Suitability of low-dose, open food challenge data to supplement double-blind, placebo-controlled data in generation of food allergen threshold dose distributions

Eliciting and stop dose during oral food challenges for peanut and common tree nuts in different age groups

BACKGROUND

Oral food challenges (OFCs) are used to confirm or reject a diagnosis of food allergy. However, younger children may encounter difficulties in consuming all offered doses during an OFC in the absence of symptoms, resulting in inconclusive outcomes. Our aim is to assess the eliciting dose for objective symptoms among various age groups and determine the necessity of consuming the final dose step during an uneventful OFC to avoid false negative outcomes.

METHODS

OFCs for common food allergens performed between 2012 and 2019 were analyzed retrospectively. The primary outcome was the association of age with stop dose for OFCs with inconclusive outcome. Secondary outcome measures were the association of age with eliciting dose and the potential number of false negative outcomes.

RESULTS

A total of 1327 OFCs were performed in 707 patients. Of these, 514 (38.7%) were positive, 589 (44.4%) negative, and 224 (16.9%) inconclusive. In OFCs with inconclusive outcome, age appeared to be a significant predictor of the stop dose only for almond (p = .005). Objective symptoms occurred after the last dose step in 2%-13% of all OFCs with positive outcome. In our cohort, potential false negative outcomes may have been drawn in 27.6% of uneventful OFCs.

CONCLUSIONS

Two third of children under 6 years of age successfully consumed all the provided doses during OFCs with a negative outcome. The eliciting dose for objective symptoms was not associated with age, and in a substantial number of OFCs with positive outcome, symptoms occurred after eating the final dose. These findings suggest that in case of an uneventful OFC, the outcome should be drawn only after a cumulative dose of 4.4 g has been consumed to avoid the risk of a potential false negative outcome.

Sesame eliciting and safe doses in a large sesame allergic population

BACKGROUND

Sesame is a significant food allergen causing severe and even fatal reactions. Given its increasing prevalence in western diet, sesame is listed as an allergenic food requiring labeling in the United States and EU. However, data on the population reaction doses to sesame are limited.

METHODS

All sesame oral food challenges (OFCs), performed either for diagnosis or for threshold identification before the beginning of sesame oral immunotherapy (OIT) between November 2011 and July 2021 in Shamir medical center were analyzed for reaction threshold distribution. Safe-dose challenges with 90-120 min intervals were also analyzed.

RESULTS

Two hundred and fifty patients underwent 338 positive OFCs, and additional 158 safe-dose OFCs were performed. The discrete and cumulative protein amounts estimated to elicit an objective reaction in 1% (ED01) of the entire cohort (n = 250) were 0.8 mg (range 0.3-6.3) and 0.7 mg (range 0.1-7.1), respectively, and those for 5% of the population (ED05) were 3.4 mg (range 1.2-20.6) and 4.5 mg (range 1.2-28.8), respectively. Safe-dose OFCs showed similar values of ED01 (0.8, 0.4-7.5 mg) and ED05 (3.4, 1.2-22.9 mg). While doses of ≤1 mg sesame protein elicited oral pruritus in 11.6% of the patients, no objective reaction was documented to this amount in any of the challenges, including safe-dose OFCs.

CONCLUSIONS

This study provides data on sesame reaction threshold distribution in the largest population of allergic patients studied, with no right or left censored data, and with validation using a safe-dose OFC. It further supports the current methods for ED determination as appropriate for establishing safety precautions for the food industry.

A comparison of double-blind, placebo-controlled food challenge and open food challenge

BACKGROUND

Double-blind, placebo-controlled food challenge (DBPCFC) remains the gold standard for diagnosing food allergy, despite sparse comparisons to open food challenges (OpenFCs). The objective of this retrospective study was to compare severity of symptoms and threshold values (cumulative dose of food allergen eliciting a clinical reaction) in children and adults with peanut allergy, challenged in an open and/or double-blind, placebo-controlled protocol.

METHODS

This study included patients from the Allergy Centre, Odense University Hospital with a positive oral food challenge, defined as strict objective signs, with peanut during the period 2001-2022. Severity of symptoms was graded using the Sampson's severity score. Distribution models of threshold values were calculated using log-normal interval-censored survival analysis, and the number of placebo reactions was evaluated.

RESULTS

In total, 318 positive OpenFCs and 86 DBPCFCs were included. There was no difference in severity of symptoms nor threshold values comparing the two challenge types, neither when stratified for age groups. However, a higher proportion of children experienced Grade 3 symptoms in the double-blind group. Only one patient had a positive reaction to a placebo challenge.

CONCLUSION

Our findings do not advocate for DBPCFC being superior to OpenFC, if the latter is performed with strict objective stop criteria by trained staff.

