An in vitro skin corrosivity test--modifications and validation.

An in vitro rat epidermal slice technique has been developed for identifying chemicals with potential to cause a corrosive lesion in animal skin in vivo. This potential has been correlated with the ability to lyse stratum corneum and has been measured as a lowering of the electrical resistance of the skin slice. Initial validation of the technique with 63 chemicals resulted in a high sensitivity for corrosive chemicals but a lower specificity for irritant chemicals. Subsequent modification relating to chemical contact resulted in an improved specificity (i.e. fewer false positives) at the expense of a small loss in sensitivity (i.e. an increase in the number of false negatives). An intralaboratory double blind trial with 34 corrosive chemicals and 36 irritants showed the technique to have total sensitivity (i.e. no false negatives) and a specificity of 88%. The results of the initial validation and the double blind trial illustrate the robust nature and high reproducibility of this in vitro technique for identifying skin-corrosive chemicals. Overall the model has considerable potential as a pre-screen for conventional animal tests with the additional advantage of providing objective and quantifiable information.