Analysis of a serum test for prostate cancer that detects a second epitope of EPCA-2

BACKGROUND. We have previously shown that EPCA-2 can serve as a highly specific and sensitive serum marker for prostate cancer. As a component of our validation of this marker, we have performed an initial evaluation of an assay that detects a distinct epitope of the same protein: EPCA-2.19. The goals of this study are to characterize the sensitivity and specificity of the EPCA-2.19 assay, in a non-screening population, and to demonstrate that such test based has similar characteristics as the initial assay produced. METHODS. Three hundred twenty-eight serum samples from men with PSA values < and >2.5 ng/ml who had negative biopsies, men with BPH, men with organ-confined and non-organ-confined prostate cancer, as well as control populations were evaluated using the EPCA-2.19 assay. RESULTS. At a cut-off of 0.5 ng/ml and above, EPCA-2.19 has a specificity of 94% and a sensitivity of 91% in separating normal men with PSA < and >2.5 ng/ml, and men with BPH from those with prostate cancer. Receiver Operator Curve analyses of the EPCA-2.19 assay demonstrate an area under the curve of 0.982 (95% CI 0.952-0.996, P<0.0001). CONCLUSIONS. This study confirms our earlier findings that the assay that detects against a second epitope of EPCA-2 yields almost identical results to those obtained for the first published assay (EPCA-2.22). While this provides some validation of our earlier studies, larger multi-institutional studies still need to be performed.