Development of radioimmunometric assay for the determination of free and total prostate-specific antigen in human serum

In the present study, we describe sensitive and reliable immunoradiometric assays (IRMA) for the determination of free (f-PSA) and total (complexed as well as free, t-PSA) prostate-specific antigen in human serum. The assays employ matched pairs of anti-PSA monoclonal antibodies (MAb66 and MAb30 or MAb10). The polystyrene tubes are coated with MAb66 (capture antibody) and the detection antibody MAb30 or MAb10 was labeled with 125I. The minimum detectable dose of f-PSA was less than 0.03 ng/mL, and the assay could determine free PSA concentrations of up to 26 ng/mL; in the case of t-PSA, the minimum detectable dose was less than 0.04 ng/mL while the assay could determine total PSA concentrations of up to 112 ng/mL without dilution of the sample. The intra- and inter-assay variations (%CV) for f-PSA were less than 3% and 15% respectively and for t-PSA less than 2% and 9%, respectively. The results obtained using 44 serum samples correlated well with those obtained by commercially available IRMA kits. (author)