Patent ID: 7326573

Claim:
A method of examining a composition which comprises a plurality of particles, each of the particles (i) having a coding characteristic, (ii) containing analyte-interaction sites and/or corresponding analyte-bearing sites which are the same as said analyte-interaction sites except that they have interacted with one or more analytes and have associated therewith one or more fluorochromic signal dyes, and (iii) belonging to one only of a plurality of defined categories, each of the particles in each defined category (a) having the same coding characteristic, and (b) containing the same analyte-interaction sites and/or corresponding analyte-bearing sites; the combination of the coding characteristic and the analyte-interaction sites and/or corresponding analyte-bearing sites on the particles in each category being different from the combination of the coding characteristic and the analyte-interaction sites and/or corresponding analyte-bearing sites on the particles in other categories; the method comprising examining, one at a time, each particle of a representative sample of the particles, the examination comprising: (A) determining the coding characteristic of the particle, including whether the particle is a single-assay particle or a dual-assay particle; (B) subjecting the particle to radiation from a laser which causes fluorescence of any fluorochromic signal dye associated with analyte-bearing sites on the particle; (C) assessing the fluorescence caused by the laser and falling within a first wavelength band; (D) assessing the fluorescence caused by the laser and falling within a second wavelength band; and (E) when step (A) determines that the particle is a single-assay particle, combining the fluorescence in the first wavelength band and the fluorescence in the second wavelength band, and when step (A) determines that the particle is a dual-assay particle, recording separately the fluorescence in the first wavelength band and the fluorescence in the second wavelength band.