FPIA (Fluorescence Polarization Immunoassay)

The ADx/AXsym FPIA Assay Systems use a competitive binding immunoassay methodology to allow tracer-labeled antigen and sample to compete for binding sites on the antibody molecules. The components in this competitive binding reaction are the antibody, the sample antigen, and the antigen labeled with fluorescein (tracer-labeled complex). When competitive binding occurs, the more tracer-antigen complex that becomes part of the very large antibody molecule, the less tracer-labeled antigen complex that remains in solution. If a sample contains a low concentration of the antigen, after the competitive binding reaction reaches steady-state, there will be a high concentration of bound tracer in the reaction mixture and polarization will be high. Conversely, there will be a low concentration of bound tracer in the reaction mixture and polarization will be low. Using the polarization values generated for each sample in the assay, concentrations of drugs in unknown samples are calculated using a stored calibration curve and the results are printed in reportable units.