Purchase this article with an account.
R. Chaturvedi, P. J. Gomes, D. Welch, M. B. Abelson; A Retrospective Analysis of the Predictive Value of Skin Tests Used in Subjects Screened in the Conjunctival Allergen Challenge Model. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2297.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A retrospective analysis on two conjunctival allergen challenge (CAC) studies was performed to determine the predictive value of skin testing as it applies to ocular allergic sensitivity to the allergen (deleted induced by CAC).
Data was obtained from 306 subjects in two single-center, double-masked, randomized, placebo-controlled, four visit CAC studies. Prior to a titration visit 1, subjects underwent a skin prick test. The skin prick testing used ten different allergen extracts, consisting of tree, ragweed, grass, and cat pollen. The results of the skin tests were measured and recorded. Itching, swelling and/or redness at the site of the allergy extract application indicated a positive reaction to the allergen. Skin test reactions were based on the size of the wheal and flare, graded on a 0 to 4 scale. Subjects with a positive skin test were bilaterally challenged with the most reactive allergen extract in a titrated fashion. Subjects assessed ocular itching and the examiner assessed ocular hyperemia using standardized 0 to 4 scales. A successful CAC was defined as a redness score of ≥ 2 in 2 of 3 vessel beds (ciliary, conjunctival, and episcleral) and a ≥ 2 itching score bilaterally within 10 minutes of the CAC.
Three hundred and six subjects in total were screened for these studies. Subjects with a skin test reaction ≥ 2 had a significantly higher percentage of success (84%) in qualifying for these studies than subjects with a < 2 skin test reaction (57%). Furthermore, there was a negative correlation between the skin test reaction and the qualifying CAC dose. Therefore, a subject with a stronger skin test reaction was more likely to require a lower qualifying allergen concentration.
Skin tests have a high predictive value in subject enrollment success and sensitivity to allergen in CAC trials. Not only are subjects with a stronger skin test reaction to a particular allergen more likely to qualify, but they are more likely to do so at a lower qualifying allergen concentration than those subjects with a lower skin test score.
This PDF is available to Subscribers Only