Patent ID: 8287817

Claim:
A downward or vertical flow through test device for determining the presence or absence of a target analyte in a fluid test sample, the test device comprising: a test unit comprising: a reaction zone containing an immobilized capture reagent that binds a target analyte in the fluid test sample to form a two-membered complex of a specific binding interaction, and an absorbent zone in vertical communication with the reaction zone, the absorbent zone comprising an absorbent material positioned underneath the reaction zone for facilitating the downward or vertical flow of the fluid test sample through the reaction zone and into the absorbent zone; and a post-filter cap which is operably affixable to a test unit so as to be in vertical communication with a reaction zone after a fluid test sample has been applied to the reaction zone, the post-filter cap comprising: an outer sleeve comprising an outwardly extending flange, sidewalls depending from the outwardly extending flange and terminating at an open-ended base, the base further comprising a collar projecting inwardly from the sidewalls; an inner sleeve dimensioned to frictionally engage the inner surface of the outer sleeve, the inner sleeve comprising an outwardly extending flange, sidewalls depending from the outwardly extending flange and terminating at an open-ended base; and a removable post-filter unit supported by the collar of the outer sleeve and held in place by the open-ended base of the inner sleeve, the post-filter unit comprising a porous material having a direct label conjugated general marker protein complex embedded thereon, whereby application of a buffer to the porous material mobilizes the direct label conjugated general marker protein complex and liberates the complex from the porous material to flow-through the base of the outer sleeve.