Abstract: The invention relates to a biospecific multiparameter assay method based on the use of different categories of microspheres representing different analytes to be assayed, said categories comprising different amounts of an internal fluorescent dye with short decay time, each category of microspheres being coated with a different biospecific reactant. The method comprises pooling the different categories of microspheres together in a suspension, adding the sample containing analytes to be assayed, adding a mixture of labelled biospecific reactants, diluting the suspension to reduce the concentration of labelled reactants not bound to the microspheres, and identifying the category of each microsphere on the basis of the strength of the electrical signal resulting from the short decay time fluorescent dye. According to the invention, the label of the biospecific reactant is either a compound generating or catalysing a chemior bioluminescence, or a phosphorescent compound.

Abstract: In a biospecific multianalyte assay the use of microspheres and fluorescent labels with substantially different fluorescence decay times, is combined. The assay is performed in a suspension of microspheres in the form of a pool of different microsphere categories, where the categories represent different analytes. The microspheres belonging to the respective categories are first coated with a specific reactant, i.e. the microspheres function as a solid support for the reactant and for a biospecific reaction. Fluorescent labels having a short decay time are used to identify the category of each individual microsphere, while fluorescent labels having a long decay time are used to determine the concentration of a particular analyte on the microsphere by means of the biospecific reaction.