Bridging Enzyme-Linked Immunosorbent Assay (ELISA) is commonly used in detection of antibodies directed against therapeutic proteins. Advantages of the bridging ELISA include the capability to detect antibodies regardless of their isotype or the species of origin. However, detection of antibodies can be difficult, if not impossible, in the presence of high levels of the antigen in the sample matrix. This protocol describes a bridging ELISA that uses a covalently coupled high density antigen surface combined with an acid dissociation step to allow for antibody detection in the presence of antigen in human serum.