Evaluation of a modified HET-CAM assay as a screening test for eye irritancy

The hen's egg test-chorioallantoic membrane (HET-CAM) assay, an alternative to the Draize eye irritation test, was developed by Luepke and has been improved on by means of a microscopic examination and the use of a test substance applicator (TSA). The TSA is a double teflon ring in which a perlon mesh is locked, and has several advantages over conventional protocols, reducing subjectivity of the method and avoiding the need for rinsing after treatment. It was confirmed by statistical analysis that the HET-CAM-TSA method can reproduce potentialin vivo irritant effects on the conjunctiva. The classification based on thein vitro results was compared with fourin vivo classifications [MAS (maximal average score) with thresholds of 15.0 and 25.0; the Kay and Calandra method; and EC criteria]. Cooper's parameters (specificity, sensitivity and concordance with the Draize test) were calculated according to these fourin vivo classifications. When the most rigorous classification (MAS threshold of 15.0) was taken into account, a sensitivity of 80%, a specificity of 81.3% and a concordance with the Draize test of 80.4% were obtained for this set of 46 compounds.