Application of AllerCatPro 2.0 for protein safety assessments of consumer products

Foreign proteins are potentially immunogenic, and a proportion of these are able to induce immune responses that result in allergic sensitization. Subsequent exposure of sensitized subjects to the inducing protein can provoke a variety of allergic reactions that may be severe, or even fatal. It has therefore been recognized for some time that it is important to determine a priori whether a given protein has the potential to induce allergic responses in exposed subjects. For example, the need to assess whether transgene products expressed in genetically engineered crop plants have allergenic properties. This is not necessarily a straightforward exercise (as discussed elsewhere in this edition), but the task becomes even more challenging when there is a need to conduct an overall allergenicity safety assessment of complex mixtures of proteins in botanicals or other natural sources that are to be used in consumer products. This paper describes a new paradigm for the allergenicity safety assessment of proteins that is based on the use of AllerCatPro 2.0, a new version of a previously described web application model developed for the characterization of the allergenic potential of proteins. Operational aspects of AllerCatPro 2.0 are described with emphasis on the application of new features that provide improvements in the predictions of allergenic properties such as the identification of proteins with high allergenic concern. Furthermore, the paper provides a description of strategies of how AllerCatPro 2.0 can best be deployed as a screening tool for identifying suitable proteins as ingredients in consumer products as well as a tool, in conjunction with label-free proteomic analysis, for identifying and semiquantifying protein allergens in complex materials. Lastly, the paper discusses the steps that are recommended for formal allergenicity safety assessment of novel consumer products which contain proteins, including consideration and integration of predicted consumer exposure metrics. The article therefore provides a holistic perspective of the processes through which effective protein safety assessments can be made of potential allergenic hazards and risks associated with exposure to proteins in consumer products, with a particular focus on the use of AllerCatPro 2.0 for this purpose.

Threshold of Reactivity and Tolerance to Precautionary Allergen-Labelled Biscuits of Baked Milk- and Egg-Allergic Children

Extremely sensitive food-allergic patients may react to very small amounts of allergenic foods. Precautionary allergen labelling (PAL) warns from possible allergenic contaminations. We evaluated by oral food challenge the reactivity to a brand of PAL-labelled milk- and egg-free biscuits of children with severe milk and egg allergy. We explored the ability of proteomic methods to identify minute amounts of milk/egg allergens in such biscuits. Traces of milk and/or egg allergens in biscuits were measured by two different liquid-chromatography-mass spectrometry methods. The binding of patient’s serum with egg/milk proteins was assessed using immunoblotting. None of the patients reacted to biscuits. Egg and milk proteins were undetectable with a limit of detection of 0.6 µg/g for milk and egg (method A), and of 0.1 and 0.3 µg /g for milk and egg, respectively (method B). The immunoblots did not show milk/egg proteins in the studied biscuits. Milk/egg content of the biscuits is far lower than 4 µg of milk or egg protein per gram of product, the minimal doses considered theoretically capable of causing reactions. With high sensitivity, proteomic assessments predict the harmlessness of very small amount of allergens in foods, and can be used to help avoiding unnecessary PAL.

Mass food challenges in a vacant COVID-19 stepdown facility: Exceptional opportunity provides a model for the future

BACKGROUND

Internationally, the COVID-19 pandemic severely curtailed access to hospital facilities for those awaiting elective/semi-elective procedures. For allergic children in Ireland, already waiting up to 4 years for an elective oral food challenge (OFC), the restrictions signified indefinite delay. At the time of the initiative, there were approx 900 children on the Children's Health Ireland (CHI) waiting list. In July 2020, a project was facilitated by short-term (6 weeks) access to an empty COVID stepdown facility built, in a hotel conference centre, commandeered by the Health Service Executive (HSE), Ireland. The aim of this study was to achieve the rapid roll-out of an offsite OFC service, delivering high throughput of long waiting patients, while aligning with existing hospital policies and quality standards, international allergy guidelines and national social distancing standards.

METHODS

The working group engaged key stakeholders to rapidly develop an offsite OFC facility. Consultant paediatric allergists, consultant paediatricians, trainees and allergy clinical nurse specialists were seconded from other duties. The facility was already equipped with hospital beds, bedside monitors (BP, pulse and oxygen saturation) and bedside oxygen. All medication and supplies had to be brought from the base hospital. Daily onsite consultant anaesthetic cover was resourced and a resuscitation room equipped. Standardized food challenge protocols were created. Access to the onsite hotel chef facilitated food preparation. A risk register was established.

RESULTS

After 6 weeks of planning, the remote centre became operational on 7/9/2020, with the capacity of 27 OFC/day. 474 challenges were commenced: 465 (98%) were completed and 9 (2%) were inconclusive. 135 (29%) OFCs were positive, with 25 (5%) causing anaphylaxis. No child required advanced airway intervention. 8 children were transferred to the base hospital. The CHI allergy waiting list was reduced by almost 60% in only 24 days.

CONCLUSIONS

Oral food challenges remain a vital tool in the care of allergic children, with their cost saving and quality-of-life benefits negatively affected by a delay in their delivery. This project has shown it is possible to have huge impacts on a waiting list efficiently, effectively and safely with good planning and staff buy-in-even in a pandemic. Adoption of new, flexible and efficient models of service delivery will be important for healthcare delivery in the post-COVID-19 era.