Patent ID: 7226793

Claim:
A test device for determining the presence or absence of an analyte in a fluid sample, the test device comprising: a) a housing comprising a support and optionally a cover, wherein the housing contains an application aperture and one or more observation ports, and wherein the support bears a mark thereon; b) one or more matrices comprising an axial flow path and positioned over the support, the matrix comprising: i) a sample receiving zone, at an upstream end of the flow path, that receives the fluid sample through the application aperture, ii) a label zone, within the flow path and downstream from the sample receiving zone, comprising a labeled reagent that binds said analyte, when the fluid sample flows through the label zone to form a labeled analyte, and iii) an observation area comprising a capture zone capable of restraining the labeled analyte, wherein the observation area comprises a material that is opaque in a dry state and transparent in a moist state; and wherein the mark is detectable within the observation area when the observation area is in a moist state.