This document is the second edition of the Performance Standards (PS) for the assessment of proposed similar or modified methods to the Direct Peptide Reactivity Assay (DPRA) and the Amino acid Derivative Reactivity Assay (ADRA), both included in TG 442C for in chemico skin sensitisation assays addressing the Adverse Outcome Pathway Key Event on covalent binding to proteins. They are intended for the developers of new or modified similar test methods.