What type of analysis method uses a chromogenic substrate to measure antibody levels?

The method that utilizes a chromogenic substrate to measure antibody levels is indeed the indirect ELISA. This technique involves the attachment of an antigen to a solid surface, followed by the addition of a sample containing antibodies. If antibodies specific to the antigen are present, they will bind to it. After washing away unbound antibodies, a secondary antibody that recognizes the human antibodies is added. This secondary antibody is usually conjugated to an enzyme. The addition of a chromogenic substrate specific to that enzyme leads to a color change; the intensity of the color change correlates directly with the amount of antibody present in the sample.

In contrast, while competitive ELISA also measures antibodies, it operates on a different principle where free antibodies compete with labeled antibodies for binding to the antigen. This type of assay does not primarily rely on color development from a chromogenic substrate.

The Western blot method, although a powerful tool for protein verification, does not use chromogenic substrates for measuring antibody levels; instead, it detects proteins based on size and presence using labeled antibodies.

Immunofluorescence is another distinct method, using fluorescently tagged antibodies to visualize the binding under a fluorescence microscope, rather than measuring levels through a chromogenic change.

Therefore, the use of a chrom