Figure 1. Total PSA ELISA comparisons of free PSA CS.

Average absorbance values are plotted against the commercially reported mass concentrations for three free PSA CS (Calbiochem, Scripps, and Fitzgerald) in the (a) Calbiotech and (b) R&D t-PSA immunoassays. One standard deviation is shown for each plotted test point. In both immunoassays, all of the PSA standards had different absorbance values.