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Holly Irene Lorentz, Victoria Nelson, Nerizsa Tenorio, Anne Marie Salapatek; Retrospective Analysis of Increment Instillation of Allergen During the Conjunctival Allergen Provocation Test (CAPT). Invest. Ophthalmol. Vis. Sci. 2017;58(8):5751.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the differences in ocular response during the allergen concentration dose finding phase of the conjunctival allergen provocation test (CAPT) in birch, ragweed and grass allergic conjunctivitis subjects.
After obtaining informed consent, 169 SPT and allergy positive subjects were screened for their ocular allergic response by performing the allergen concentration dose finding phase (titrating phase) of the CAPT model. Titrating CAPT (tCAPT) involved instilling increasing concentrations of standardized allergen extracts into both eyes until a Positive Ocular Allergic Response (POAR) occurred or until the maximum dose was reached. Subjects reported symptoms of ocular itching and tearing using an electronic Patient Diary Acquisition Tablet (ePDAT™), while staff assessed signs of conjunctival redness. A POAR is elicited when a score ≥ 2 for ocular itching and a score > 2 for ocular redness (in at least one region for both eyes) is established at any time point.
151 subjects responded with a POAR during tCAPT, at varying, subject-dependent allergen concentrations. Overall, as the concentration of allergen increased, subjective and objective scores also increased. Subjects who reached the POAR with lower concentrations of allergen were found to have greater mean change in their symptom and sign scores between concentrations for ocular itching, tearing and redness compared to those who reach their POAR at higher allergen concentrations, at matched timepoints (p<0.05). For example, the 10 min timepoint, those who reached a POAR at the second lowest allergen concentration (125 PNU/mL) had a max mean change between the lowest two CAPT concentrations for itching, tearing, and redness of 1.28±0.16, 0.79±0.12, and 1.67±0.25 respectively, whereas those who reached a POAR at the highest allergen concentration (4000 PNU/mL) had a max mean change of 0.36±0.35, 0.06±0.10, 0.36±0.21 respectively, p<0.05.
In this study, the CAPT model was able to show differences in ocular signs and symptoms between POAR at low and high allergen concentrations, possibly indicating that those who respond to lower concentrations may be more symptomatic or have a more severe allergic responses. This approach could be used to screen for allergy severity in trials.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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