Electrophilic Allergen Screening Assay (EASA)
DOI for Publication: https://doi.org/10.22427/NICEATM-3
DOI for CEBS Data Page: https://doi.org/10.22427/NICEATM-DATA-NICEATM-3
This NICEATM report summarizes the key findings of a validation study for the EASA conducted by four laboratories, representing a collaboration among five ICCVAM member agencies. The study assessed the EASA’s within- and between-laboratory reproducibility and its performance against in vivo reference data. The report also discusses the purpose and scientific rationale of the EASA, describes the conduct of the assay and problems encountered during the validation process, and addresses the EASA’s predictive capacity and applicability domain. The information from this study may support future consideration of the EASA for addition to existing accepted test guidelines for similar methods, and whether the EASA could be used as part of an integrated approach for testing and assessment and/or a defined approach to discriminate between skin sensitizers and nonsensitizers for hazard classification and labeling and potency categorization.
Binding of a chemical to skin proteins is the first step in the development of allergic contact dermatitis. The EASA is a chemical assay that measures light absorbance or a fluorescent signal in proportion to a chemical’s tendency to bind to proteins.
In 2022, a validation study coordinated by NICEATM completed testing of 20 chemicals using the EASA in a 96-well format. Results of this study suggest that the EASA may be a useful non-animal method to identify potential skin sensitizers. The study is summarized in the report linked above.
Background of the ICCVAM Validation
The EASA was nominated to ICCVAM to evaluate its usefulness in identifying potential skin sensitizers. Initial testing of 10 chemicals showed that the method had sufficiently good reproducibility and accuracy rates to support further evaluation. Scientists with ICCVAM member agencies CPSC and NIST subsequently modified the assay to a 96-well format to increase throughput and accessibility of the assay. Petersen et al. (2022) describes this process, including the incorporation of in-process control measurements to quantify key sources of variability each time the assay is run.
- Nomination cover letter for the EASA from Paul Siegel, PhD, National Institute of Occupational Safety and Health.
- NICEATM Preliminary Evaluation of the EASA.