Method for adding an apparent non-signal line to a lateral flow assay

A test device for determining the presence or absence of an analyte in a fluid sample, the test device comprising:

• a) a solid support;
• b) an intermediate piece bearing a mark thereon;
• c) a matrix defining an axial flow path, 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 analyte, wherein the observation area comprises a material that is opaque in a dry state and transparent in a moist state and the mark on the intermediate piece is visible through the observation area when the observation area is in the moist state;
• wherein the intermediate piece is disposed between the matrix and the support,
• iv) the mark has a shape such that, in the absence of the analyte in the sample, a first symbol is displayed to represent a negative result, and
• v) the capture zone has a shape such that, in the presence of analyte in the sample and taken together with the first symbol, a second symbol is formed to represent a positive result.