Patent ID: 7179657

Claim:
A test device for determining the presence or absence of an analyte in a fluid sample, the test device comprising: a) a matrix, the matrix comprising: i) a porous first member comprising an observation area comprising a capture zone said capture zone having an immobilized capture reagent that restrains the analyte, wherein the first member comprises a material that is opaque in a dry state and transparent in a moist state; and ii) a porous second member bearing a mark thereon, disposed below and contacting said first member, wherein said second member allows fluid flow through the first member into and through the second member when a fluid sample is introduced; and b) the mark on the second member is detectable through the observation area in the first member when the first member is in the moist state; and c) wherein upon introduction of a separate detectable label reagent that binds with the analyte in the fluid sample, the capture zone becomes detectable in the observation area, and wherein the detectable mark and the detectable capture zone are separately distinguishable.