Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (4) Haemoglobin denaturation test

Interlaboratory validation of the haemoglobin denaturation (HD) test on 38 cosmetic ingredients was conducted by five to eight participating laborator ies. The HD test was evaluated as an alternative method to the Draize eye i rritation test (Draize test) based on three indices of protein denaturation : the test substance concentration that induces 50% HD of the positive cont rol (RDC50), a relative HD rate at 1% of the test substance (1%RDR) and a r elative change in maximum absorption wavelength (1% lambda max). The coeffi cients of variation associated with a positive HD lest among the participat ing laboratories were within an acceptable range for practical application. The in vitro test results were in relatively good agreement with the Draiz e test. The correlation coefficient (r) between the ii? vivo maximal averag e Draize total score (MAS) and log (RDC50), 1%RDR and 1% lambda max were -0 .91, 0.67 and 0.79, respectively. The results revealed several limitations associated with the HD test: (1) the HD test cannot be applied to coloured test substances with a strong absorption, around 418 nm; (2) water-insolubl e lest substances cannot be evaluated by RDC50 Or 1%RDR; (3) the HD test ca nnot be applied to strong acids that exceed the buffering capacity of a pho sphate buffer solution; (4) the HD test cannot be used to determine the pot ential for eye irritation caused by factors other than protein denaturation , for example, polyoxyethylene octylphenylether (10 E.O.). Thus, the HD tes t alone is not appropriate for predicting eye irritation potential. Neverth eless, the good agreement between the HD rest results and in vivo irritatio n scores as well as the ease of application suggest that this test may play an important role in a test system to determine eye irritation potential. (C) 1999 Elsevier Science Ltd. All rights reserved.