Well, Sandwich eli is very similar because it still uses this enzyme link molecule that we produce in a laboratory setting. But in the case of sandwich Eliza, we test for a specific type of antigen and not for a specific type of antibody. So sandwich Eliza is generally used to detect the presence of an antigen rather than an antibody, as we saw in indirect Eliza. So let's take a look at the following four diagrams. So in diagram A of indirect Eliza, we coat the surface of the well with an antigen. But in this particular case, we coat the surface with the antibody that can bind to that specific antigen that we are testing for.