Label-free epitope binning assays of monoclonal antibodies enable the identification of antigen heterogeneity

► We provide guidelines on how to perform epitope binning on label-free biosensors. ► A heterogeneous antigen may lead to contradictory binning results. ► We describe a diagnostic assay procedure for identifying antigen heterogeneity. ► We recommend a premix format followed by alternative binning formats. ► We corroborate binning data with assays that employ native antigen.