PSA ELISA suggest that it will provide clinically useful PSA results, particularly when diagnostic algorithms are used.