Patent ID: 7192786

Claim:
In a biospecific assay method comprising reacting microparticles coated with a bioaffinity reactant A which specifically binds at least one analyte to be assayed, a sample to be analyzed, and a labelled bioaffinity reactant B to cause said analyte and said labelled bioaffinity reactant B to specifically bind to said microparticles via the bioaffinity reactant A; and measuring signal strength from labelled bioaffinity reactant B bound to the microparticles to determine the analyte concentration in the sample, the improvement comprising: contacting a predetermined amount of said sample, a predetermined number of uniformly sized microparticles coated with said bioaffinity reactant A and said labelled bioaffinity reactant B labelled with a luminescent label such that, after the specific binding of the analyte in the sample to said predetermined number of uniformly sized microparticles, each individual microparticle emits a signal strength that corresponds to the analyte concentration in the sample, and measuring the signal strength from an individual microparticle using a measuring means capable of reading the luminescence from an individual microparticle, and determining the analyte concentration in the sample by comparing said signal strength measured from said individual microparticle with a standardization curve, wherein said standardization curve is a mean of the signal strength of said predetermined number of uniformly sized microparticles.