Development of Simultaneous Detection of Total Prostate-Specific Antigen (tPSA) and Free PSA With Rapid Bead-Based Immunoassay

Objective: Prostate-specific antigen (PSA) is the most important biochemical tumor marker for the early detection of prostate cancer; however, its diagnostic specificity is low. Therefore, free PSA (fPSA) test is recommended as an adjunct to increase the specificity. However, all the current technology only allows detecting one biomarker at one time. In this study, we reported a flexible bead-based immunoassay to measure total PSA (tPSA) and fPSA simultaneously. Materials and Methods: We used the Luminex xMAP bead array technology to measure tPSA and fPSA at one time, employing two mouse monoclonal anti-PSA antibodies (5G6 and 8A6) for coating and another mouse monoclonal anti-PSA antibody (5A6) for detection. Then we compared the data of Luminex assay with that of the conventional enzyme-linked immunosorbent assay (ELISA). Results The assay was fast with a wide dynamic range. The lower detection limit for tPSA and fPSA were 2.3 and 1.3 pg/ml. The inter-assay coefficients for tPSA and fPSA were between 5.64 and 7.65%, and the intra-assay coefficients for tPSA and fPSA were between 4.15 and 5.89%. A close correlation between the new assay and the conventional ELISA was observed. Conclusions The bead-based platform is rapid, sensitive, and less expensive, which allows both single sample and high-throughput measurement of tPSA and fPSA over a wide range of concentrations. J. Clin. Lab. Anal. 25:37-42, 2011. (C) 2011 Wiley-Liss, Inc.