1. A test device for determining the presence or absence of an analyte in a fluid sample, the test device comprising: a) a support bearing a mark thereon; b) a matrix defining an axial flow path affixed to the support, the matrix comprising: i) a sample receiving zone, at an upstream end of the flow path, that receives the fluid sample, ii) a label zone, on the flow path downstream from the sample receiving zone, comprising a label reagent that binds with the analyte in the fluid sample flowing through the label zone, and iii) an observation area, on the flow path downstream from the label zone, the observation area comprising a defined capture zone having an immobilized capture reagent that restrains the labeled analyte, wherein the observation area comprises a material that is opaque in a dry state and transparent in a moist state; wherein the mark on the support is detectable through the observation area when the observation area is in a moist state, wherein upon restraint of labeled analyte, if present, in the capture zone, the capture zone becomes detectable through the observation area, and wherein both the detectable mark and the detectable capture zone are separately distinguishable.