[Babcock_Hall]

https://www.slideshare.net/amerali6/immunochromatographic-assays

Good Morning Everyone,

I have been studying various forensic test kits for body fluids, and a number of them from Abacus Diagnostics or Independent Forensics use lateral diffusion immunochromatography.  In a sandwich format the antigen forms a complex with both the soluble, labeled antibody and the antibody immobilized onto a membrane at the test (T) position.  I can see how this could easily work with a protein such as hemoglobin, which is a tetramer of two alpha and two beta subunits.  It is less clear how this assay works with human salivary alpha-amylase, which is a monomer from what I can gather.  In other words I can see how the sandwich forms when there are multiple epitopes, but it is less clear to me what is happening when there might be only one epitope.

[Yggdrasil]

I am not so familiar with the exact immunochromatographic assays you're referencing, but they seem to be similar to ELISAs, which I do have some familiarity with.  In general for "sandwich" assays, the capture and detection antibodies are different and target different epitopes.  It could be possible to use the same antibody for capture and detection if the antibody is polyclonal, since a polyclonal antibody is a mixture of antibodies targeting multiple epitopes anyway.

[Babcock_Hall]

Yes, it makes more sense that each primary antibody would use a different epitope.