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Paul J Gomes, Emily Schoemmell, Sarah Ellen Godek, Endri Angjeli, Keith Jeffrey Lane; Use of Conjunctival Allergen Challenge as a Tool for Predicting Response to Oral Food Challenge in Food Allergic Patients. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5752.
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Current diagnostic tests for assessing food allergies include Skin Prick Tests (SPT) and Oral Food Challenges (OFC). Due to the overwhelming false positives associated with a SPT, many patients are required to undergo an OFC, which poses a significant risk to the patient due to the potential for a severe systemic allergic response. We proposed that the conjunctival allergen challenge (CAC) may be able to predict which patients are likely to experience an adverse event during an OFC. A moderate to severe ocular response following CAC (level 2 on a 0-4 Scale) has been shown to correlate well with a positive food response during an escalating OFC, and might be a better predictor of food allergies than a skin test and serum specific IgE combined.
Seventeen subjects ≥ 5 years of age who exhibited a positive SPT to a food allergen and received an OFC within the prior year were included in the study. The subjects received a CAC in titrated incremental allergen doses in a maximum of 8 steps, starting at a 1:320 dilution. Conjunctival redness, itchy palate, and ocular itch were assessed 10 minutes after each dose. A positive result was defined as ≥ 2 for ocular itch and ≥ 2 for conjunctival redness in both eyes. The food allergens were peanut, milk, egg, shellfish, soy and almond. The primary endpoint was mean allergen dose step at which a positive reaction was observed.
Of the 17 subjects, 5 had a positive OFC and 12 had a negative OFC. Of the 5 subjects who had a positive OFC, all had a positive CAC response at a low allergen dose (mean dose step of 3.3±3.1). Of the 12 subjects who had a negative OFC, 5 had a negative CAC response, and 4 subjects had a positive CAC at a high allergen dose (mean step of 7.0±1.4). The remaining 3 subjects (mean dose step of 4.3±2.1) had a high score in only ocular itching or redness, and therefore challenges were discontinued.
A low-threshold CAC is an effective predictor for a positive response to an OFC. A positive high-threshold CAC and negative OFC might indicate a food sensitivity rather than allergy. The CAC can be used as an effective screening tool for identifying patients who exhibit food allergy without the risks of anaphylaxis associated with an OFC.
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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