Category consistency in the OECD QSAR Toolbox: Assessment and reporting tool to justify read-across

Abstract Read-across is an alternative or supplementary method to the use of test results (including test results from tests employing laboratory animals) for chemical hazard assessment. Its use by both the industrial and the regulatory communities has increased markedly over the past decade. A seminal issue for the regulatory acceptance of read-across predictions is reducing uncertainty in the prediction by evaluating similarity among the chemicals participating in the read-across. To assist in demonstrating and documenting this similarity, a “category consistency” functionality has been added to the OECD QSAR Toolbox. This module (semi-) automatically collects and displays information key to establishing physicochemical, structural and mechanistic similarities, as well as any experimental data associated with the endpoint under consideration. The Toolbox user can then employ this suite of information to draw a conclusion on the consistency of the recorded similarity measurements of the category members. The report writer provides documentation of the Toolbox information supporting the conclusion. The implementation of “category consistency” functionality is illustrated with a case example.