Total Prostate Specific Antigen (tPSA) ELISA

The principle of the following enzyme immunoassay test follows a typical two-step capture or ‘sandwich’ type assay. The assay makes use of two highly specific monoclonal antibodies: A monoclonal antibody specific for total PSA is immobilized onto the microplate and another monoclonal antibody specific for a different region of PSA is conjugated to horseradish peroxidase (HRP). Total PSA from the sample and standards are allowed to bind to the plate, washed, and subsequently incubated with the HRP conjugate. After a second washing step, the enzyme substrate is added. The enzymatic reaction is terminated by addition of the stop solution. The absorbance is measured on a microtiter plate reader. The intensity of the color formed by the enzymatic reaction is directly proportional to the concentration of total PSA in the sample. A set of standards is used to plot a standard curve from which the amount of total PSA in patient samples and controls can be directly read.