Me-too validation study for in vitro eye irritation test with 3D-reconstructed human cornea epithelium, MCTT HCE^TM

The need for in vitro eye irritation test replacing in vivo is steadily increasing. The MCTT HCE™ eye irritation test (EIT) using 3D reconstructed human cornea-like epithelium, was developed to identify ocular irritants from non-irritants those that are not requiring classification and labelling for eye irritation. Here, we report the results of me-too validation study, which was conducted to evaluate the reliability and relevance of the MCTT HCE^TM EIT, according to performance standards (PS) of OECD TG 492. The optimal cutoff to determine irritation in the prediction model was preliminarily established at 45% with the receiver operation characteristics (ROC) curve for 141 reference substances. To demonstrate the reproducibility of within- and between-laboratory (WLR and BLR), a set of 30 PS reference chemicals were tested in three laboratories three times. The WLR and BLR concordance with the binary decision of whether non-irritant or irritant was estimated to be 90-100% and 90%, respectively, and both met the PS requirements. The predictive capacity of the respective laboratories for the 30 reference chemicals were evaluated based on three different estimation methods, and the results were comparable, with sensitivity ranging from 89.6 to 93.3%, the specificity ranging from 62.2 to 66.7%, and the accuracy ranging from 75.9 to 80.0%. Additional test with the new set of 30 PS substances in the revised OECD GD 216 yielded a performance of sensitivity ranging from 92.6-93.3%, the specificity 62.2-66.7% and the accuracy 77.4-80.0%. 95.0% sensitivity, 67.2% specificity, and 83.0% accuracy were obtained for 141 reference substances in total. Furthermore, separate cutoffs for liquids and solids, 35% and 60%, respectively, produced better predictivity, which was established as a final prediction model. Collectively, our study demonstrated that MCTT HCE^TM EIT meets the reproducibility and predictivity criteria stated in OECD TG 492 PS.