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How does the PSA SemiQuant work?

The SERATEC® PSA SEMIQUANT test is a chromatographic immunoassay (CIA) for the rapid semi-quantitative determination of PSA in body fluids. It contains two monoclonal murine anti-PSA antibodies as active compounds. One of these antibodies is immobilized at the test region on the membrane. The upstream control
region and the region of the internal standard (between control and test region) contain immobilized polyclonal goat anti-mouse antibodies. The amount of antibody at the internal standard is adjusted to a level at which the line produced equates to a concentration of 4 ng PSA/mL. A glass fiber pad downstream of the membrane is used for sample loading and transmission to a second fiber pad with the dried and gold labeled second monoclonal murine anti-PSA antibody. PSA at the sample will bind to the remobilized gold-labeled antibody and form a PSA-gold-labeled-anti- PSA-antibody-complex. Through the capillary effect of the membrane, the reaction mixture including the complex is carried upwards with the fluid. In any case the colored gold labeled anti-PSA-antibody will bind to the anti-mouseantibody at the control region and the region of the internal standard thus developing two red lines (one at the control region ant one at the region of the internal standard). These two lines are independent of the existence of PSA in the sample and indicate only the correct execution of the test.
If the sample contains PSA, the PSA-gold-labeled anti-PSA-antibody complex will bind to the immobilized monoclonal antibody of the test result region that recognizes another epitope on the PSA molecule (sandwich complex). The binding is indicated by the formation of an additional line. Thus a PSA positive sample will show three colored lines in the result window. The line in the middle (internal standard) correlates with an amount of 4 ng/ml PSA. In some cases it might be helpful to estimate the amount of PSA in the sample by comparison of the test result line with the internal standard line.