Multi-center analytical performance evaluation of the Access Hybritech® p2PSA immunoassay

Background: Total PSA assays measure both complexed and non-complexed forms of PSA while free PSA assays only measure non-complexed forms. Free PSA is a mixture of isoforms including immature PSA (proPSA) with retained portions of the leader sequence (e.g. [- 7], [- 4], and [- 2]proPSA) and nicked forms (BPSA). ProPSA isoforms in male sera have been associated with prostate cancer. This study characterized the analytical performance of a chemiluminescent immunoassay for [- 2]proPSA. Methods: The Access Hybritech p2PSA assay is a sandwich immunoassay using an anti-[- 2]proPSA monoclonal antibody attached to paramagnetic beads and an anti-PSA monoclonal antibody conjugated to alkaline phosphatase calibrated with recombinant [- 2]proPSA. Analytical studies including sensitivity (CLSI EP17-A) and imprecision (CLSI EP5-A2) were performed. Results: The Access Hybritech p2PSA assay for [- 2]proPSA had a dynamic range of 0.5 to 5000. pg/ml. The total CV of the assay was < 7% for [- 2]proPSA concentrations between 20 and 1000. pg/ml. The LOB was 0.50. pg/ml, LOD 0.69. pg/ml, and LOQ 3.23. pg/ml (20% CV). There was no hook effect up to 15,000. pg/ml. There was a < 5% difference between calibrator and reagent lots and no interference from normal serum constituents. Conclusions: The Access Hybritech p2PSA assay is a robust immunoassay for the measurement of serum [- 2]proPSA.