Abstract: The invention concerns a method for detecting an analyte in a blood sample or a derived fraction thereof. In this method one uses the binding affinity between the analyte and its specific binding agent. Moreover, a reaction component containing a peroxidase label is added to the sample and specific binding agent to form a reaction mixture. The incubation of the reaction mixture, containing the analyte and its specific binding agent, with the peroxidase-labeled reaction component has to be carried out in the presence of a quaternary ammonium salt or ionic surfactant.

Abstract: Processes, reagents and test kits for the qualitative and/or quantitative determination of an immunochemically reactive component, in which one or more labelled components are used, that are obtained by direct or indirect coupling of such a component or components to particles of an aqueous dispersion of a hydrophobic dye or pigment, or of polymer nuclei coated with such a dye or pigment.During the reaction or after an adequate reaction time the nature and/or the quantity of the dye is determined in the test medium, or optionally after a separation of the bound and free labelled components in one of the fractions.