Method of storing latex particle dispersion liquid

A method for storing in a container a latex particle dispersion liquid in which latex particles for an extracorporeal diagnostic agent are dispersed, the latex particles having a volume average particle size of 10 to 1000 nm and comprising a polymer comprising 70 to 100% by mass of monomer units each derived from a monomer having an aryl group relative to the total monomer units, the method comprising

• setting a ratio of a volume of a void space obtained by excluding a volume occupied by the latex particle dispersion liquid from an internal volume of the container to 0 to 25% (v/v) relative to the internal volume of the container, and
• putting the latex particle dispersion liquid in the container in an amount to satisfy the ratio and to store the latex particle dispersion liquid in the container,
• wherein the container is provided with a housing that houses the latex particle dispersion liquid and that has a flexibility of being deformed so as to deflate with a decreasing amount of the latex particle dispersion liquid.