A consensus protocol for the determination of the threshold doses for allergenic foods: how much is too much?

Abstract

SummaryBackground While the ingestion of small amounts of an offending food can elicit adverse reactions in individuals with IgE-mediated food allergies, little information is known regarding these threshold doses for specific allergenic foods. While low-dose challenge trials have been conducted on an appreciable number of allergic individuals, a variety of different clinical protocols were used making the estimation of the threshold dose very difficult. Objective A roundtable conference was convened to develop a consensus clinical protocol for lowdose challenge trials for the estimation of threshold doses for specific allergenic foods. Methods In May 2002, 20 clinical allergists and other interested parties were invited to participate in a roundtable conference to develop consensus of the key elements of a clinical protocol for lowdose challenge trials. Results A consensus protocol was developed. Patients with convincing histories of food allergies and supporting diagnostic evidence including past challenge trials or high CAP-RAST scores can be enrolled in low-dose challenge trials. Care must be taken with younger patients to assure that they have not outgrown their food allergy. An approach was developed for the medication status of patients entering such trials. Challenge materials must be standardized, for example, partially defatted peanut flour composed of equal amounts of the three major varieties of peanuts (Florunner, Virginia, Spanish). Challenge materials must be appropriately blinded with sensory evaluation used to confirm the adequacy of blinding. A double-blind, placebo-controlled design should be used for low-dose challenge trials. Low-dose challenge trials would begin at doses of 10 mg of the allergenic food and would continue with doses of 100 mg and 1 mg followed by specific higher doses up to 100 mg depending upon the expert judgement of the physician; even higher doses might be applied to assure that the patient is indeed reactive to the particular food. A 30-min time interval would be used between doses, and reactive doses would be expressed as both discrete and cumulative doses. The goal of each challenge would be to develop objective symptoms; trials should not be discontinued on the basis of subjective symptoms only. Statistically, a minimum of 29 patients would be enrolled in low-dose challenge trials for each allergenic food because 0 reactors out of 29 patients at a particular dose allow the conclusion that there is 95% certainty that 90% of allergic individuals will not react to that dose. Conclusion A consensus protocol was developed. Using this protocol, it will be possible to estimate threshold doses for allergenic foods, the lowest amount that elicits mild, objective symptoms in highly sensitive individuals.

Scientific Opinion on the evaluation of allergenic foods and food ingredients for labelling purposes

“…Guidelines for the standardisation of DBPCFCs and for the design and reporting of DBPCFCs for threshold-finding purposes, which generally require lower starting doses of the allergen and wider dose ranges, have been published to increase the comparability of the results among studies (BindslevJensen et al, 2004;Taylor et al, 2004;Sampson et al, 2012).…”

Teste de provocação oral aberto na confirmação de alergia ao leite de vaca mediada por IgE: qual seu valor na prática clínica?

“…Entende-se por sintomas subjetivos aqueles que podem ser influenciados por fatores psicológicos, como aversão ao alimento ou ansiedade. Como exemplos podem ser citados: dor ou desconforto abdominal, náuseas, vômito, mal-estar geral, palpitação, exacerbação de prurido cutâneo (no caso de dermatite atópica), prurido labial, prurido em orofaringe, queimação na língua, sensação de aperto na garganta, dificuldade em engolir e outros sintomas, como sonolência e irritabilidade (10,26,27) . O TPO simples cego pode ser feito com ou sem placebo, na dependência do protocolo adotado (9) .…”

Allergen Avoidance Approaches in Food Allergy Management

“…Another common example is the occurrence of peanut allergen in margarine or whole milk chocolate. The risk of allergen contamination for an allergic reaction or even life-threatening event depends on the threshold dose of an offending food eliciting adverse reactions [18] which differs between individuals, depends on food processing and the type of allergic reaction. Sicherer et al [19] reported the dose response in double-blind, placebo-controlled oral food challenges in 196 children with atopic dermatitis and known food allergy against egg, milk, soy, wheat, peanut or fish.…”