An integrated testing strategy is a type of defined approach to testing and assessment that relies on:
An adverse outcome pathway (AOP) can provide a framework for the development of an integrated testing strategy or a defined approach to testing and assessment. An AOP is a conceptual model that links an exposure to a substance to a toxic effect by identifying the sequence of biochemical events required to produce that toxic effect. In vitro methods that observe or measure the individual events within an AOP can be used as elements of an integrated testing strategy to generate a prediction of whether a chemical might produce that toxic effect.
Substances with the potential to cause allergic contact dermatitis are known as skin sensitizers, and skin sensitization is the process by which a sensitizer induces allergic contact dermatitis. The key biological events of skin sensitization initiated through covalent binding to skin proteins are well characterized and form the basis for an AOP for skin sensitization. NICEATM, working with NTP, ICCVAM, and industry scientists, is creating integrated testing strategies to identify potential skin sensitizers based on this AOP.
The evaluation and promotion of alternative approaches to replace, reduce, or refine animal use for potential skin sensitizer identification is an ICCVAM priority. ICCVAM scientists, in collaboration with NICEATM, developed integrated testing strategies that use non-animal data to predict skin sensitization hazard. These integrated testing strategies combine inputs from several sources (data from the direct peptide reactivity assay, the KeratinoSens assay, and the human cell line activation test; a read-across prediction of skin sensitization hazard generated by the QSAR Toolbox software package; and physical property data such as partition coefficients) to predict skin sensitization hazard and potency.
ICCVAM developed three versions of the skin sensitization integrated testing strategy:
NICEATM and other NTP scientists collaborated with scientists at Procter & Gamble (P&G) to develop an integrated testing strategy to identify potential skin sensitizers without conducting animal tests. Using data from non-animal tests and other information such as solubility and computational predictions of skin sensitizer activity, the strategy produces a numerical probability that a chemical should be placed in a particular skin sensitization hazard class: strong, moderate, weak, or nonsensitizer. This probability could potentially be used to determine if a substance requires hazard labeling without conducting animal tests.
P&G and NTP scientists collaborated to develop this integrated testing strategy using free, publicly available software. The goal is to encourage organizations worldwide to use this approach for identifying potential skin sensitizers and support the elimination of animal testing in this area.
Reference: Pirone et al. 2014. Open source software implementation of an integrated testing strategy for skin sensitization potency based on a Bayesian network. ALTEX 31:336-340.
P&G updated the integrated testing strategy in 2015. The updated strategy uses only validated non-animal tests, simplifies the bioavailability inputs, and nearly doubles the size of the database used to derive the previous network. The updated P&G integrated strategy is the basis for a free web tool produced by Douglas Connect that can be used to predict skin sensitization potency of a chemical.
Reference: Jaworska et al. 2015. Bayesian integrated testing strategy (ITS) for skin sensitization potency assessment: a decision support system for quantitative weight of evidence and adaptive testing strategy. Arch Toxicol 89: 2355-2383.
Files to run the analysis described in Pirone et al., including a script that uses the R programming language, are available below. To encourage collaboration and sharing of best practices, NICEATM has established a user community for the integrated test strategy via an NIH listserv. We strongly encourage all users of the R script to join the listserv.
A bioavailability calculator is available from the National Institute for Occupational Safety and Health (NIOSH) website
Please note that Java must be enabled in your web browser in order to run the calculator.
The software for running R can be obtained from the R Project website
Refer to the FAQs on the R Project website for system requirements and installation instructions.
The OECD QSAR Toolbox can be obtained from the OECD website
Installation instructions and user documentation are available on this page.
On behalf of ICCVAM, NICEATM conducted a number of analyses to evaluate the usefulness of the LLNA to identify potential skin sensitizers. Data from these analyses are available to interested stakeholders as a reference for developing and evaluating alternative approaches to testing and assessment that replace, reduce, or refine the use of animals for identification of potential skin sensitizers.
Database users please note: