Abstract: Provided are: a coloring cellulose microparticle enabling false positive to be significantly reduced while maintaining a high detection sensitivity; and an immunochromatographic diagnostic kit using the same.

Abstract: Provided are: a coloring cellulose microparticle enabling false positive to be significantly reduced while maintaining a high detection sensitivity; and an immunochromatographic diagnostic kit using the same. The present invention provides: a coloring cellulose microparticle characterized in that an average particle diameter is 60-900 nm, a coloring intensity is 1.0-10.0, and a hydrophilic layer is provided on the surface of microparticle, and a carboxyl group is introduced onto the surface of the microparticle with a spacer therebetween; a structure in which a ligand is covalently bonded to the carboxyl group of said coloring cellulose microparticle; and an immunochromatographic diagnostic kit including said structure.

Abstract: The present invention provides organic colored microparticles used in an immunochromatography diagnostic kit, the microparticles having good background and test result reproducibility and sufficient detection sensitivity. These organic colored microparticles are characterized in that the average particle diameter is 100 to 650 nm; coloration intensity is 1.0 to 10.0; when a total of 100,000 particles are detected within a particle diameter range of 400 to 12000 nm, the percentage of coarse particles having a particle diameter of 700 nm or greater is 5% or less; and the sphericity represented by the major axis (L)/minor axis (D) is 1.0 to 2.5.