Abstract: An object of the present invention is to provide an improved detection method for a specimen substance in a sample. The present invention provides a multiphase polymer fine particle having two or more polymer phases formed by aggregation of two or more polymers, respectively, at least on a surface thereof, wherein a first polymer phase can bind to a specimen substance or a substance that can specifically bind to the specimen substance, and a second polymer phase has a labeling substance. By utilizing the fine particle, the specimen substance in the sample having a biological origin or the like can be quickly detected with high sensitivity.

Abstract: An object of the present invention is to provide a sensor that can quickly and easily detect primary aldosteronism with a higher accuracy. The present invention provides a method of quickly detecting aldosterone or renin in a sample with high sensitivity, using a multiphase polymer fine particles having at least on a surface thereof two or more polymer phases formed by aggregation of two or more polymers, respectively, wherein aldosterone or renin covalently binds to a first polymer phase, and wherein a second polymer phase has a labeling substance.