For Research Use Only. Not for Use in Diagnostic Procedures. Bio-immuno assay for the measurement of PAI-1 activity. Assay designed with an ELISA plate coated with active tPA, then stabilized, which binds active PAI-1 present in plasma or in tested sample. This is then revealed with a specific Murine monoclonal antibody, specific for PAI-1, and labeled with Horse Radish Peroxidase (HRP).