Patent ID: 7270995

Claim:
An analytical device for assaying an analyte in a liquid sample, comprising: a test piece made of a porous material and having a first specific binding substance immobilized at a detection site stably even in the wet state, said test piece having an upper surface, a bottom surface and two side surfaces; a first porous member retaining a second labeled specific binding substance which is mobile in the wet state, the first porous member being in fluid communication with the test piece, wherein the second labeled specific binding substance is positioned apart from the detection site such that an analyte in a liquid sample introduced into the test piece reacts with the first specific binding substance before reacting with the second labeled specific binding substance; a second porous member to which a liquid reagent may be added, the second porous member being in fluid communication with the first porous member such that when the liquid reagent is applied to the second porous member the liquid reagent flows into the first porous member, solubilizes the second labeled specific binding substance, then flows into the detection site by capillary action; and a third porous member to which the liquid sample is added, the third porous member being adjacent to at least one of the sides of the test piece and in fluid communication with the test piece and the detection site such that when the liquid sample is applied to the third porous member, the liquid sample flows into the test piece by capillary action and wets the detection site; wherein the second porous member, the first porous member and the detection site are positioned in this order from upstream to downstream with regard to the flow of the liquid reagent; and wherein the third porous member is not in direct contact with the first porous member.