A reagent kit that is used for determining a characteristic of tissue obtained from a patient is described. The reagent kit comprising expression measurement reagents for measuring expression level of cyclin-dependant kinase (CDK) and activity measurement reagents for measuring activity value of CDK. The expression measurement reagents comprise first reagents and second reagents, and the activity measurement reagents comprise third reagents and fourth reagents. In the reagent kit, a first reagent set of the first and third reagents is stored under a first storage condition relating to temperature, and a second reagent set of the second and fourth reagents is stored under a second storage condition relating to temperature.