Acnegenicity testing in rabbits. An objective quantification method

Abstract

An objective method for the quantification of follicular hyperkeratosis is proposed for the rabbit ear assay of acnegenicity. The area (area%) of hyperkeratinized follicles, covering a stereomicroscopic photo of the epidermis, is proposed for the quantification of the response. The uniformity of two observers´ quantification was evaluated in six tested formulations. The quantification of the response in area% was found to be a suitable and objective alternative to visual scoring on a graded scale. The median relative difference between two observers´ area%-quantification was found to be 26%, and there was no statistically significant difference between the two observers´ quantification (p greater than 0.10). An area% of 2, 7, and 15 is preliminarily suggested to be equivalent to the lower limit for scores 1, 2 and 3 respectively.