How does indirect elisa tests work?

Indirect ELISA (Enzyme-Linked Immunosorbent Assay) works by detecting the presence of specific antibodies in a sample. Initially, the antigen of interest is coated onto a microplate. When the sample, which may contain antibodies, is added, any specific antibodies will bind to the antigen. A secondary enzyme-linked antibody specific to the primary antibody is then added, followed by a substrate that the enzyme can convert to a detectable signal, such as a color change, indicating the presence and quantity of the antibodies in the sample.