Food Allergy Diagnostic Test Response to Previous Oral Challenge Response

Patients usually discover they have food allergies after consuming a given food and experiencing a subsequent allergic reaction. The majority of patients (75%) will then consult a food allergist for formal diagnosis and treatment information.1 With respect to patient quality of life, there is tremendous benefit in having a confirmed diagnosis of food allergy as often patients are unsure of the source of their reaction outside the office. Allergists will conduct Skin Prick Test (SPT) and assess serum specific IgE levels to screen for specific food protein sensitivities. However, a positive response in SPT and specific IgE will confirm only sensitivity, and in more than 70% of cases patients that respond positively to SPT and specific IgE testing will NOT manifest an allergic response to food consumption.2 To address this issue, most food allergists will recommend an oral food challenge in a controlled setting to confirm the allergic response from consuming the suspected foods. The oral food challenge (OFC) consists of consuming escalating levels of the suspect food, (usually mixed in applesauce or controlled baked goods), until either a reaction manifests or until the challenge is complete with no reaction. The food challenge process poses significant risk to the patient. In 5% of cases, the patient experiences a severe allergic response which requires the use of epinephrine.2,3 These responses typically consist of severe reactions in GI or respiratory and arise from challenging patients with higher doses of food allergen then is necessary to prove a mild allergic response. The reason an allergist would give an increased dose that the patient reacts to with severity results from misdiagnosing the mild forms of the reaction during the titrated challenge. It is this shortcoming in diagnosis that could be addressed by identifying high-risk patient populations through conjunctival allergen challenge and through the development of additional objective diagnostic endpoints.

We hypothesize that conjunctival allergen challenge (CAC) may be able to predict which patients are likely to experience an adverse event during a food allergen challenge. The appearance of severe ocular response following CAC (level II on a 0-2 Scale) has been shown to correlate well with a positive food response during escalating food challenge, and represented a better predictor of food allergen than skin test and serum specific IgE combined.4 We hypothesize that the severity of the ocular response to CAC titration, or the appearance of related non-ocular signs and symptoms of systemic response to CAC (itchy palate, wheezing, FEV1 reduction) could correlate with the likelihood of experiencing a severe adverse event during food challenge. In order to mitigate the occurrence of severe adverse events during food challenge, and to determine if the CAC response can serve as a useful tool for informing the clinician of anticipated patient response patterns to oral food allergen challenge, we will perform CAC titration on a population of food allergy patients that previously underwent oral food escalating challenge. Any patterns in CAC response will be compared to historical food allergen reactivity and occurrence of severe adverse responses to evaluate the potential of the CAC as a predictive tool that could add value to the oral food challenge model.